Medicine and Health Sciences Commons^™

Requirements For Pseudomonas Aeruginosa Type I-F Crispr-Cas Adaptation Determined Using A Biofilm Enrichment Assay, Gary E. Heussler, Jon L. Miller, Courtney E. Price, Alan J. Collins

Dartmouth Scholarship

CRISPR (clustered regularly interspaced short palindromic repeat)-Cas (CRISPR-associated protein) systems are diverse and found in many archaea and bacteria. These systems have mainly been characterized as adaptive immune systems able to protect against invading mobile genetic elements, including viruses. The first step in this protection is acquisition of spacer sequences from the invader DNA and incorporation of those sequences into the CRISPR array, termed CRISPR adaptation. Progress in understanding the mechanisms and requirements of CRISPR adaptation has largely been accomplished using overexpression of cas genes or plasmid loss assays; little work has focused on endogenous CRISPR-acquired immunity from viral predation. …

Herpes Simplex Virus And Interferon Signaling Induce Novel Autophagic Clusters In Sensory Neurons, Sarah Katzenell, David A. Leib

Dartmouth Scholarship

Herpes simplex virus 1 (HSV-1) establishes lifelong infection in the neurons of trigeminal ganglia (TG), cycling between productive infection and latency. Neuronal antiviral responses are driven by type I interferon (IFN) and are crucial to controlling HSV-1 virulence. Autophagy also plays a role in this neuronal antiviral response, but the mechanism remains obscure. In this study, HSV-1 infection of murine TG neurons triggered unusual clusters of autophagosomes, predominantly in neurons lacking detectable HSV-1 antigen. Treatment of neurons with IFN-β induced a similar response, and cluster formation by infection or IFN treatment was dependent upon an intact IFN-signaling pathway. The autophagic …

Iron-Dependent Gene Expression In Actinomyces Oris, Matthew P. Mulé, David Giacalone, Kayla Lawlor, Alexa Golden, Caroline Cook, Thomas Lott, Elizabeth Aksten, George A. O'Toole, Lori J. Bergeron

Dartmouth Scholarship

Actinomyces oris is a Gram-positive bacterium that has been associated with healthy and diseased sites in the human oral cavity. Most pathogenic bacteria require iron to survive, and in order to acquire iron in the relatively iron-scarce oral cavity A. oris has been shown to produce iron-binding molecules known as siderophores. The genes encoding these siderophores and transporters are thought to be regulated by the amount of iron in the growth medium and by the metal-dependent repressor, AmdR, which we showed previously binds to the promoter of proposed iron-regulated genes.

Clustered Regularly Interspaced Short Palindromic Repeat-Dependent, Biofilm-Specific Death Of Pseudomonas Aeruginosa Mediated By Increased Expression Of Phage-Related Genes, Gary E. E. Heussler, Kyle C. Cady, Katja Koeppen, Sabin Bhuju, Bruce A. Stanton, George A. O’Toole

Dartmouth Scholarship

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (CRISPR/Cas) system is an adaptive immune system present in many archaea and bacteria. CRISPR/Cas systems are incredibly diverse, and there is increasing evidence of CRISPR/Cas systems playing a role in cellular functions distinct from phage immunity. Previously, our laboratory reported one such alternate function in which the type 1-F CRISPR/Cas system of the opportunistic pathogen Pseudomonas aeruginosa strain UCBPP-PA14 (abbreviated as P. aeruginosa PA14) inhibits both biofilm formation and swarming motility when the bacterium is lysogenized by the bacteriophage DMS3. In this study, we demonstrated that the presence of just the DMS3 …

Nonreplicating, Cyst-Defective Type Ii Toxoplasma Gondii Vaccine Strains Stimulate Protective Immunity Against Acute And Chronic Infection, Barbara Andrea Fox, David J. Bzik

