Medicine and Health Sciences Commons^™

A Phenotypically Robust Model Of Spinal And Bulbar Muscular Atrophy In Drosophila, Kristin Richardson, Medha Sengupta, Alyson Sujkowski, Kozeta Libohova, Autumn C. Harris, Robert Wessells, Diane E. Merry, Sokol V. Todi

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is an X-linked disorder that affects males who inherit the androgen receptor (AR) gene with an abnormal CAG triplet repeat expansion. The resulting protein contains an elongated polyglutamine (polyQ) tract and causes motor neuron degeneration in an androgen-dependent manner. The precise molecular sequelae of SBMA are unclear. To assist with its investigation and the identification of therapeutic options, we report here a new model of SBMA in Drosophila melanogaster. We generated transgenic flies that express the full-length, human AR with a wild-type or pathogenic polyQ repeat. Each transgene is inserted into the same safe …

How Carvedilol Does Not Activate Β2-Adrenoceptors, Robert J. Lefkowitz, Howard A. Rockman, Paul J. Shim, Samuel Liu, Seungkirl Ahn, Biswaranjan Pani, Sudarshan Rajagopal, Sudha K. Shenoy, Michel Bouvier, Jeffrey L. Benovic, Stephen B. Liggett, Robert R. Ruffolo, Michael R. Bristow, Milton Packer

Department of Biochemistry and Molecular Biology Faculty Papers

No abstract provided.

Genetic Separation Of Brca1 Functions Reveal Mutation-Dependent Polθ Vulnerabilities, John J. Krais, David J. Glass, Ilse Chudoba, Yifan Wang, Wanjuan Feng, Dennis Simpson, Pooja Patel, Zemin Liu, Ryan Neumann-Domer, Robert G. Betsch, Andrea J. Bernhardy, Alice M. Bradbury, Jason Conger, Wei-Ting Yueh, Joseph Nacson, Richard T. Pomerantz, Gaorav P. Gupta, Joseph R. Testa, Neil Johnson

Department of Biochemistry and Molecular Biology Faculty Papers

Homologous recombination (HR)-deficiency induces a dependency on DNA polymerase theta (Polθ/Polq)-mediated end joining, and Polθ inhibitors (Polθi) are in development for cancer therapy. BRCA1 and BRCA2 deficient cells are thought to be synthetic lethal with Polθ, but whether distinct HR gene mutations give rise to equivalent Polθ-dependence, and the events that drive lethality, are unclear. In this study, we utilized mouse models with separate Brca1 functional defects to mechanistically define Brca1-Polθ synthetic lethality. Surprisingly, homozygous Brca1 mutant, Polq−/− cells were viable, but grew slowly and had chromosomal instability. Brca1 mutant cells proficient in DNA end resection were …

Development Of A Sensitive Microplate Assay For Characterizing Rna Methyltransferase Activity: Implications For Epitranscriptomics And Drug Development, Isaiah K. Mensah, Allison B. Norvil, Ming He, Emma Lendy, Nicole Hjortland, Hern Tan, Richard T. Pomerantz, Andrew Mesecar, Humaira Gowher

Department of Biochemistry and Molecular Biology Faculty Papers

RNA methylation is a ubiquitous post-transcriptional modification found in diverse RNA classes and is a critical regulator of gene expression. In this study, we used Zika virus RNA methyltransferase (MTase) to develop a highly sensitive microplate assay that uses a biotinylated RNA substrate and radiolabeled AdoMet coenzyme. The assay is fast, highly reproducible, exhibits linear progress-curve kinetics under multiple turnover conditions, has high sensitivity in competitive inhibition assays, and significantly lower background levels compared with the currently used method. Using our newly developed microplate assay, we observed no significant difference in the catalytic constants of the full-length nonstructural protein 5 …

Fan1 Removes Triplet Repeat Extrusions Via A Pcna- And Rfc-Dependent Mechanism, Ashutosh S. Phadte, Mayuri Bhatia, Hope Ebert, Haaris Abdullah, Essam Abed Elrazaq, Konstantin E. Komolov, Anna Pluciennik

