title: Transient requirements of YY1 expression for PcG transcriptional repression and phenotypic rescue.
abstract: A hallmark of PcG transcriptional repression is stability of the repressed state, although the mechanism of this stability is unclear. The mammalian transcription factor YY1 can function as a PcG protein in Drosophila resulting in transcriptional repression and correction of phenotypic defects caused by mutation of its homologue, Pleiohomeotic (PHO). To discern the temporal requirements of YY1 expression for these functions, and to study its mechanism of stable repression in vivo, we used a Drosophila larval wing imaginal disc transcriptional repression system. We found that YY1 was needed transiently at day 3 or later of embryonic development to stably repress a reporter transgene at day 8 in wing imaginal discs. Stable transcriptional repression did not correlate with maintenance of YY1 or Polycomb DNA binding, but did correlate with persistence of histone H3 methylation on lysine 27. We also found that YY1 expressed during the first 7 days of development was sufficient for rescue of fly development (a 14 day process) in pho mutant flies. Therefore, YY1 was transiently required for correction of fly defects and was dispensable past the pharate adult stage. Possible mechanisms of repression by YY1 are discussed.
authors.affiliation: Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Srinivasan
authors.forename: Xuan
authors.initials: X
authors.lastname: Pan
authors.forename: Michael L
authors.initials: ML
authors.lastname: Atchison
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D004330:Drosophila / Q000235:genetics / Q000254:growth & development; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D044127:Epigenesis, Genetic; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D007814:Larva / Q000235:genetics / Q000254:growth & development; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D063150:Polycomb Repressive Complex 1; D063146:Polycomb-Group Proteins; D011485:Protein Binding; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D014921:Wings, Animal / Q000254:growth & development; D050986:YY1 Transcription Factor / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C066770:Pc protein, Drosophila; D063146:Polycomb-Group Proteins; D014157:Transcription Factors; D050986:YY1 Transcription Factor; C113295:pho protein, Drosophila; D063150:Polycomb Repressive Complex 1