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Full-Text Articles in Molecular Biology

Maelstrom Represses Canonical Rna Polymerase Ii Transcription In Drosophila Dual-Strand Pirna Clusters, Timothy H. Chang Apr 2018

Maelstrom Represses Canonical Rna Polymerase Ii Transcription In Drosophila Dual-Strand Pirna Clusters, Timothy H. Chang

GSBS Dissertations and Theses

Transposons constitute much of the animal genome. While many transposons are ancient and inactivated, numerous others are intact and must be actively repressed. Uncontrolled transposons can cause genomic instability through DNA damage or mutations and must be carefully silenced in the germline or risk sterility or mutations that are passed on to offspring.

In Drosophila melanogaster, 23–30 nt long piRNAs direct transposon silencing by serving as guides for Aubergine, Argonaute3, and Piwi, the three fly PIWI proteins. piRNAs derive from piRNA clusters—large heterochromatic DNA loci comprising transposons and transposon fragments. piRNAs are loaded into PIWI proteins via the ...


Gcn5 Impacts Fgf Signaling At Multiple Levels And Activates C-Myc Target Genes During Early Differentiation Of Embryoid Bodies, Li Wang Aug 2017

Gcn5 Impacts Fgf Signaling At Multiple Levels And Activates C-Myc Target Genes During Early Differentiation Of Embryoid Bodies, Li Wang

UT GSBS Dissertations and Theses (Open Access)

Precise control of gene expression during development is orchestrated by transcription factors, signaling pathways and co-regulators, with complex cross-regulatory events often occurring. Growing evidence has identified chromatin modifiers as important regulators for development as well, yet how particular chromatin modifying enzymes affect specific developmental processes remains largely unclear. Embryonic stem cells (ESCs) are self-renewing, pluripotent, and have the abilities to generate almost all cell types in adult tissues. The dual capacity of ESCs to self-renew and differentiate offers unlimited potential for studying gene regulation events at specific developmental stages in vitro that parallel developmental events during embryogenesis in vivo.

In ...


Three-Dimensional Folding Of Eukaryotic Genomes, Tsung-Han S. Hsieh May 2017

Three-Dimensional Folding Of Eukaryotic Genomes, Tsung-Han S. Hsieh

GSBS Dissertations and Theses

Chromatin packages eukaryotic genomes via a hierarchical series of folding steps, encrypting multiple layers of epigenetic information, which are capable of regulating nuclear transactions in response to complex signals in environment. Besides the 1-dimensinal chromatin landscape such as nucleosome positioning and histone modifications, little is known about the secondary chromatin structures and their functional consequences related to transcriptional regulation and DNA replication. The family of chromosomal conformation capture (3C) assays has revolutionized our understanding of large-scale chromosome folding with the ability to measure relative interaction probability between genomic loci in vivo. However, the suboptimal resolution of the typical 3C techniques ...


The Cdk-Resistant Prb-E2f1 Complex Recruits Chromatin-Organizing Proteins To Repetitive Dna Sequences, Charles A. Ishak Apr 2017

The Cdk-Resistant Prb-E2f1 Complex Recruits Chromatin-Organizing Proteins To Repetitive Dna Sequences, Charles A. Ishak

Electronic Thesis and Dissertation Repository

This thesis investigates mechanistic links between genome integrity and the recruitment of chromatin organizing proteins to repetitive DNA sequences mediated by the retinoblastoma tumor suppressor protein (pRB). I demonstrate that a CDK-resistant interaction between the pRB C-terminus and the E2F1 coiled-coil marked box domain establishes a scaffold that facilitates recruitment of multiple chromatin-organizing proteins to repetitive sequences across the genome throughout the cell cycle. Specifically, pRB recruits the enhancer-of-zeste-homologue 2 (EZH2) histone methyltransferase to establish repressive facultative heterochromatin at repetitive sequences, and the Condensin II complex to ensure proper DNA replication and mitotic progression. To disrupt the CDK-resistant pRB-E2F1 interaction ...


Mechanisms And Dynamics Of Oxidative Dna Damage Repair In Nucleosomes, Wendy J. Cannan Jan 2016

Mechanisms And Dynamics Of Oxidative Dna Damage Repair In Nucleosomes, Wendy J. Cannan

Graduate College Dissertations and Theses

DNA provides the blueprint for cell function and growth, as well as ensuring continuity from one cell generation to the next. In order to compact, protect, and regulate this vital information, DNA is packaged by histone proteins into nucleosomes, which are the fundamental subunits of chromatin. Reactive oxygen species, generated by both endogenous and exogenous agents, can react with DNA, altering base chemistry and generating DNA strand breaks. Left unrepaired, these oxidation products can result in mutations and/or cell death. The Base Excision Repair (BER) pathway exists to deal with damaged bases and single-stranded DNA breaks. However, the packaging ...


