title: The relationship between long-range chromatin occupancy and polymerization of the Drosophila ETS family transcriptional repressor Yan.
abstract: ETS family transcription factors are evolutionarily conserved downstream effectors of Ras/MAPK signaling with critical roles in development and cancer. In Drosophila, the ETS repressor Yan regulates cell proliferation and differentiation in a variety of tissues; however, the mechanisms of Yan-mediated repression are not well understood and only a few direct target genes have been identified. Yan, like its human ortholog TEL1, self-associates through an N-terminal sterile α-motif (SAM), leading to speculation that Yan/TEL1 polymers may spread along chromatin to form large repressive domains. To test this hypothesis, we created a monomeric form of Yan by recombineering a point mutation that blocks SAM-mediated self-association into the yan genomic locus and compared its genome-wide chromatin occupancy profile to that of endogenous wild-type Yan. Consistent with the spreading model predictions, wild-type Yan-bound regions span multiple kilobases. Extended occupancy patterns appear most prominent at genes encoding crucial developmental regulators and signaling molecules and are highly conserved between Drosophila melanogaster and D. virilis, suggesting functional relevance. Surprisingly, although occupancy is reduced, the Yan monomer still makes extensive multikilobase contacts with chromatin, with an overall pattern similar to that of wild-type Yan. Despite its near-normal chromatin recruitment, the repressive function of the Yan monomer is significantly impaired, as evidenced by elevated target gene expression and failure to rescue a yan null mutation. Together our data argue that SAM-mediated polymerization contributes to the functional output of the active Yan repressive complexes that assemble across extended stretches of chromatin, but does not directly mediate recruitment to DNA or chromatin spreading.
authors.affiliation: Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Jemma L
authors.initials: JL
authors.lastname: Webber
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Lauren
authors.initials: L
authors.lastname: Cote
authors.forename: Pavithra
authors.initials: P
authors.lastname: Vivekanand
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Ni
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Nicolas
authors.initials: N
authors.lastname: Nègre
authors.forename: Richard W
authors.initials: RW
authors.lastname: Carthew
authors.forename: Kevin P
authors.initials: KP
authors.lastname: White
authors.forename: Ilaria
authors.initials: I
authors.lastname: Rebay
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002843:Chromatin / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D049750:Genome, Insect; D009154:Mutation; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C076188:AOP protein, Drosophila; D002843:Chromatin; D029721:Drosophila Proteins; D005136:Eye Proteins; D012097:Repressor Proteins