Department of Biochemistry and Molecular Biology Faculty Papers

Human genome-wide association studies have identified FAN1 and several DNA mismatch repair (MMR) genes as modifiers of Huntington’s disease age of onset. In animal models, FAN1 prevents somatic expansion of CAG triplet repeats, whereas MMR proteins promote this process. To understand the molecular basis of these opposing effects, we evaluated FAN1 nuclease function on DNA extrahelical extrusions that represent key intermediates in triplet repeat expansion. Here, we describe a strand-directed, extrusion-provoked nuclease function of FAN1 that is activated by RFC, PCNA, and ATP at physiological ionic strength. Activation of FAN1 in this manner results in DNA cleavage in the vicinity …

Identification Of A Β-Arrestin-Biased Negative Allosteric Modulator For The Β2-Adrenergic Receptor, Michael Ippolito, Francesco De Pascali, Nathan Hopfinger, Konstantin E. Komolov, Daniela Laurinavichyute, Poli Adi Narayana Reddy, Leon A. Sakkal, Kyle Z. Rajkowski, Ajay P. Nayak, Justin Lee, Jordan Lee, Gaoyuan Cao, Preston S. Donover, Melvin Reichman, Stevens. An, Joseph M. Salvino, Raymond B. Penn, Roger S S. Armen, Charles P. Scott, Jeffrey L. Benovic

Department of Biochemistry and Molecular Biology Faculty Papers

Catecholamine-stimulated β2-adrenergic receptor (β2AR) signaling via the canonical Gs–adenylyl cyclase–cAMP–PKA pathway regulates numerous physiological functions, including the therapeutic effects of exogenous β-agonists in the treatment of airway disease. β2AR signaling is tightly regulated by GRKs and β-arrestins, which together promote β2AR desensitization and internalization as well as downstream signaling, often antithetical to the canonical pathway. Thus, the ability to bias β2AR signaling toward the Gs pathway while avoiding β-arrestin-mediated effects may provide a strategy to improve the functional consequences of β2AR activation. Since attempts to develop Gs-biased agonists and allosteric modulators for the β2AR have been largely unsuccessful, here we …

Increased Sirt3 Combined With Parp Inhibition Rescues Motor Function Of Sbma Mice, David R. Garcia Castro, Joseph R. Mazuk, Erin M. Heine, Daniel Simpson, R. Seth Pinches, Caroline Lozzi, Kathryn Hoffman, Phillip Morrin, Dylan Mathis, Maria V. Lebedev, Elyse Nissley, Kang Hoo Han, Tyler Farmer, Diane E. Merry, Qiang Tong, Maria Pennuto, Heather L. Montie

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease with substantial mitochondrial and metabolic dysfunctions. SBMA is caused by polyglutamine (polyQ) expansion in the androgen receptor (AR). Activating or increasing the NAD+-dependent deacetylase, SIRT3, reduced oxidative stress and death of cells modeling SBMA. However, increasing diminished SIRT3 in AR100Q mice failed to reduce acetylation of the SIRT3 target/antioxidant, SOD2, and had no effect on increased total acetylated peptides in quadriceps. Yet, overexpressing SIRT3 resulted in a trend of motor recovery, and corrected TCA cycle activity by decreasing acetylation of SIRT3 target proteins. We sought to boost blunted SIRT3 activity …

Starvation Sensing By Mycobacterial Rela/Spot Homologue Through Constitutive Surveillance Of Translation, Yunlong Li, Soneya Majumdar, Ryan Treen, Manjuli R. Sharma, Jamie Corro, Howard B. Gamper, Swati R. Manjari, Jerome Prusa, Nilesh K. Banavali, Christina L. Stallings, Ya-Ming Hou, Rajendra K. Agrawal, Anil K. Ojha

Department of Biochemistry and Molecular Biology Faculty Papers

The stringent response, which leads to persistence of nutrient-starved mycobacteria, is induced by activation of the RelA/SpoT homolog (Rsh) upon entry of a deacylated-tRNA in a translating ribosome. However, the mechanism by which Rsh identifies such ribosomes in vivo remains unclear. Here, we show that conditions inducing ribosome hibernation result in loss of intracellular Rsh in a Clp protease-dependent manner. This loss is also observed in nonstarved cells using mutations in Rsh that block its interaction with the ribosome, indicating that Rsh association with the ribosome is important for Rsh stability. The cryo-EM structure of the Rsh-bound 70S ribosome in …

