PR-Set7 Is a Nucleosome-Specific Methyltransferase that Modifies Lysine 20 of Histone H4 and Is Associated with Silent Chromatin

Abstract

We have purified a human histone H4 lysine 20 methyltransferase and cloned the encoding gene, PR/SET07. A mutation in Drosophila pr-set7 is lethal: second instar larval death coincides with the loss of H4 lysine 20 methylation, indicating a fundamental role for PR-Set7 in development. Transcriptionally competent regions lack H4 lysine 20 methylation, but the modification coincided with condensed chromosomal regions on polytene chromosomes, including chromocenter and euchromatic arms. The Drosophila male X chromosome, which is hyperacetylated at H4 lysine 16, has significantly decreased levels of lysine 20 methylation compared to that of females. In vitro, methylation of lysine 20 and acetylation of lysine 16 on the H4 tail are competitive. Taken together, these results support the hypothesis that methylation of H4 lysine 20 maintains silent chromatin, in part, by precluding neighboring acetylation on the H4 tail.

Histone H4 lysine 20 monomethylation promotes transcriptional repression by L3MBTL1

“…Initial reports highlighted the importance of H4K20me1 in 'facultative' heterochromatin and Xinactivation (Fang et al, 2002;Nishioka et al, 2002;Kohlmaier et al, 2004;Karachentsev et al, 2005;Martens et al, 2005;Sims et al, 2006). Recently, this exclusivity has been questioned by studies that suggest a role in transcriptional competence and elongation (Talasz et al, 2005;Vakoc et al, 2006;Barski et al, 2007;Pesavento et al, 2008).…”

“…Therefore, we investigated whether L3MBTL1 interacts with PR-SET7, the only known H4K20 monomethyltransferase (Fang et al, 2002;Nishioka et al, 2002). We transiently overexpressed HA-tagged L3MBTL1 and myc-tagged PR-SET7 in 293T cells.…”

Catalytic Function of the PR-Set7 Histone H4 Lysine 20 Monomethyltransferase Is Essential for Mitotic Entry and Genomic Stability

“…Whole cell lysates were collected 6 days post-transfection for Western analysis. A pQCXIP vectors (Clontech) containing either enhanced GFP or the full-length PR-Set7 R265G dominant negative mutant were transfected into HCT116 and HEK 293 cells using Lipofectamine 2000 (24). The samples were collected 3 days following puromycin selection for Western analysis and flow cytometry.…”

“…Trimethylated H4K20 is associated with repressed chromatin because it is targeted to constitutive heterochromatin, various repetitive elements, and imprinting control regions (16,18,19). Dimethylated H4K40 is more widely distributed within euchromatic regions in the genome, and recent findings suggest that it may function to recruit the 53BP1 repair protein to sites of DNA damage (17,20,21).The PR-Set7 enzyme is responsible for the bulk of H4K20 monomethylation (22)(23)(24)(25). Although original observations suggested that this modification was associated with repressed regions of the genome, recent findings have identified monomethylated H4K20 within actively transcribed genes (26,27).…”

“…The PR-Set7 enzyme is responsible for the bulk of H4K20 monomethylation (22)(23)(24)(25). Although original observations suggested that this modification was associated with repressed regions of the genome, recent findings have identified monomethylated H4K20 within actively transcribed genes (26,27).…”