The Mitotic Genome: Accessibility And Transcriptional Control, Chris Hsiung Jan 2016

The Mitotic Genome: Accessibility And Transcriptional Control, Chris Hsiung

Publicly Accessible Penn Dissertations

Mitosis entails dramatic global alterations to genome structure and regulation, including

chromosome condensation, dissociation of the transcriptional machinery from chromosomes, and transcriptional silencing. Here I report studies that address the macromolecular accessibility of the mitotic genome and the control of transcriptional reactivation upon mitotic exit in a mammalian cell line. The results obtained from measuring the sensitivity of chromatin to DNase I cleavage by sequencing (DNase-seq) in pure mitotic cell populations demonstrate that macromolecular accessibility of the mitotic genome is widely preserved. Thus, steric hindrance from chromatin condensation is insufficient for explaining the eviction of transcription factors from mitotic chromatin ...


Interplay Between P53 And Epigenetic Pathways In Cancer, Jiajun Zhu Jan 2016

Interplay Between P53 And Epigenetic Pathways In Cancer, Jiajun Zhu

Publicly Accessible Penn Dissertations

The human TP53 gene encodes the most potent tumor suppressor protein p53. More than half of all human cancers contain mutations in the TP53 gene, while the majority of the remaining cases involve other mechanisms to inactivate wild-type p53 function. In the first part of my dissertation research, I have explored the mechanism of suppressed wild-type p53 activity in teratocarcinoma. In the teratocarcinoma cell line NTera2, we show that wild-type p53 is mono-methylated at Lysine 370 and Lysine 382. These post-translational modifications contribute to the compromised tumor suppressive activity of p53 despite a high level of wild-type protein in NTera2 ...


Introducing Multiple Sites Of Acetylation To Histone H3 Via Nonsense Suppression, Isaac Young Jan 2016

Introducing Multiple Sites Of Acetylation To Histone H3 Via Nonsense Suppression, Isaac Young

Graduate Theses and Dissertations

A common post-translational modification (PTM) of proteins is lysine acetylation. This is an especially ubiquitous PTM in the histones of chromatin, and is important for helping to regulate both structural and mechanistic aspects of chromatin. The fundamental unit of chromatin is called the nucleosome and is made up of DNA that wraps around a histone protein octamer. Protruding from the nucleosome are 10 unstructured “tails” which protrude into the aqueous environment. A number of strategies exist for generating acetylated nucleosomes for the in-vitro study of chromatin including: Purification from eukaryotic organisms, chemical acetylation, amino acid analog incorporation, enzyme mediated acetylation ...


Rna Exosome & Chromatin: The Yin & Yang Of Transcription: A Dissertation, Mayuri Rege Nov 2015

Rna Exosome & Chromatin: The Yin & Yang Of Transcription: A Dissertation, Mayuri Rege

GSBS Dissertations and Theses

Eukaryotic genomes can produce two types of transcripts: protein-coding and non-coding RNAs (ncRNAs). Cryptic ncRNA transcripts are bona fide RNA Pol II products that originate from bidirectional promoters, yet they are degraded by the RNA exosome. Such pervasive transcription is prevalent across eukaryotes, yet its regulation and function is poorly understood.

We hypothesized that chromatin architecture at cryptic promoters may regulate ncRNA transcription. Nucleosomes that flank promoters are highly enriched in two histone marks: H3-K56Ac and the variant H2A.Z, which make nucleosomes highly dynamic. These histone modifications are present at a majority of promoters and their stereotypic pattern is ...


Atp-Dependent Heterochromatin Remodeling: A Dissertation, Benjamin J. Manning Sep 2015

Atp-Dependent Heterochromatin Remodeling: A Dissertation, Benjamin J. Manning

GSBS Dissertations and Theses

Eukaryotic DNA is incorporated into the nucleoprotein structure of chromatin. This structure is essential for the proper storage, maintenance, regulation, and function of the genomes’ constituent genes and genomic sequences. Importantly, cells generate discrete types of chromatin that impart distinct properties on genomic loci; euchromatin is an open and active compartment of the genome, and heterochromatin is a restricted and inactive compartment. Heterochromatin serves many purposes in vivo, from heritably silencing key gene loci during embryonic development, to preventing aberrant DNA repeat recombination. Despite this generally repressive role, the DNA contained within heterochromatin must still be repaired and replicated, creating ...