Changes In Nascent Chromatin Structure Regulate Activation Of The Pro-Fibrotic Transcriptome And Myofibroblast Emergence In Organ Fibrosis, Morgan D. Basta, Svetlana Petruk, Ross Summer, Joel Rosenbloom, Peter J. Wermuth, Edward J. Macarak, Alex V. Levin, Alexander Mazo, Janice L. Walker

Department of Biochemistry and Molecular Biology Faculty Papers

Cell reprogramming to a myofibroblast responsible for the pathological accumulation of extracellular matrix is fundamental to the onset of fibrosis. Here, we explored how condensed chromatin structure marked by H3K72me3 becomes modified to allow for activation of repressed genes to drive emergence of myofibroblasts. In the early stages of myofibroblast precursor cell differentiation, we discovered that H3K27me3 demethylase enzymes UTX/KDM6B creates a delay in the accumulation of H3K27me3 on nascent DNA revealing a period of decondensed chromatin structure. This period of decondensed nascent chromatin structure allows for binding of pro-fibrotic transcription factor, Myocardin-related transcription factor A (MRTF-A) to nascent DNA. …

Candidate Variants In Dna Replication And Repair Genes In Early-Onset Renal Cell Carcinoma Patients Referred For Germline Testing, Elena V. Demidova, Ilya G. Serebriiskii, Ramilia Vlasenkova, Simon Kelow, Mark D. Andrake, Tiffiney R. Hartman, Tatiana Kent, James Virtucio, Gail L. Rosen, Richard T. Pomerantz, Roland L. Dunbrack, Erica A. Golemis, Michael J. Hall, David Y.T. Chen, Mary B. Daly, Sanjeevani Arora

Department of Biochemistry and Molecular Biology Faculty Papers

Background: Early-onset renal cell carcinoma (eoRCC) is typically associated with pathogenic germline variants (PGVs) in RCC familial syndrome genes. However, most eoRCC patients lack PGVs in familial RCC genes and their genetic risk remains undefined.

Methods: Here, we analyzed biospecimens from 22 eoRCC patients that were seen at our institution for genetic counseling and tested negative for PGVs in RCC familial syndrome genes.

Results: Analysis of whole-exome sequencing (WES) data found enrichment of candidate pathogenic germline variants in DNA repair and replication genes, including multiple DNA polymerases. Induction of DNA damage in peripheral blood monocytes (PBMCs) significantly elevated numbers of …

Protocol To Identify The Core Gene Supported By An Essential Gene In E. Coli Bacteria Using A Genome-Wide Suppressor Screen, Isao Masuda, Ya-Ming Hou

Department of Biochemistry and Molecular Biology Faculty Papers

We describe here a genome-wide screening approach to identify the most critical core reaction among a network of many that are supported by an essential gene to establish cell viability. We describe steps for maintenance plasmid construction, knockout cell construction, and phenotype validation. We then detail isolation of suppressors, whole-genome sequencing analysis, and reconstruction of CRISPR mutants. We focus on E. coli trmD, which encodes an essential methyl transferase that synthesizes m1G37 on the 3'-side of the tRNA anticodon. For complete details on the use and execution of this protocol, please refer to Masuda et al. (2022).

Role Of Ribosome Recycling Factor In Natural Termination And Translational Coupling As A Ribosome Releasing Factor, Yoshio Inokuchi, Fabio Quaglia, Akikazu Hirashima, Yoshihiro Yamamoto, Hideko Kaji, Akira Kaji

Department of Biochemistry and Molecular Biology Faculty Papers

The role of ribosome recycling factor (RRF) of E. coli was studied in vivo and in vitro. We used the translational coupling without the Shine-Dalgarno sequence of downstream ORF (d-ORF) as a model system of the RRF action in natural termination of protein synthesis. For the in vivo studies we used the translational coupling by the adjacent coat and lysis genes of RNA phage GA sharing the termination and initiation (UAAUG) and temperature sensitive RRF. The d-ORF translation was measured by the expression of the reporter lacZ gene connected to the 5'-terminal part of the lysis gene. The results showed …

