A dimeric viral SET domain methyltransferase specific to Lys27 of histone H3

• DOI: 10.1038/nsb898
• Publication Date: 2003-02-25T18:41:24Z
• Authors: Karishma L. Manzur; Amjad Farooq; Lei Zeng; Olga Plotnikova; Alexander W. Koch; Sachchidanand; Ming-Ming Zhou
• Keywords: Histone Methylation; Histone octamer

Site-specific lysine methylation of histones by SET domains is a hallmark for epigenetic control of gene transcription in eukaryotic organisms. Here we report that a SET domain protein from Paramecium bursaria chlorella virus can specifically di-methylate Lys27 in histone H3, a modification implicated in gene silencing. The solution structure of the viral SET domain reveals a butterfly-shaped head-to-head symmetric dimer different from other known protein methyltransferases. Each subunit consists of a Greek-key antiparallel beta-barrel and a three-stranded open-faced sandwich that mediates the dimer interface. Cofactor S-adenosyl-L-methionine (SAM) binds at the opening of the beta-barrel, and amino acids C-terminal to Lys27 in H3 and in the flexible C-terminal tail of the enzyme confer the specificity of this viral histone methyltransferase.