Dartmouth Scholarship

Live attenuated vaccine strains, such as type I nonreplicating uracil auxotroph mutants, are highly effective in eliciting lifelong immunity to virulent acute infection by Toxoplasma gondii. However, it is currently unknown whether vaccine-elicited immunity can provide protection against acute infection and also prevent chronic infection. To address this problem, we developed nonreverting, nonreplicating, live attenuated uracil auxotroph vaccine strains in the type II Δku80 genetic background by targeting the deletion of the orotidine 5′-monophosphate decarboxylase (OMPDC) and uridine phosphorylase (UP) genes. Deletion of OMPDC induced a severe uracil auxotrophy with loss of replication, loss of …

Expression Of Enteropathogenic Escherichia Coli Map Is Significantly Different Than That Of Other Type Iii Secreted Effectors In Vivo., Mai Nguyen, Jason Rizvi, Gail Hecht

Department of Medicine Faculty Papers

The enteropathogenic Escherichia coli (EPEC) locus of enterocyte effacement (LEE)-encoded effectors EspF and Map are multifunctional and have an impact on the tight junction barrier while the non-LEE-encoded proteins NleH1 and NleH2 possess significant anti-inflammatory activity. In order to address the temporal expression of these important genes in vivo, their promoters were cloned upstream of the luxCDABE operon, and luciferase expression was measured in EPEC-infected mice by bioluminescence using an in vivo imaging system (IVIS). Bioluminescent images of living mice, of excised whole intestines, and of whole intestines longitudinally opened and washed were assessed. The majority of bioluminescent bacteria localized …

Chip-Seq And In Vivo Transcriptome Analyses Of The Aspergillus Fumigatus Srebp Srba Reveals A New Regulator Of The Fungal Hypoxia Response And Virulence, Dawoon Chung, Bridget M. Barker, Charles C. Carey, Brittney Merriman

Dartmouth Scholarship

The Aspergillus fumigatus sterol regulatory element binding protein (SREBP) SrbA belongs to the basic Helix-Loop-Helix (bHLH) family of transcription factors and is crucial for antifungal drug resistance and virulence. The latter phenotype is especially striking, as loss of SrbA results in complete loss of virulence in murine models of invasive pulmonary aspergillosis (IPA). How fungal SREBPs mediate fungal virulence is unknown, though it has been suggested that lack of growth in hypoxic conditions accounts for the attenuated virulence. To further understand the role of SrbA in fungal infection site pathobiology, chromatin immunoprecipitation followed by massively parallel DNA sequencing (ChIP-seq) was …

Contribution Of The Staphylococcus Aureus Atl Am And Gl Murein Hydrolase Activities In Cell Division, Autolysis, And Biofilm Formation., Jeffrey L. Bose, Mckenzie K. Lehman, Paul D. Fey, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

The most prominent murein hydrolase of Staphylococcus aureus, AtlA, is a bifunctional enzyme that undergoes proteolytic cleavage to yield two catalytically active proteins, an amidase (AM) and a glucosaminidase (GL). Although the bifunctional nature of AtlA has long been recognized, most studies have focused on the combined functions of this protein in cell wall metabolism and biofilm development. In this study, we generated mutant derivatives of the clinical S. aureus isolate, UAMS-1, in which one or both of the AM and GL domains of AtlA have been deleted. Examination of these strains revealed that each mutant exhibited growth rates comparable …

The Lysr-Type Virulence Activator Aphb Regulates The Expression Of Genes In Vibrio Cholerae In Response To Low Ph And Anaerobiosis, Gabriela Kovacikova, Wei Lin, Karen Skorupski

Dartmouth Scholarship

AphB is a LysR-type activator that initiates the expression of the virulence cascade in Vibrio cholerae by cooperating with the quorum-sensing-regulated activator AphA at the tcpPH promoter on the Vibrio pathogenicity island (VPI). To identify the ancestral chromosomal genes in V. cholerae regulated by AphB, we carried out a microarray analysis and show here that AphB influences the expression of a number of genes that are not associated with the VPI. One gene strongly activated by AphB is cadC, which encodes the ToxR-like transcriptional activator responsible for activating the expression of lysine decarboxylase, which plays an important role in …