Semi-Quantitative Detection Of Pseudouridine Modifications And Type I/Ii I/Ii Hypermodifications In Human Mrnas Using Direct Long-Read Sequencing, Sepideh Tavakoli, Mohammad Nabizadeh, Amr Makhamreh, Howard Gamper, Caroline A Mccormick, Neda K Rezapour, Ya-Ming Hou, Meni Wanunu, Sara H Rouhanifard

Department of Biochemistry and Molecular Biology Faculty Papers

Here, we develop and apply a semi-quantitative method for the high-confidence identification of pseudouridylated sites on mammalian mRNAs via direct long-read nanopore sequencing. A comparative analysis of a modification-free transcriptome reveals that the depth of coverage and specific k-mer sequences are critical parameters for accurate basecalling. By adjusting these parameters for high-confidence U-to-C basecalling errors, we identify many known sites of pseudouridylation and uncover previously unreported uridine-modified sites, many of which fall in k-mers that are known targets of pseudouridine synthases. Identified sites are validated using 1000-mer synthetic RNA controls bearing a single pseudouridine in the center position, demonstrating systematic …

Disruption Of The Interaction Between Mutationally Activated Gαq And Gβγ Attenuates Aberrant Signaling, Jenna L Aumiller, Philip B Wedegaertner

Department of Biochemistry and Molecular Biology Faculty Papers

Heterotrimeric G protein stimulation via G protein-coupled receptors promotes downstream proliferative signaling. Mutations can occur in Gα proteins which prevent GTP hydrolysis; this allows the G proteins to signal independently of G protein-coupled receptors and can result in various cancers, such as uveal melanoma (UM). Most UM cases harbor Q209L, Q209P, or R183C mutations in Gαq/11 proteins, rendering the proteins constitutively active (CA). Although it is generally thought that active, GTP-bound Gα subunits are dissociated from and signal independently of Gβγ, accumulating evidence indicates that some CA Gα mutants, such as Gαq/11, retain binding to Gβγ, and this interaction is …

Differentiating Pc12 Cells To Evaluate Neurite Densities Through Live-Cell Imaging, Jordyn Karliner, Diane E Merry

Department of Biochemistry and Molecular Biology Faculty Papers

Although PC12 cells are a valuable tool in neuroscience research, previously published PC12 cell differentiation techniques fail to consider the variability in differentiation rates between different PC12 cell strains and clonal variants. Here, we present a comprehensive protocol to differentiate PC12 cells into equivalent neurite densities through live-cell imaging for morphological, immunocytochemical, and biochemical analyses. We detail steps on optimized substrate coating, plating techniques, culture media, validation steps, and quantification techniques.

High-Resolution Cryo-Em Structure Of The Shigella Virus Sf6 Genome Delivery Tail Machine, Fenglin Li, Chun-Feng David Hou, Ruoyu Yang, Richard Whitehead, Carolyn M. Teschke, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

Sf6 is a bacterial virus that infects the human pathogen Shigella flexneri. Here, we describe the cryo–electron microscopy structure of the Sf6 tail machine before DNA ejection, which we determined at a 2.7-angstrom resolution. We built de novo structures of all tail components and resolved four symmetry-mismatched interfaces. Unexpectedly, we found that the tail exists in two conformations, rotated by ~6° with respect to the capsid. The two tail conformers are identical in structure but differ solely in how the portal and head-to-tail adaptor carboxyl termini bond with the capsid at the fivefold vertex, similar to a diamond held over …

In Silico Identification Of A Β2-Adrenoceptor Allosteric Site That Selectively Augments Canonical Β2ar-Gs Signaling And Function, Sushrut D Shah, Christoffer Lind, Francesco De Pascali, Raymond B Penn, Alexander D Mackerell, Deepak A Deshpande

Department of Biochemistry and Molecular Biology Faculty Papers

Activation of β2-adrenoceptors (β2ARs) causes airway smooth muscle (ASM) relaxation and bronchodilation, and β2AR agonists (β-agonists) are front-line treatments for asthma and other obstructive lung diseases. However, the therapeutic efficacy of β-agonists is limited by agonist-induced β2AR desensitization and noncanonical β2AR signaling involving β-arrestin that is shown to promote asthma pathophysiology. Accordingly, we undertook the identification of an allosteric site on β2AR that could modulate the activity of β-agonists to overcome these limitations. We employed the site identification by ligand competitive saturation (SILCS) computational method to comprehensively map the entire 3D structure of in silico-generated β2AR intermediate conformations and identified …