Towards A Unified Model Of Sperm Chromatin Structure, Graham Johnson Jan 2015

Towards A Unified Model Of Sperm Chromatin Structure, Graham Johnson

Wayne State University Dissertations

Sperm possess several layers of information that are delivered to the oocyte alongside the paternal DNA. Examples of potential sperm borne molecular cues of probable use to the embryo include RNAs and local and global chromatin structure. To identify candidate sperm RNAs that likely reach the oocyte cytoplasm following fertilization patterns of transcript compartmentalization in the mature gamete were identified. Though all sperm RNAs exhibited a preferential peripheral enrichment, a subset of RNAs were identified in which this trend was reduced. These RNAs are thought to be embedded with perinuclear theca and are correlated with late spermatogenic transcription. Malat1, a ...


A Distinct Subunit Composition Of Chromatin-Bound Mediator, Eliza Foster Jan 2015

A Distinct Subunit Composition Of Chromatin-Bound Mediator, Eliza Foster

Undergraduate Honors Theses

Mediator is a multi-subunit protein complex that plays an essential role in transcription by integrating DNA-binding transcription factors (TFs) bound to the enhancer and general transcription factors (GTFs) bound to the promoter of a gene. Mediator is similar to other general transcription factors in that it associates with the promoter region of DNA and interacts with RNA polymerase II (RNAPII), but its large size and many subunits allows it to interact with both GTFs at the promoter and other TFs bound to enhancer DNA. Mediator may regulate transcription by interacting with chromatin. Mediator can exist in different structural states and ...


Chromatin Compaction And Genome Reorganization During Spermatogenesis In M. Musculus And Sporulation In S. Cerevisiae, Jessica Michelle Bryant Jan 2014

Chromatin Compaction And Genome Reorganization During Spermatogenesis In M. Musculus And Sporulation In S. Cerevisiae, Jessica Michelle Bryant

Publicly Accessible Penn Dissertations

Gametogenesis is a complex process that results in a highly differentiated gamete capable of transmitting genetic and epigenetic information to the next generation. In the cases of mammalian spermatogenesis and yeast sporulation, an extreme post-meiotic compaction of the genome is key to gamete function. While genome compaction in sperm is reliant upon a histone-to-protamine transition, yeast spores accomplish compaction with a full complement of histones. Although the mechanisms behind such striking chromatin dynamics are largely unknown, several histone variants and post-translational modifications, especially acetylation of histone H4, have been implicated in these processes. The following studies elucidate the roles of ...


Multiple Roles Of Brd4 In The Human Papillomavirus Life Cycle, Christine M. Helfer Jan 2014

Multiple Roles Of Brd4 In The Human Papillomavirus Life Cycle, Christine M. Helfer

Publicly Accessible Penn Dissertations

ABSTRACT

MULTIPLE ROLES OF BRD4 IN THE HUMAN

PAPILLOMAVIRUS LIFE CYCLE

Christine M. Helfer

Jianxin You

While human papillomavirus (HPV) vaccines protect against acquiring new infections, there is currently no antiviral treatment for eradicating persistent HPV infections. In this study, I demonstrated that the cellular chromatin binding protein, Brd4, in association with HPV E2 protein, is important for multiple HPV functions including replication, maintenance of viral genomes, and regulation of viral gene transcription. These studies suggest that the E2–Brd4 complex could be an effective target to disrupt the HPV life cycle. Using bimolecular fluorescence complementation, we demonstrate that E2 ...


The Role Of Histone H3 And H4 In Centromere Function And Genome Integrity, Payel Chaudhuri Dec 2013

The Role Of Histone H3 And H4 In Centromere Function And Genome Integrity, Payel Chaudhuri

Theses and Dissertations

Histone H2A plays an important role in chromosomal segregation among parent and daughter cells during mitosis. While it is established that this histone is important in maintaining chromosome number in cell, further work is carried out to explore the role of other histones like H3 and H4 for similar effects. A systematic study is initiated by screening a library based on mutation of different amino acid residues in these histones. This detailed screening identified specific regions within H3 and H4, which are critically important for centromeric function. These histones residing near the DNA entry/exit region of nucleosome effects the ...