Modulation Of Edna Release And Degradation Affects Staphylococcus Aureus Biofilm Maturation., Ethan E. Mann, Kelly C. Rice, Blaise R. Boles, Jennifer L. Endres, Dev Ranjit, Lakshmi Chandramohan, Laura H. Tsang, Mark S. Smeltzer, Alexander R. Horswill, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

Recent studies have demonstrated a role for Staphylococcus aureus cidA-mediated cell lysis and genomic DNA release in biofilm adherence. The current study extends these findings by examining both temporal and additional genetic factors involved in the control of genomic DNA release and degradation during biofilm maturation. Cell lysis and DNA release were found to be critical for biofilm attachment during the initial stages of development and the released DNA (eDNA) remained an important matrix component during biofilm maturation. This study also revealed that an lrgAB mutant exhibits increased biofilm adherence and matrix-associated eDNA consistent with its proposed role as an …

Regulation Of The Mazef Toxin-Antitoxin Module In Staphylococcus Aureus And Its Impact On Sigb Expression, Niles P. Donegan, Ambrose L. Cheung

Dartmouth Scholarship

In Staphylococcus aureus, the sigB operon codes for the alternative sigma factor σ^Band its regulators that enable the bacteria to rapidly respond to environmental stresses via redirection of transcriptional priorities. However, a full model of σ^Bregulation in S. aureus has not yet emerged. Earlier data has suggested that mazEF, a toxin-antitoxin (TA) module immediately upstream of the sigB operon, was transcribed with the sigB operon. Here we demonstrate that the promoter P_mazE upstream of mazEF is essential for full σ^B activity and that instead of utilizing autorepression typical of TA systems, sigB …

Assembly And Development Of The Pseudomonas Aeruginosa Biofilm Matrix., Luyan Ma, Matthew Conover, Haiping Lu, Matthew R. Parsek, Kenneth W. Bayles, Daniel J. Wozniak

Journal Articles: Pathology and Microbiology

Virtually all cells living in multicellular structures such as tissues and organs are encased in an extracellular matrix. One of the most important features of a biofilm is the extracellular polymeric substance that functions as a matrix, holding bacterial cells together. Yet very little is known about how the matrix forms or how matrix components encase bacteria during biofilm development. Pseudomonas aeruginosa forms environmentally and clinically relevant biofilms and is a paradigm organism for the study of biofilms. The extracellular polymeric substance of P. aeruginosa biofilms is an ill-defined mix of polysaccharides, nucleic acids, and proteins. Here, we directly visualize …

Stromal Gene Signatures In Large-B-Cell Lymphomas., G Lenz, G Wright, S S Dave, W Xiao, J Powell, H Zhao, W Xu, B Tan, N Goldschmidt, Javeed Iqbal, Julie M. Vose, M Bast, Kai Fu, D D. Weisenburger, T C Greiner, James O. Armitage, A Kyle, L May, R D Gascoyne, J M Connors, G Troen, H Holte, S Kvaloy, D Dierickx, G Verhoef, J Delabie, E B Smeland, P Jares, A Martinez, A Lopez-Guillermo, E Montserrat, E Campo, R M Braziel, T P Miller, L M Rimsza, J R Cook, B Pohlman, J Sweetenham, R R Tubbs, R I Fisher, E Hartmann, A Rosenwald, G Ott, H-K Muller-Hermelink, D Wrench, T A Lister, E S Jaffe, W H Wilson, W C. Chan, L M Staudt

Journal Articles: Pathology and Microbiology

BACKGROUND: The addition of rituximab to combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP), or R-CHOP, has significantly improved the survival of patients with diffuse large-B-cell lymphoma. Whether gene-expression signatures correlate with survival after treatment of diffuse large-B-cell lymphoma is unclear.

