Epigenetic gene silencing by the SRY protein is mediated by a KRAB-O protein that recruits the KAP1 co-repressor machinery.
The sex determination transcription factor SRY is a cell fate-determining transcription factor that mediates testis differentiation during embryogenesis. It may function by repressing the ovarian determinant gene, RSPO1, action in the ovarian developmental pathway and activates genes, such as SOX9, important for testis differentiation at the onset of gonadogenesis. Further, altered expression of SRY and related SOX genes contribute to oncogenesis in many human cancers. Little is known of the mechanisms by which SRY regulates its target genes. Recently a KRAB domain protein (KRAB-O) that lacks a zinc finger motif has been demonstrated to interact with SRY and hypothesized to function as an adaptor molecule for SRY by tethering the KAP1-NuRD-SETDB1-HP1 silencing machinery to repress SRY targets. We have critically examined this hypothesis by reconstituting and characterizing SRY-KRAB-O-KAP1 interactions. These recombinant molecules can form a ternary complex by direct and high affinity interactions. The KRAB-O protein can simultaneously bind KAP1 and SRY in a noncompetitive but also noncooperative manner. An extensive mutagenesis analysis suggests that different surfaces on KRAB-O are utilized for these independent interactions. Transcriptional repression by SRY requires binding to KRAB-O, thus bridging to the KAP1 repression machinery. This repression machinery is recruited to SRY target promoters in chromatin templates via SRY. These results suggest that SRY has co-opted the KRAB-O protein to recruit the KAP1 repression machinery to sex determination target genes. Other KRAB domain proteins, which lack a zinc finger DNA-binding motif, may function in similar roles as adaptor proteins for epigenetic gene silencing.
Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
Hongzhuang
H
Peng
Alexey V
AV
Ivanov
Hyun J
HJ
Oh
Yun-Fai C
YF
Lau
Frank J
FJ
Rauscher
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D008297:Male; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology; D011496:Protein Methyltransferases / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism; D051876:Sex-Determining Region Y Protein / Q000235:genetics / Q000378:metabolism*; D019699:Thrombospondins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*; D000076183:Tripartite Motif-Containing Protein 28; D000098907:R-Spondins
D002352:Carrier Proteins; D002843:Chromatin; D011495:Histone-Lysine N-Methyltransferase; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex; D009687:Nuclear Proteins; D011496:Protein Methyltransferases; D012097:Repressor Proteins; D055758:SOX9 Transcription Factor; D051876:Sex-Determining Region Y Protein; D019699:Thrombospondins; D000076183:Tripartite Motif-Containing Protein 28; C534242:KRAB-O protein, mouse; C503243:RSPO1 protein, human; D000098907:R-Spondins; C518903:RSPO1 protein, mouse; C527932:SOX9 protein, human; C497745:SRY protein, human; C527933:Sox9 protein, mouse; C497746:Sry protein, mouse; C454062:SETDB1 protein, human; C516239:SETDB1 protein, mouse; C101116:TRIM28 protein, human; C103190:Trim28 protein, mouse