T. Gutjahr et al., THE POLYCOMB-GROUP GENE, EXTRA SEX COMBS, ENCODES A NUCLEAR MEMBER OFTHE WD-40 REPEAT FAMILY, EMBO journal, 14(17), 1995, pp. 4296-4306
We have delimited the extra sex combs (esc) gene to <4 kb that include
a single transcript and are able to rescue both the maternal and zygo
tic esc phenotypes. Several mutations have been identified within the
esc transcript. In agreement with earlier genetic studies, esc is expr
essed maternally and its product is most abundant during the early emb
ryonic stages. It encodes a protein of the WD-40 repeat family, which
localizes predominantly to the nucleus. During germ band extension, it
is expressed in a stereotypic pattern of neuroblasts. We propose a mo
del in which Esc is recruited by gap proteins both to act as a corepre
ssor that competes with the TAF(II)80 coactivator to block transcripti
on and also to mediate the transition to permanent repression by Polyc
omb-group proteins.