METHODS: We profiled gene expression in pretreatment biopsy specimens from 181 patients with diffuse large-B-cell lymphoma who received CHOP and 233 patients with this disease who received R-CHOP. A multivariate gene-expression-based survival-predictor model derived from a training group was tested in a validation group.

RESULTS: A multivariate model created from three gene-expression signatures--termed "germinal-center B-cell," "stromal-1," and "stromal-2"--predicted …

Mgra Represses Biofilm Formation In Staphylococcus Aureus, Maria P. Trotonda, Sandeep Tamber, Guido Memmi, Ambrose L. Cheung

Dartmouth Scholarship

MgrA is a pleiotropic regulator that controls autolysis, virulence, and efflux pump activity in Staphylococcus aureus. We recently found that mgrA mutants of strains RN6390, SH1000, and MW2 also displayed enhanced biofilm formation compared with their respective parents. The biofilms formed by mgrA mutants of RN6390 and MW2 are independent of sigB and ica loci, two genetic elements that have been previously associated with biofilm formation in S. aureus. Biofilms formed by mgrA mutants are dependent on the expression of surface proteins mediated by the sortase gene srtA. Extracellular DNA was also a crucial component of the early biofilm of …

Repression Of Hla By Rot Is Dependent On Sae In Staphylococcus Aureus, Dongmei Li, Ambrose Cheung

Dartmouth Scholarship

The regulatory locus sae is a two-component system in Staphylococcus aureus that regulates many important virulence factors, including alpha-toxin (encoded by hla) at the transcriptional level. The SarA homologs Rot and SarT were previously shown to be repressors of hla in selected S. aureus backgrounds. To delineate the interaction of rot and sae and the contribution of sarT to hla expression, an assortment of rot and sae isogenic single mutants, a rot sae double mutant, and a rot sae sarT markerless triple mutant were constructed from wild-type strain COL. Using Northern blot analysis and transcriptional reporter gene green fluorescent protein, …

Leptospira Interrogans Endostatin-Like Outer Membrane Proteins Bind Host Fibronectin, Laminin And Regulators Of Complement, Brian Stevenson, Henry A. Choy, Marija Pinne, Matthew L. Rotondi, M. Clarke Miller, Edward Demoll, Peter Kraiczy, Anne E. Cooley, Trevor P. Creamer, Marc A. Suchard, Catherine A. Brissette, Ashutosh Verma, David A. Haake

Microbiology, Immunology, and Molecular Genetics Faculty Publications

The pathogenic spirochete Leptospira interrogans disseminates throughout its hosts via the bloodstream, then invades and colonizes a variety of host tissues. Infectious leptospires are resistant to killing by their hosts' alternative pathway of complement-mediated killing, and interact with various host extracellular matrix (ECM) components. The LenA outer surface protein (formerly called LfhA and Lsa24) was previously shown to bind the host ECM component laminin and the complement regulators factor H and factor H-related protein-1. We now demonstrate that infectious L. interrogans contain five additional paralogs of lenA, which we designated lenB, lenC, lenD, lenE and lenF …

Crystal Structure Of The Vibrio Cholerae Quorum-Sensing Regulatory Protein Hapr, Rukman S. De Silva, Gabriela Kovacikova, Wei Lin, Ronald K. Taylor, Karen Skorupski, F. Jon Kull

Dartmouth Scholarship

Quorum sensing in Vibrio cholerae involves signaling between two-component sensor protein kinases and the response regulator LuxO to control the expression of the master regulator HapR. HapR, in turn, plays a central role in regulating a number of important processes, such as virulence gene expression and biofilm formation. We have determined the crystal structure of HapR to 2.2-Å resolution. Its structure reveals a dimeric, two-domain molecule with an all-helical structure that is strongly conserved with members of the TetR family of transcriptional regulators. The N-terminal DNA-binding domain contains a helix-turn-helix DNA-binding motif and alteration of certain residues in this domain …

