SUV39: The Su(var)3-9 gene was originally identified in a genetic screen as a suppressor of position effect variegation in Drosophila. This was the first hint that the Su(var)3-9 protein might be involved in regulating chromatin structure. In mice, there are two highly related homologues of the Drosophila Su(var)3-9, Suv39h1 and Suv39h2. Following the identification of Suv39h1 as a lysine methyltransferase capable of methylating Lys9 of histone H3 (H3K9), confirmation that this protein can modulate chromatin architecture came with the finding that it creates a specific binding site for the heterochromatin protein HP1. As Suv39h1 and HP1 interact, it is thought that Suv39h1 methylating H3 K9, and then HP1 binding to the methylated H3, forms a positive feedback loop allowing HP1 and H3 K9 methylation to spread along chromatin, generating repressive heterochromatin in the process. (1)

Reference
1. Schneider R, Bannister AJ, Kouzarides T.Unsafe SETs: histone lysine methyltransferases and cancer. Trends Biochem Sci.2002;27(8):396-402. PMID: 12151224.