Terminase Subunits From The Pseudomonas-Phage E217, Ravi K Lokareddy, Chun-Feng David Hou, Steven G Doll, Fenglin Li, Richard E Gillilan, Francesca Forti, David S Horner, Federica Briani, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

Pseudomonas phages are increasingly important biomedicines for phage therapy, but little is known about how these viruses package DNA. This paper explores the terminase subunits from the Myoviridae E217, a Pseudomonas-phage used in an experimental cocktail to eradicate P. aeruginosa in vitro and in animal models. We identified the large (TerL) and small (TerS) terminase subunits in two genes ∼58 kbs away from each other in the E217 genome. TerL presents a classical two-domain architecture, consisting of an N-terminal ATPase and C-terminal nuclease domain arranged into a bean-shaped tertiary structure. A 2.05 Å crystal structure of the C-terminal domain revealed …

Structure Of The Pre-Mrna Leakage 39-Kda Protein Reveals A Single Domain Of Integrated Zf-C3hc And Rsm1 Modules, Hideharu Hashimoto, Daniel H. Ramirez, Ophélie Lautier, Natalie Pawlak, Günter Blobel, Benoît Palancade, Erik W. Debler

Department of Biochemistry and Molecular Biology Faculty Papers

In Saccharomyces cerevisiae, the pre-mRNA leakage 39-kDa protein (ScPml39) was reported to retain unspliced pre-mRNA prior to export through nuclear pore complexes (NPCs). Pml39 homologs outside the Saccharomycetaceae family are currently unknown, and mechanistic insight into Pml39 function is lacking. Here we determined the crystal structure of ScPml39 at 2.5 Å resolution to facilitate the discovery of orthologs beyond Saccharomycetaceae, e.g. in Schizosaccharomyces pombe or human. The crystal structure revealed integrated zf-C3HC and Rsm1 modules, which are tightly associated through a hydrophobic interface to form a single domain. Both zf-C3HC and Rsm1 modules belong to the Zn-containing BIR (Baculovirus IAP …

Mesoscale Structure-Function Relationships In Mitochondrial Transcriptional Condensates, Marina Feric, Azadeh Sarfallah, Furqan Dar, Dmitry Temiakov, Rohit V. Pappu, Tom Misteli

Department of Biochemistry and Molecular Biology Faculty Papers

In live cells, phase separation is thought to organize macromolecules into membraneless structures known as biomolecular condensates. Here, we reconstituted transcription in condensates from purified mitochondrial components using optimized in vitro reaction conditions to probe the structure-function relationships of biomolecular condensates. We find that the core components of the mt-transcription machinery form multiphasic, viscoelastic condensates in vitro. Strikingly, the rates of condensate-mediated transcription are substantially lower than in solution. The condensate-mediated decrease in transcriptional rates is associated with the formation of vesicle-like structures that are driven by the production and accumulation of RNA during transcription. The generation of RNA alters …

Viral Small Terminase: A Divergent Structural Framework For A Conserved Biological Function., Ravi K. Lokareddy, Chun-Feng David Hou, Fenglin Li, Ruoyu Yang, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

The genome packaging motor of bacteriophages and herpesviruses is built by two terminase subunits, known as large (TerL) and small (TerS), both essential for viral genome packaging. TerL structure, composition, and assembly to an empty capsid, as well as the mechanisms of ATP-dependent DNA packaging, have been studied in depth, shedding light on the chemo-mechanical coupling between ATP hydrolysis and DNA translocation. Instead, significantly less is known about the small terminase subunit, TerS, which is dispensable or even inhibitory in vitro, but essential in vivo. By taking advantage of the recent revolution in cryo-electron microscopy (cryo-EM) and building upon a …

The Role Of Ubiquitination In Spinal And Bulbar Muscular Atrophy, Medha Sengupta, Anna Pluciennik, Diane E. Merry