Effect Of Hinge Region Phosphorylation On The Localization Of Thp1 In Tetrahymena Thermophila, Emily Bulley, Emily Wiley Jan 2013

Effect Of Hinge Region Phosphorylation On The Localization Of Thp1 In Tetrahymena Thermophila, Emily Bulley, Emily Wiley

Scripps Senior Theses

Within the cell nucleus, there are regions of highly condensed, transcriptionally silent chromatin called heterochromatin. Heterochromatin plays an important role in both chromosomal stability and gene regulation within the cell. Heterochromatin assembly is mediated by Heterochromatin Protein 1 (HP1) binding to epigenetically marked histone tails, most notably methylated H3K9. HP1 is post-translationally phosphorylated at serine and threonine residues, and this phosphorylation has been shown to increase HP1’s binding affinity for methylated H3K9 and heterochromatin formation. To study the effect of phosphorylation on heterochromatin assembly and HP1 localization within the nucleus, the unicellular protozoan Tetrahymena thermophila was used. Tetrahymena is ...


The Role Of Centromeric Chromatin And Kinetochore-Associated Factors In Chromosome Segregation, Wesley Williamson Dec 2012

The Role Of Centromeric Chromatin And Kinetochore-Associated Factors In Chromosome Segregation, Wesley Williamson

Theses and Dissertations

Previous work in our lab has identified a point mutation in HTA1, one of the genes encoding histone H2A, which causes an increase-in-ploidy phenotype in Saccharomyces cerevisiae. This histone mutant strain was used to carry out a transposon insertion screen to identify suppressors of the increase-in-ploidy phenotype. This screen identified all three subunits of the Hda histone deacetylase complex, HDA1, HDA2, and HDA3. This study aims to elucidate the function of the Hda complex in chromosome segregation by exploring interactions among the members of the complex, as well as interactions between Hda complex and kinetochore components. We find that the ...


Characterization Of Novel Histone H2b Mutants Associated With Chromosome Segregation Defects In Saccharomyces Cerevisiae, Thiruchelvam Rajagopal May 2012

Characterization Of Novel Histone H2b Mutants Associated With Chromosome Segregation Defects In Saccharomyces Cerevisiae, Thiruchelvam Rajagopal

Theses and Dissertations

Histones are small basic proteins that associate with DNA to form the basic unit of chromatin, the nucleosome. Histones H3 and H4 form a tetramer that is bound by two H2A-H2B dimers to form the histone octamer, to which approximately 146 bp of DNA wrap around to form the nucleosome. High resolution structural information and recent advances in the understanding of histone post-translational modifications have illuminated the many regulatory functions chromatin exerts in the cell, from the transcriptional control of gene expression to chromosome segregation. However, the specific role that histones play in these processes is not well understood. Previous ...


Lysine Post-Translational Modifications Of Saccharomyces Cerevisiae Chromatin Proteins, Christopher Richard Edwards Jan 2012

Lysine Post-Translational Modifications Of Saccharomyces Cerevisiae Chromatin Proteins, Christopher Richard Edwards

Publicly Accessible Penn Dissertations

DNA exists within the cell as part of a complex structure called chromatin which is comprised of many proteins, including histones, and participates in and influences every DNA-related process. Chromatin's proteins are modified post-translationally and this impacts their functions and in turn, the DNA processes in which they participate. However, the repertoire of post-translational modifications (PTMs), the enzymes that create and remove them, and their roles in chromosome biology are not fully understood. We have used the budding yeast Saccharomyces cerevisiae to investigate chromatin PTMs, specifically lysine modifications, through three avenues: the enzymes that regulate lysine PTMs, the histone ...


Novel Roles For The Transcriptional Repressor Prdm1 In Human Natural Killer Cells And Identification Of An Inhibitor Of Its Interacting Methyltransferase G9a, Matthew Adams Smith Jan 2011

Novel Roles For The Transcriptional Repressor Prdm1 In Human Natural Killer Cells And Identification Of An Inhibitor Of Its Interacting Methyltransferase G9a, Matthew Adams Smith

Graduate Theses and Dissertations

The studies presented within this dissertation provide the first description of PRDM1 (also known as Blimp-1 or PRDI-BF1) function in natural killer cells. NK cells are major effectors of the innate immune response via antigen-independent cytotoxicity and link to the adaptive immune response through cytokine release. Molecular mechanisms mediating NK activation are relatively well-studied; however, much less is known about the mechanisms that restrain activation.

In the first study, the transcriptional repressor PRDM1 is shown to be a critical negative regulator of NK function. Microarray analysis was used to characterize transcriptional changes associated with cytokine-mediated activation. PRDM1 is expressed at ...