SU(VAR)3-9 is a conserved key function in heterochromatic gene silencing.
This review summarizes genetic, molecular and biochemical studies of the SU(VAR)3-9 protein and the evidence for its key role in heterochromatin formation and heterochromatic gene silencing. The Su(var)3-9 locus was first identified as a dominant modifier of position-effect variegation (PEV) in Drosophila melanogaster. Together with Su(var)2-5 and Su(var)3-7, Su(var)3-9 belongs to the group of haplo-suppressor loci which show a triplo-dependent enhancer effect. All three genes encode heterochromatin-associated proteins. Su(var)3-9 is epistatic to the PEV modifier effects of Su(var)2-5 and Su(var)3-7, and it also dominates the effect of the Y chromosome on PEV. These genetic data support a central role of the SU(VAR)3-9 protein in heterochromatic gene silencing, one that is correlated with its activity as a histone H3-K9 methyltransferase (HMTase). In fact, SU(VAR)3-9 is the main chromocenter-specific HMTase of Drosophila. SU(VAR)3-9 and HP1, the product of Su(var)2-5, are main constituents of heterochromatin protein complexes and the interaction between these two proteins is interdependent. Functional analysis in fission yeast, Drosophila and mammals demonstrate that SU(VAR)3-9-dependent gene silencing processes are conserved in these organisms. This is also demonstrated by the rescue of Drosophila Su(var)3-9 mutant phenotypes with human SUV39H1 transgenes.
Schotta
Gunnar
G
Institut für Genetik, Biologicum, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, D-06120 Halle, Germany.
Ebert
Anja
A
Reuter
Gunter
G
D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics*; D019143:Evolution, Molecular; D020868:Gene Silencing; D006570:Heterochromatin / Q000235:genetics*; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D008780:Methyltransferases / Q000235:genetics*; D011496:Protein Methyltransferases
D006570:Heterochromatin; D000076983:Histone Methyltransferases; D008780:Methyltransferases; D011496:Protein Methyltransferases; C445404:SU(VAR)3-9; D011495:Histone-Lysine N-Methyltransferase