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative and neuromuscular genetic disease caused by the expansion of a polyglutamine-encoding CAG tract in the androgen receptor (AR) gene. The AR is an important transcriptional regulator of the nuclear hormone receptor superfamily; its levels are regulated in many ways including by ubiquitin-dependent degradation. Ubiquitination is a post-translational modification (PTM) which plays a key role in both AR transcriptional activity and its degradation. Moreover, the ubiquitin-proteasome system (UPS) is a fundamental component of cellular functioning and has been implicated in diseases of protein misfolding and aggregation, including polyglutamine (polyQ) repeat expansion diseases …

Young Transposable Elements Rewired Gene Regulatory Networks In Human And Chimpanzee Hippocampal Intermediate Progenitors, Sruti Patoori, Samantha M Barnada, Christopher Large, John I Murray, Marco Trizzino

Department of Biochemistry and Molecular Biology Faculty Papers

The hippocampus is associated with essential brain functions, such as learning and memory. Human hippocampal volume is significantly greater than expected compared with that of non-human apes, suggesting a recent expansion. Intermediate progenitors, which are able to undergo multiple rounds of proliferative division before a final neurogenic division, may have played a role in evolutionary hippocampal expansion. To investigate the evolution of gene regulatory networks underpinning hippocampal neurogenesis in apes, we leveraged the differentiation of human and chimpanzee induced pluripotent stem cells into TBR2 (or EOMES)-positive hippocampal intermediate progenitor cells (hpIPCs). We found that the gene networks active in hpIPCs …

Enhanced Membrane Binding Of Oncogenic G Protein Αqq209l Confers Resistance To Inhibitor Ym-254890, Clinita E. Randolph, Morgan B. Dwyer, Jenna L. Aumiller, Alethia J. Dixon, Asuka Inoue, Patrick Osei-Owusu, Philip B. Wedegaertner

Department of Biochemistry and Molecular Biology Faculty Papers

Heterotrimeric G proteins couple activated G protein-coupled receptors (GPCRs) to intracellular signaling pathways. They can also function independently of GPCR activation upon acquiring mutations that prevent GTPase activity and result in constitutive signaling, as occurs with the αqQ209L mutation in uveal melanoma. YM-254890 (YM) can inhibit signaling by both GPCR-activated WT αq and GPCR-independent αqQ209L. Although YM inhibits WT αq by binding to αq-GDP and preventing GDP/GTP exchange, the mechanism of YM inhibition of cellular αqQ209L remains to be fully understood. Here, we show that YM promotes a subcellular redistribution of αqQ209L from the plasma membrane (PM) to the cytoplasm. …

Isc10, An Inhibitor Of The Smk1 Mapk, Prevents Activation Loop Autophosphorylation And Substrate Phosphorylation Through Separate Mechanisms, Abhimannyu Rimal, Thomas M Swayne, Zeal P Kamdar, Madison A Tewey, Edward Winter

Department of Biochemistry and Molecular Biology Faculty Papers

Many eukaryotic protein kinases are activated by the intramolecular autophosphorylation of activation loop residues. Smk1 is a meiosis-specific mitogen-activated protein kinase (MAPK) in yeast that autophosphorylates its activation loop tyrosine and thereby upregulates catalytic output. This reaction is controlled by an inhibitor, Isc10, that binds the MAPK during meiosis I and an activator, Ssp2, that binds Smk1/Isc10 during meiosis II. Upon completion of the meiotic divisions, Isc10 is degraded, and Smk1 undergoes autophosphorylation to generate the high activity form of the MAPK that controls spore formation. How Isc10 inhibits Smk1 is not clear. Here, we use a bacterial coexpression/reconstitution system …

G Protein-Coupled Receptor Kinase 6 (Grk6) Regulates Insulin Processing And Secretion Via Effects On Proinsulin Conversion To Insulin, Matthew J Varney, Wouter Steyaert, Paul J Coucke, Joris R Delanghe, David E Uehling, Babu Joseph, Richard Marcellus, Rima Al-Awar, Jeffrey L Benovic

Department of Biochemistry and Molecular Biology Faculty Papers

Recent studies identified a missense mutation in the gene coding for G protein-coupled receptor kinase 6 (GRK6) that segregates with type 2 diabetes (T2D). To better understand how GRK6 might be involved in T2D, we used pharmacological inhibition and genetic knockdown in the mouse β-cell line, MIN6, to determine whether GRK6 regulates insulin dynamics. We show inhibition of GRK5 and GRK6 increased insulin secretion but reduced insulin processing while GRK6 knockdown revealed these same processing defects with reduced levels of cellular insulin. GRK6 knockdown cells also had attenuated insulin secretion but enhanced proinsulin secretion consistent with decreased processing. In support …

