Palmitoylation controls the dynamics of budding-yeast heterochromatin via the telomere-binding protein Rif1

Abstract

The posttranslational addition of palmitate to cysteines occurs ubiquitously in eukaryotic cells, where it functions in anchoring target proteins to membranes and in vesicular trafficking. Here we show that the Saccharomyces cerevisiae palmitoyltransferase Pfa4 enhanced heterochromatin formation at the cryptic mating-type loci HMR and HML via Rif1, a telomere regulatory protein. Acylated Rif1 was detected in extracts from wild-type but not pfa4Δ mutant cells. In a pfa4Δ mutant, Rif1-GFP dispersed away from foci positioned at the nuclear periphery into the nucleoplasm. Sir3-GFP distribution was also perturbed, indicating a change in the nuclear dynamics of heterochromatin proteins. Genetic analyses indicated that PFA4 functioned upstream of RIF1. Surprisingly, the pfa4Δ mutation had only mild effects on telomeric regulation, suggesting Rif1's roles at HM loci and telomeres were more complexly related than previously thought. These data supported a model in which Pfa4-dependent palmitoylation of Rif1 anchored it to the inner nuclear membrane, influencing its role in heterochromatin dynamics.