Publications (3)12.12 Total impact
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ABSTRACT: Repression and activation of gene transcription involves multiprotein complexes that modify chromatin structure. The integration of these complexes at regulatory sites can be assisted by co-factors that link them to DNA-bound transcriptional regulators. In humans, one such co-factor is the herpes simplex virus host-cell factor 1 (HCF-1), which is implicated in both activation and repression of transcription. We show here that disruption of the gene encoding the Drosophila melanogaster homolog of HCF-1, dHCF, leads to a pleiotropic phenotype involving lethality, sterility, small size, apoptosis, and morphological defects. In Drosophila, repressed and activated transcriptional states of cell fate-determining genes are maintained throughout development by Polycomb Group (PcG) and Trithorax Group (TrxG) genes, respectively. dHCF mutant flies display morphological phenotypes typical of TrxG mutants and dHCF interacts genetically with both PcG and TrxG genes. Thus, dHCF inactivation enhances the mutant phenotypes of the Pc PcG as well as brm and mor TrxG genes, suggesting that dHCF possesses Enhancer of TrxG and PcG (ETP) properties. Additionally, dHCF interacts with the previously established ETP gene skd. These pleiotropic phenotypes are consistent with broad roles for dHCF in both activation and repression of transcription during fly development.PLoS ONE 01/2011; 6(12):e27479. · 4.09 Impact Factor
Article: Characterization of cis- and trans-acting elements in the imprinted human SNURF-SNRPN locus.[show abstract] [hide abstract]
ABSTRACT: The imprinted SNRPN locus is a complex transcriptional unit that encodes the SNURF and SmN polypeptides as well as multiple non-coding RNAs. SNRPN is located within the Prader-Willi and Angelman syndrome (PWS/AS) region that contains multiple imprinted genes, which are coordinately regulated by a bipartite imprinting center (IC). The SNRPN 5' region co-localizes with the PWS-IC and contains two DNase I hypersensitive sites, DHS1 at the SNRPN promoter, and DHS2 within intron 1, exclusively on the paternally inherited chromosome. We have examined DHS1 and DHS2 to identify cis- and trans-acting regulatory elements within the endogenous SNRPN 5' region. Analysis of DHS1 by in vivo footprinting and chromatin immunoprecipitation identified allele-specific interaction with multiple regulatory proteins, including NRF-1, which regulates genes involved in mitochondrial and metabolic functions. DHS2 acted as an enhancer of the SNRPN promoter and contained a highly conserved region that showed allele-specific interaction with unphosphorylated RNA polymerase II, YY1, Sp1 and NRF-1, further suggesting a key role for NRF-1 in regulation of the SNRPN locus. We propose that one or more of the regulatory elements identified in this study may also contribute to PWS-IC function.Nucleic Acids Research 02/2005; 33(15):4740-53. · 8.03 Impact Factor
Article: Identification and characterization of cis-acting elements in the regulation of imprinted gene expression [electronic resource] /[show abstract] [hide abstract]
ABSTRACT: ABSTRACT: The Prader-Willi and Angelman syndromes (PWS-AS) associated region includes a cluster of imprinted genes that are coordinately regulated by an imprinting center (IC) spanning the 5 region of the SNURF-SNRPN gene. The IC has a bipartite structure where the PWS-IC is postulated to create an active domain on the paternal allele, while the AS-IC is believed to silence the maternal allele. Also, alternative upstream SNURF-SNRPN promoters have been implicated in the AS-IC function. This project focused on identifying and characterizing cis-acting elements within the IC that may mediate IC function and/or SNURF-SNRPN promoter activity. The PWS-IC contains major nuclease hypersensitive sites (NHS1 and NSH2) associated with the SNURF-SNRPN promoter region and the 1st intron (adjacent to the IC), both specific to the paternal allele. ABSTRACT: In vivo footprint analysis of the promoter region has identified multiple factor binding sites, 4 specific to the paternal allele and 1 specific to the maternal allele, some of which affected promoter function in transient expression assays. Transient expression assays also helped to define other promoter elements in the SNURF-SNRPN 5 region and to identify a novel position-dependent and orientation-independent activator associated with NHS2. This element(s) preferentially activates the SNURF-SNRPN main and upstream promoters relative to the UBE3A and MKRN3 promoters. It appears to be a complex regulatory unit from which a subregion was mapped that sustains high levels of SNURF-SNRPN promoter activity. This subregion was also identified by sequence comparison of the intronic activator with the homologous region in mouse and contains several highly conserved sites including potential binding sites for SP1, NRF1 and YY1. ABSTRACT: In vivo and in vitro studies showed binding of YY1 to the intronic activator and its involvement in the activator function. Furthermore, recruitment of the non-processive form of RNA polymerase II to the activator was shown suggesting a possible role for the activator in the IC function by recruiting pol II and transferring it to the SNURF-SNRPN upstream promoters in the female germline and to the main promoter in the male germline/paternal allele. This transfer may be mediated by NRF-1 that was shown to bind in vivo to both the SNURF-SNRPN promoter and NHS2. Additionally YY1 may target the paternal allele to the nuclear matrix, which would account for the nuclear localization and early replication of that allele. Typescript. Text (Electronic thesis) in PDF format. System requirements: World Wide Web browser and PDF reader. Mode of access: World Wide Web. Title from title page of source document. Document formatted into pages; contains 148 pages. Thesis (Ph.D.)--University of Florida, 2004. Includes Vita. Includes bibliographical references.