July 2005
Heterochromatin assembly in S. pombe
Dr. Craig Peterson and colleagues have identified an S. pombe ubiquitin ligase that is required for heterochromatin formation and gene silencing. The authors purified the heterochromatin assembly protein, Rik1, along with two novel Rik-1 associated proteins that proved essential for H3-K9 methylation and centromere silencing. Intruigingly, they also found a novel Rik1-associated E3 ligase that is necessary for heterochromatin assembly.
"These data identify a cullin-dependent E3 ligase as a key component of a Clr4 methyltransferase complex, thus implying that polyubiquitylation of one or more regulatory proteins and their subsequent proteasome-dependent degradation may control histone methylation and heterochromatin formation," explains Dr. Peterson.