Neuromuscular Junction Pathology Is Correlated With Differential Motor Unit Vulnerability In Spinal And Bulbar Muscular Atrophy, Elana Molotsky, Y Liu, Andrew P Lieberman, Diane E Merry

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is an X-linked, neuromuscular neurodegenerative disease for which there is no cure. The disease is characterized by a selective decrease in fast-muscle power (e.g., tongue pressure, grip strength) accompanied by a selective loss of fast-twitch muscle fibers. However, the relationship between neuromuscular junction (NMJ) pathology and fast-twitch motor unit vulnerability has yet to be explored. In this study, we used a cross-model comparison of two mouse models of SBMA to evaluate neuromuscular junction pathology, glycolytic-to-oxidative fiber-type switching, and cytoskeletal alterations in pre- and postsynaptic termini of tibialis anterior (TA), gastrocnemius, and soleus hindlimb muscles. …

Regulating Phase Transition In Neurodegenerative Diseases By Nuclear Import Receptors, Amandeep Girdhar, Lin Guo

Department of Biochemistry and Molecular Biology Faculty Papers

RNA-binding proteins (RBPs) with a low-complexity prion-like domain (PLD) can undergo aberrant phase transitions and have been implicated in neurodegenerative diseases such as ALS and FTD. Several nuclear RBPs mislocalize to cytoplasmic inclusions in disease conditions. Impairment in nucleocytoplasmic transport is another major event observed in ageing and in neurodegenerative disorders. Nuclear import receptors (NIRs) regulate the nucleocytoplasmic transport of different RBPs bearing a nuclear localization signal by restoring their nuclear localization. NIRs can also specifically dissolve or prevent the aggregation and liquid–liquid phase separation of wild-type or disease-linked mutant RBPs, due to their chaperoning activity. This review focuses on …

Recognition Of The Tdp-43 Nuclear Localization Signal By Importin Α1/Β, Steven G Doll, Hamed Meshkin, Alexander J Bryer, Fenglin Li, Ying-Hui Ko, Ravi K Lokareddy, Richard E Gillilan, Kushol Gupta, Juan R Perilla, Gino Cingolani

Department of Biochemistry and Molecular Biology Faculty Papers

Cytoplasmic mislocalization of the TAR-DNA binding protein of 43 kDa (TDP-43) leads to large, insoluble aggregates that are a hallmark of amyotrophic lateral sclerosis and frontotemporal dementia. Here, we study how importin α1/β recognizes TDP-43 bipartite nuclear localization signal (NLS). We find that the NLS makes extensive contacts with importin α1, especially at the minor NLS-binding site. NLS binding results in steric clashes with the C terminus of importin α1 that disrupts the TDP-43 N-terminal domain (NTD) dimerization interface. A putative phosphorylation site in the proximity of TDP-43 R83 at the minor NLS site destabilizes binding to importins by reducing …

Genomic Features Underlie The Co-Option Of Sva Transposons As Cis-Regulatory Elements In Human Pluripotent Stem Cells, Samantha M Barnada, Andrew Isopi, Daniela Tejada-Martinez, Clément Goubert, Sruti Patoori, Luca Pagliaroli, Mason Tracewell, Marco Trizzino

Department of Biochemistry and Molecular Biology Faculty Papers

Domestication of transposable elements (TEs) into functional cis-regulatory elements is a widespread phenomenon. However, the mechanisms behind why some TEs are co-opted as functional enhancers while others are not are underappreciated. SINE-VNTR-Alus (SVAs) are the youngest group of transposons in the human genome, where ~3,700 copies are annotated, nearly half of which are human-specific. Many studies indicate that SVAs are among the most frequently co-opted TEs in human gene regulation, but the mechanisms underlying such processes have not yet been thoroughly investigated. Here, we leveraged CRISPR-interference (CRISPRi), computational and functional genomics to elucidate the genomic features that underlie SVA domestication …