Drosophila SETDB1 Is Required for Chromosome 4 Silencing

Abstract

Histone H3 lysine 9 (H3K9) methylation is associated with gene repression and heterochromatin formation. In Drosophila, SU(VAR)3–9 is responsible for H3K9 methylation mainly at pericentric heterochromatin. However, the histone methyltransferases responsible for H3K9 methylation at euchromatic sites, telomeres, and at the peculiar Chromosome 4 have not yet been identified. Here, we show that DmSETDB1 is involved in nonpericentric H3K9 methylation. Analysis of two DmSetdb1 alleles generated by homologous recombination, a deletion, and an allele where the 3HA tag is fused to the endogenous DmSetdb1, reveals that this gene is essential for fly viability and that DmSETDB1 localizes mainly at Chromosome 4. It also shows that DmSETDB1 is responsible for some of the H3K9 mono- and dimethyl marks in euchromatin and for H3K9 dimethylation on Chromosome 4. Moreover, DmSETDB1 is required for variegated repression of transgenes inserted on Chromosome 4. This study defines DmSETDB1 as a H3K9 methyltransferase that specifically targets euchromatin and the autosomal Chromosome 4 and shows that it is an essential factor for Chromosome 4 silencing.

Coordinated Regulation of Heterochromatic Genes inDrosophila melanogasterMales

“…All heterochromatic regions are marked by H3K9me, which creates a binding site for HP1. While Su(var)3-9 is responsible for the majority of H3K9me deposition throughout the rest of the genome, the dSETDB1 methyltransferase localizes to the fourth chromosome and is responsible for H3K9me accumulation there (Seum et al 2007;Tzeng et al 2007). Knock down of ISWI in S2 cells leads to a modest decrease in expression of fourth-linked genes (Bonaldi et al 2008).…”

DrosophilaCAF-1 regulates HP1-mediated epigenetic silencing and pericentric heterochromatin stability

“…In addition to HP1, the H3K9 monomethylation level of the polytene chromosomes is also affected by alterations of CAF-1 p180 gene expression (Fig. 3), effects that are similar to those caused by Drosophila Setdb1 gene expression alterations (Seum et al, 2007). Therefore, CAF-1 p180 probably interacts with not only HP1 but also other epigenetic factors, such as Drosophila SETDB1, to accomplish its functions in the process of heterochromatinization (Sarraf and Stancheva, 2004).…”

Identification of Nuclear Localization Signals of Drosophila G9a Histone H3 Methyltransferase

“…dG9a appears to have H3-K9 methyltransferase activity both in vitro and in vivo, and functions as a dominant suppressor of position effect of variegation (Mis et al, 2006). Although a reduced reproductivity of dG9a mutant flies suggests the involvement of dG9a in germ cell development (Mis et al, 2006;Lee et al, 2010), the other study indicates that dG9a is not essential for fly viability and reproduction (Seum et al, 2007). Furthermore, dG9a associates with Drosophila Atrophin which is a nuclear receptor co-repressor and is thought to be recruited to target gene promoters to repress their transcription (Mang et al, 2008).…”

“…Furthermore, other two HMTases in Drosophila have been identified. One of them, dSETDB1 is required for gene silencing of the fourth chromosome (Seum et al, 2007;Tzeng et al, 2007;Brower-Toland et al, 2009) and is critical during development (Seum et al, 2007;Tzeng et al, 2007). Another HMTase, Drosophila G9a (dG9a) appears to be a functional homologue of human G9a and GLP/Eu-HMTase1 (Mis et al, 2006;Stabell et al, 2006).…”