Alternative ESC and ESC-like subunits of a polycomb group histone methyltransferase complex are differentially deployed during Drosophila development.
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.
Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275, USA.
Liangjun
L
Wang
Neal
N
Jahren
Marcus L
ML
Vargas
Erica F
EF
Andersen
Judith
J
Benes
Junyu
J
Zhang
Ellen L
EL
Miller
Richard S
RS
Jones
Jeffrey A
JA
Simon
D000595:Amino Acid Sequence; D000818:Animals; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000166:cytology / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D024861:Genetic Enhancement; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D063150:Polycomb Repressive Complex 1; D063151:Polycomb Repressive Complex 2; D011485:Protein Binding; D011496:Protein Methyltransferases; D021122:Protein Subunits / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014921:Wings, Animal / Q000378:metabolism
D002843:Chromatin; D029721:Drosophila Proteins; C530980:ESCL protein, Drosophila; D018398:Homeodomain Proteins; C066770:Pc protein, Drosophila; D021122:Protein Subunits; D012097:Repressor Proteins; C543390:Su(z)12 protein, Drosophila; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D063151:Polycomb Repressive Complex 2; C543389:esc protein, Drosophila; D063150:Polycomb Repressive Complex 1