title: Comparative analysis of chromatin binding by Sex Comb on Midleg (SCM) and other polycomb group repressors at a Drosophila Hox gene.
abstract: Sex Comb on Midleg (SCM) is a transcriptional repressor in the Polycomb group (PcG), but its molecular role in PcG silencing is not known. Although SCM can interact with Polycomb repressive complex 1 (PRC1) in vitro, biochemical studies have indicated that SCM is not a core constituent of PRC1 or PRC2. Nevertheless, SCM is just as critical for Drosophila Hox gene silencing as canonical subunits of these well-characterized PcG complexes. To address functional relationships between SCM and other PcG components, we have performed chromatin immunoprecipitation studies using cultured Drosophila Schneider line 2 (S2) cells and larval imaginal discs. We find that SCM associates with a Polycomb response element (PRE) upstream of the Ubx gene which also binds PRC1, PRC2, and the DNA-binding PcG protein Pleiohomeotic (PHO). However, SCM is retained at this Ubx PRE despite genetic disruption or knockdown of PHO, PRC1, or PRC2, suggesting that SCM chromatin targeting does not require prior association of these other PcG components. Chromatin immunoprecipitations (IPs) to test the consequences of SCM genetic disruption or knockdown revealed that PHO association is unaffected, but reduced levels of PRE-bound PRC2 and PRC1 were observed. We discuss these results in light of current models for recruitment of PcG complexes to chromatin targets.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Liangjun
authors.initials: L
authors.lastname: Wang
authors.forename: Neal
authors.initials: N
authors.lastname: Jahren
authors.forename: Ellen L
authors.initials: EL
authors.lastname: Miller
authors.forename: Carrie S
authors.initials: CS
authors.lastname: Ketel
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Mallin
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Simon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D063146:Polycomb-Group Proteins; D011485:Protein Binding; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014921:Wings, Animal / Q000033:anatomy & histology / Q000502:physiology
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D063146:Polycomb-Group Proteins; D012097:Repressor Proteins; C099357:SCM protein, Drosophila; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; C113295:pho protein, Drosophila