TY - JOUR
T1 - A Drosophila ESC-E(Z) protein complex is distinct from other polycomb group complexes and contains covalently modified ESC
AU - Ng, Joyce
AU - Hart, Craig M.
AU - Morgan, Kelly
AU - Simon, Jeffrey A.
PY - 2000/5
Y1 - 2000/5
N2 - The extra sex combs (ESC) and Enhancer of zeste [E(Z)] proteins, members of the Polycomb group (PcG) of transcriptional repressors, interact directly and are coassociated in fly embryos. We report that these two proteins are components of a 600-kDa complex in embryos. Using gel filtration and affinity chromatography, we show that this complex is biochemically distinct from previously described complexes containing the PcG proteins Polyhomeotic, Polycomb, and Sex comb on midleg. In addition, we present evidence that ESC is phosphorylated in vivo and that this modified ESC is preferentially associated in the complex with E(Z). Modified ESC accumulates between 2 and 6 h of embryogenesis, which is the developmental time when esc function is first required. We find that mutations in E(z) reduce the ratio of modified to unmodified ESC in vivo. We have also generated germ line transformants that express ESC proteins bearing site-directed mutations that disrupt ESC- E(Z) binding in vitro. These mutant ESC proteins fail to provide esc function, show reduced levels of modification in vivo, and are still assembled into complexes. Taken together, these results suggest that ESC phosphorylation normally occurs after assembly into ESC-E(Z) complexes and that it contributes to the function or regulation of these complexes. We discuss how biochemically separable ESC-E(Z) and PC-PH complexes might work together to provide PcG repression.
AB - The extra sex combs (ESC) and Enhancer of zeste [E(Z)] proteins, members of the Polycomb group (PcG) of transcriptional repressors, interact directly and are coassociated in fly embryos. We report that these two proteins are components of a 600-kDa complex in embryos. Using gel filtration and affinity chromatography, we show that this complex is biochemically distinct from previously described complexes containing the PcG proteins Polyhomeotic, Polycomb, and Sex comb on midleg. In addition, we present evidence that ESC is phosphorylated in vivo and that this modified ESC is preferentially associated in the complex with E(Z). Modified ESC accumulates between 2 and 6 h of embryogenesis, which is the developmental time when esc function is first required. We find that mutations in E(z) reduce the ratio of modified to unmodified ESC in vivo. We have also generated germ line transformants that express ESC proteins bearing site-directed mutations that disrupt ESC- E(Z) binding in vitro. These mutant ESC proteins fail to provide esc function, show reduced levels of modification in vivo, and are still assembled into complexes. Taken together, these results suggest that ESC phosphorylation normally occurs after assembly into ESC-E(Z) complexes and that it contributes to the function or regulation of these complexes. We discuss how biochemically separable ESC-E(Z) and PC-PH complexes might work together to provide PcG repression.
UR - http://www.scopus.com/inward/record.url?scp=0033999219&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033999219&partnerID=8YFLogxK
U2 - 10.1128/MCB.20.9.3069-3078.2000
DO - 10.1128/MCB.20.9.3069-3078.2000
M3 - Article
C2 - 10757791
AN - SCOPUS:0033999219
SN - 0270-7306
VL - 20
SP - 3069
EP - 3078
JO - Molecular and cellular biology
JF - Molecular and cellular biology
IS - 9
ER -