The Sir proteins can silence transcription in yeast at a number of loci, including the mating-type locus, telomeres, and rDNA genes. In an Advanced Online Publication in
In a screen for genes affecting silencing loci, Ray et al. identified the Slt2p enzyme as a kinase that phosphorylates Sir3p. Sir3p phosphorylation led to silencing control and reduced lifespan. Conversely, mutation of serine residues in Sir3p extended yeast lifespan by upto 38%. The affects on lifespan occurred independently from changes in rDNA recombination.