Affiliation:
1. Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275
2. Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
Abstract
ABSTRACT
The Extra sex combs (ESC) protein is a Polycomb group (PcG) repressor that is a key noncatalytic subunit in the ESC-Enhancer of zeste [E(Z)] histone methyltransferase complex. Survival of
esc
homozygotes to adulthood based solely on maternal product and peak ESC expression during embryonic stages indicate that ESC is most critical during early development. In contrast, two other PcG repressors in the same complex, E(Z) and Suppressor of zeste-12 [SU(Z)12], are required throughout development for viability and
Hox
gene repression. Here we describe a novel fly PcG repressor, called ESC-Like (ESCL), whose biochemical, molecular, and genetic properties can explain the long-standing paradox of ESC dispensability during postembryonic times. Developmental Western blots show that ESCL, which is 60% identical to ESC, is expressed with peak abundance during postembryonic stages. Recombinant complexes containing ESCL in place of ESC can methylate histone H3 with activity levels, and lysine specificity for K27, similar to that of the ESC-containing complex. Coimmunoprecipitations show that ESCL associates with E(Z) in postembryonic cells and chromatin immunoprecipitations show that ESCL tracks closely with E(Z) on
Ubx
regulatory DNA in wing discs. Furthermore, reduced
escl
+
dosage enhances
esc
loss-of-function phenotypes and double RNA interference knockdown of ESC/ESCL in wing disc-derived cells causes
Ubx
derepression. These results suggest that ESCL and ESC have similar functions in E(Z) methyltransferase complexes but are differentially deployed as development proceeds.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
34 articles.
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