A role for the Drosophila SU(VAR)3-9 protein in chromatin organization at the histone gene cluster and in suppression of position-effect variegation.
Mutations in the gene for Su(var)3-9 are dominant suppressors of position-effect variegation (PEV). We show that SU(VAR)3-9 is a chromatin-associated protein and identify the large multicopy histone gene cluster (HIS-C) as one of its target loci. The organization of nucleosomes over the entire HIS-C region is altered in Su(var)3-9 mutants and there is a concomitant increase in expression of the histone genes. SU(VAR)3-9 is a histone H3 methyltransferase and, using chromatin immunoprecipitation, we show that SU(VAR)3-9 is present at the HIS-C locus and that the histone H3 at the HIS-C locus is methylated. We propose that SU(VAR)3-9 is involved in packaging HIS-C into a distinct chromatin domain that has some of the characteristics of beta-heterochromatin. We suggest that methylation of histone H3 is important for the chromatin structure at HIS-C. The chromosomal deficiency for the HIS-C is also a suppressor of PEV. In contrast to what might be expected, we show that hemizygosity for the HIS-C locus leads to a substantial increase in the histone transcripts.
Ner
Sarbjit S
SS
Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada. ner@zoology.ubc.ca
Harrington
Michael J
MJ
Grigliatti
Thomas A
TA
D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000235:genetics*; D004247:DNA / Q000235:genetics; D004330:Drosophila / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000235:genetics*; D008297:Male; D008780:Methyltransferases / Q000235:genetics*; D005810:Multigene Family; D009154:Mutation; D011496:Protein Methyltransferases; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics*; D013489:Suppression, Genetic
D002843:Chromatin; D029721:Drosophila Proteins; D006657:Histones; D012333:RNA, Messenger; D012097:Repressor Proteins; C089148:Su(var)3-9 protein, Drosophila; D004247:DNA; D000076983:Histone Methyltransferases; D008780:Methyltransferases; D011496:Protein Methyltransferases; C445404:SU(VAR)3-9; D011495:Histone-Lysine N-Methyltransferase