Membrane Association And Multimerization Of Tcpt, The Cognate Atpase Ortholog Of The Vibrio Cholerae Toxin-Coregulated-Pilus Biogenesis Apparatus, Shital A. Tripathi, Ronald K. Taylor

Dartmouth Scholarship

The toxin-coregulated pilus (TCP) is one of the major virulence factors of Vibrio cholerae. Biogenesis of this type 4 pilus (Tfp) requires a number of structural components encoded by the tcp operon. TcpT, the cognate putative ATPase, is required for TCP biogenesis and all TCP-mediated functions. We studied the stability and localization of TcpT in cells containing in-frame deletions in each of the tcp genes. TcpT was detectable in each of the biogenesis mutants except the ΔtcpT strain. TcpT was localized to the inner membrane (IM) in a TcpR-dependent manner. TcpR is a predicted bitopic inner membrane protein …

Clinical Implication Of Genome-Wide Profiling In Diffuse Large B-Cell Lymphoma And Other Subtypes Of B-Cell Lymphoma., Javeed Iqbal, Shantaram Joshi, Kavita N. Patel, Sofi I. Javed, Can Kucuk, Afeera Aabida, Francesco D'Amore, Kai Fu

Journal Articles: Pathology and Microbiology

The differentiation of lymphoid cells is tightly regulated by transcription factors at various stages during their development. During the maturation processes, different genomic alterations or aberrations such as chromosomal translocation, mutation and deletions may occur that can eventually result in distinct biological and clinical tumors. The different differentiation stages create heterogeneity in lymphoid malignancies, which can complicate the diagnosis. The initial diagnostic scheme for lymphoid diseases was coined by Rappaport followed by Revised European and American Classification of Lymphoid Neoplasms (REAL) and World Health Organization (WHO) classifications. These classification methods were based on histological, immunophenotypic and cytogenetic markers and widely …

Molecular Diagnosis Of Burkitt's Lymphoma., Sandeep S. Dave, Kai Fu, George W. Wright, Lloyd T. Lam, Philip Kluin, Evert-Jan Boerma, Timothy Greiner, Dennis D. Weisenburger, Andreas Rosenwald, German Ott, Hans-Konrad Müller-Hermelink, Randy D. Gascoyne, Jan Delabie, Lisa M. Rimsza, Rita M. Braziel, Thomas M. Grogan, Elias Campo, Elaine S. Jaffe, Bhavana J. Dave, Warren Sanger, M Bast, Julie M. Vose, James O. Armitage, Joseph M. Connors, Erlend B. Smeland, Stein Kvaloy, Harald Holte, Richard I. Fisher, Thomas P. Miller, Emilio Montserrat, Wyndham H. Wilson, Manisha Bahl, Hong Zhao, Liming Yang, John Powell, Richard Simon, Wing C. Chan, Louis M. Staudt

Journal Articles: Pathology and Microbiology

BACKGROUND: The distinction between Burkitt's lymphoma and diffuse large-B-cell lymphoma is crucial because these two types of lymphoma require different treatments. We examined whether gene-expression profiling could reliably distinguish Burkitt's lymphoma from diffuse large-B-cell lymphoma.

METHODS: Tumor-biopsy specimens from 303 patients with aggressive lymphomas were profiled for gene expression and were also classified according to morphology, immunohistochemistry, and detection of the t(8;14) c-myc translocation.

RESULTS: A classifier based on gene expression correctly identified all 25 pathologically verified cases of classic Burkitt's lymphoma. Burkitt's lymphoma was readily distinguished from diffuse large-B-cell lymphoma by the high level of expression of c-myc target …

Sara Positively Controls Bap-Dependent Biofilm Formation In Staphylococcus Aureus, María P. Trotonda, Adhar C. Manna, Ambrose L. Cheung, Iñigo Lasa, José R. Penadés

