YY1 is a developmentally important transcription factor that regulates expression of numerous genes. The Drosophila Polycomb group (PcG) protein, Pleiohomeotic (PHO), bears sequence homology with YY1. We found that YY1 can functionally replace PHO as a PcG protein in vivo. YY1 expression in Drosophila results in PcG-dependent transcriptional repression and rescue of pho mutant flies. DNA binding by YY1 causes recruitment of PcG proteins and modification of histones by deacetylation and methylation. We found that YY1 sequences 201-226, when linked to the GAL4 DNA binding domain are necessary and sufficient for transcriptional repression. These YY1 residues physically interact with CtBP, PCNA and SUMO-1. We will address the following questions concerning YY1 PcG function: 1) What is the mechanism of PcG transcriptional repression by YY1? By ChIP assay we will determine the YY1 sequences needed for PcG recruitment to DNA and histone modification. In vivo rescue experiments will determine the sequences needed for organismal development. Genetic and ChIP approaches will determine the importance of PCNA, CtBP and SUMO-1 in YY1 medicated PcG repression. We will also explore the temporal requirements of YY1 DNA binding, PcG recruitment, and histone modification. 2) What is the mechanism of CtBP function in YY1 DNA binding and PcG repression? CtBP mutation results in reduced YY1 DNA binding and PcG recruitment in vivo. We will determine the effect of CtBP mutation on YY1 stability, DNA binding ability, intracellular location, and possible sequestration into a complex. EMSA and GST pull-down studies will explore the importance of CtBP sumoylation for interaction with YY1. We will use ChIP assays to characterize PcG binding to numerous PREs that bind to YY1. 3) How does YY1 function in mammalian PcG repression systems? A number of candidate mammalian PRE sequences have been identified that bind YY1 and other PcG proteins. We will use ChIP studies to determine whether CtBP, PCNA, or sumoylated proteins bind to mammalian PREs. We will use overexpression and RNAi knock-down of YY1, CtBP, SUMO-1 and PCNA to explore the effects on PcG recruitment, histone modification, and gene expression. PcG proteins are also implicated in muscle differentiation. Therefore, we will test the roles of YY1, CtBP, SUMO-1, and PCNA in differentation of myblasts into myotubes. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM071830-02
Application #
7210627
Study Section
Development - 1 Study Section (DEV)
Program Officer
Tompkins, Laurie
Project Start
2006-04-01
Project End
2010-03-31
Budget Start
2007-04-01
Budget End
2008-03-31
Support Year
2
Fiscal Year
2007
Total Cost
$264,745
Indirect Cost
Name
University of Pennsylvania
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Pan, Xuan; Jones, Morgan; Jiang, Jie et al. (2012) Increased expression of PcG protein YY1 negatively regulates B cell development while allowing accumulation of myeloid cells and LT-HSC cells. PLoS One 7:e30656
Hodawadekar, Suchita; Park, Kyoungsook; Farrar, Michael A et al. (2012) A developmentally controlled competitive STAT5-PU.1 DNA binding mechanism regulates activity of the Ig ? E3' enhancer. J Immunol 188:2276-84
Atchison, Michael; Basu, Arindam; Zaprazna, Kristina et al. (2011) Mechanisms of Yin Yang 1 in oncogenesis: the importance of indirect effects. Crit Rev Oncog 16:143-61
Basu, Arindam; Atchison, Michael L (2010) CtBP levels control intergenic transcripts, PHO/YY1 DNA binding, and PcG recruitment to DNA. J Cell Biochem 110:62-9
Wilkinson, Frank; Pratt, Heather; Atchison, Michael L (2010) PcG recruitment by the YY1 REPO domain can be mediated by Yaf2. J Cell Biochem 109:478-86
Wei, Fang; Zaprazna, Kristina; Wang, Junwen et al. (2009) PU.1 can recruit BCL6 to DNA to repress gene expression in germinal center B cells. Mol Cell Biol 29:4612-22
Wilkinson, Frank H; Park, Kyoungsook; Atchison, Michael L (2006) Polycomb recruitment to DNA in vivo by the YY1 REPO domain. Proc Natl Acad Sci U S A 103:19296-301