Proliferating cell nuclear antigen (PCNA) contributes to the high-order structure and stability of heterochromatin in Saccharomyces cerevisiae.

Heterochromatin plays important roles in the structure, maintenance, and function of the eukaryotic genome. It is associated with special histone modifications and specialized non-histone proteins and assumes a more compact structure than euchromatin. Genes embedded in heterochromatin are generally transcriptionally silent. It was found previously that several mutations of proliferating cell nuclear antigen (PCNA), a DNA replication processivity factor, reduce transcriptional silencing at heterochromatin loci in Saccharomyces cerevisiae. However, the notion that PCNA plays a role in transcriptional silencing was recently questioned because of a potential problem concerning the silencing assays used in prior studies. To determine if PCNA is a bona fide contributor to heterochromatin-mediated transcriptional silencing, we examined the effects of PCNA mutations on heterochromatin structure. We found evidence implicating PCNA in the maintenance of the high-order structure and stability of heterochromatin, which indicates a role of DNA replication in heterochromatin maintenance.