Dartmouth Scholarship

The biofilm-associated protein Bap is a staphylococcal surface protein involved in biofilm formation. We investigated the influence of the global regulatory locus sarA on bap expression and Bap-dependent biofilm formation in three unrelated Staphylococcus aureus strains. The results showed that Bap-dependent biofilm formation was diminished in the sarA mutants by an agr-independent mechanism. Complementation studies using a sarA clone confirmed that the defect in biofilm formation was due to the sarA mutation. As expected, the diminished capacity to form biofilms in the sarA mutants correlated with the decreased presence of Bap in the bacterial surface. Using transcriptional fusion and …

A Three-Component Regulatory System Regulates Biofilm Maturation And Type Iii Secretion In Pseudomonas Aeruginosa, Sherry L. Kuchma, John P. Connolly, George A. O'Toole

Dartmouth Scholarship

Biofilms are structured communities found associated with a wide range of surfaces. Here we report the identification of a three-component regulatory system required for biofilm maturation by Pseudomonas aeruginosa strain PA14. A transposon mutation that altered biofilm formation in a 96-well dish assay originally defined this locus, which is comprised of genes for a putative sensor histidine kinase and two response regulators and has been designated sadARS. Nonpolar mutations in any of the sadARS genes result in biofilms with an altered mature structure but do not confer defects in growth or early biofilm formation, swimming, or twitching motility. After …

Identification Of Sarv (Sa2062), A New Transcriptional Regulator, Is Repressed By Sara And Mgra (Sa0641) And Involved In The Regulation Of Autolysis In Staphylococcus Aureus, Adhar C. Manna, Susham S. Ingavale, Marybeth Maloney, Willem Van Wamel, Ambrose L. Cheung

Dartmouth Scholarship

The expression of genes involved in the pathogenesis of Staphylococcus aureus is known to be controlled by global regulatory loci, including agr, sarA, sae, arlRS, lytSR, and sarA-like genes. Here we described a novel transcriptional regulator called sarV of the SarA protein family. The transcription of sarV is low or undetectable under in vitro conditions but is significantly augmented in sarA and mgrA (norR or rat) (SA0641) mutants. The sarA and mgrA genes act as repressors of sarV expression, as confirmed by transcriptional fusion and Northern analysis data. Purified SarA and MgrA proteins bound specifically to separate regions of the …

Sadb Is Required For The Transition From Reversible To Irreversible Attachment During Biofilm Formation By Pseudomonas Aeruginosa Pa14, Nicky C. Caiazza, George A. O'Toole

Dartmouth Scholarship

Current models of biofilm formation by Pseudomonas aeruginosa propose that (i) planktonic cells become surface associated in a monolayer, (ii) surface-associated cells form microcolonies by clonal growth and/or aggregation, (iii) microcolonies transition to a mature biofilm comprised of exopolysaccharide-encased macrocolonies, and (iv) cells exit the mature biofilm and reenter the planktonic state. Here we report a new class of P. aeruginosa biofilm mutant that defines the transition from reversible to irreversible attachment and is thus required for monolayer formation. The transposon insertion carried by the sadB199 mutant was mapped to open reading frame PA5346 of P. aeruginosa PA14 and encodes …

Transcriptional Interference By Independently Regulated Genes Occurs In Any Relative Arrangement Of The Genes And Is Influenced By Chromosomal Integration Position, Susan K. Eszterhas, Eric E. Bouhassira, David I. K. Martin, Steven Fiering

Dartmouth Scholarship

Transcriptional interference is the influence, generally suppressive, of one active transcriptional unit on another unit linked in cis. Its wide occurrence in experimental systems suggests that it may also influence transcription in many loci, but little is known about its precise nature or underlying mechanisms. Here we report a study of the interaction of two nearly identical transcription units juxtaposed in various arrangements. Each reporter gene in the constructs has its own promoter and enhancer and a strong polyadenylation signal. We used recombinase-mediated cassette exchange (RMCE) to insert the constructs into previously tagged genomic sites in cultured cells. This …

Evaluation Of A Tetracycline-Inducible Promoter In Staphylococcus Aureus In Vitro And In Vivo And Its Application In Demonstrating The Role Of Sigb In Microcolony Formation, B. T. Bateman, N. P. Donegan, T. M. Jarry, M. Palma

Dartmouth Scholarship

An inducible promoter system provides a powerful tool for studying the genetic basis for virulence. A variety of inducible systems have been used in other organisms, including pXyl-xylR-inducible promoter, the pSpac-lacI system, and the arabinose-inducible P_BAD promoter, but each of these systems has limitations in its application to Staphylococcus aureus. In this study, we demonstrated the efficacy of a tetracycline-inducible promoter system in inducing gene expression in S. aureus in vitro and inside epithelial cells as well as in an animal model of infection. Using the xyl/tetO promoter::gfp_uvr fusion carried on a shuttle …

Immune Response Genes Modulate Serologic Responses To Vibrio Cholerae Tcpa Pilin Peptides, Michael D. Meeks, Terri K. Wade, Ronald K. Taylor, William F. Wade

Dartmouth Scholarship

Cholera is an enteric disease caused by Vibrio cholerae. Toxin-coregulated pilus (TCP), a type 4 pilus expressed by V. cholerae, is a cholera virulence factor that is required for host colonization. The TCP polymer is composed of subunits of TcpA pilin. Antibodies directed against TcpA are protective in animal models of cholera. While natural or recombinant forms of TcpA are difficult to purify to homogeneity, it is anticipated that synthesized TcpA peptides might serve as immunogens in a subunit vaccine. We wanted to assess the potential for effects of the immune response (Ir) gene that could complicate a peptide-based …

Proteolytic Release Of Cd44 Intracellular Domain And Its Role In The Cd44 Signaling Pathway., I Okamoto, Y Kawano, D Murakami, T Sasayama, N Araki, T Miki, A J Wong, H Saya

Department of Microbiology and Immunology Faculty Papers

CD44 is a widely distributed cell surface adhesion molecule and is implicated in diverse biological processes. However, the nature of intracellular signaling triggered by CD44 remains to be elucidated. Here, we show that CD44 undergoes sequential proteolytic cleavage in the ectodomain and intracellular domain, resulting in the release of a CD44 intracellular domain (ICD) fragment. Consequently, CD44ICD acts as a signal transduction molecule, where it translocates to the nucleus and activates transcription mediated through the 12-O-tetradecanoylphorbol 13-acetate-responsive element, which is found in numerous genes involved in diverse cellular processes. Expression of an uncleavable CD44 mutant as well as metalloprotease inhibitor …

Sars, A Sara Homolog Repressible By Agr, Is An Activator Of Protein A Synthesis In Staphylococcus Aureus, Ambrose L. Cheung, Katherine Schmidt, Brian Bateman, Adhar C. Manna

Dartmouth Scholarship

The expression of protein A (spa) is repressed by global regulatory loci sarA and agr. Although SarA may directly bind to the spa promoter to downregulate spa expression, the mechanism by which agr represses spa expression is not clearly understood. In searching for SarA homologs in the partially released genome, we found a SarA homolog, encoding a 250-amino-acid protein designated SarS, upstream of the spa gene. The expression of sarS was almost undetectable in parental strain RN6390 but was highly expressed in agr and sarA mutants, strains normally expressing high level of protein A. Interestingly, protein A …

Characterization Of Sarr, A Modulator Of Sar Expression In Staphylococcus Aureus, Adhar Manna, Ambrose L. Cheung

Dartmouth Scholarship

The expression of virulence determinants in Staphylococcus aureus is controlled by global regulatory loci (e.g., sar and agr). The sar locus is composed of three overlapping transcripts (sar P1, P3, and P2 transcripts from P1, P3, and P2 promoters, respectively), all encoding the 372-bp sarA gene. The level of SarA, the major regulatory protein, is partially controlled by the differential activation of sar promoters. We previously partially purified a ∼12 kDa protein with a DNA-specific column