Proteasomes beyond proteolysis: Roles in heterochromatin maintenance.

In addition to its proteolytic roles, the 26S proteasome is involved in regulating transcription and in promoting sites of active chromatin. In this report, Seo et al. provide evidence that the non-proteolytic 19S subunit of the 26S proteasome also regulates the spreading of inactive chromatin referred to as heterochromatin, suggesting further non-canonical roles of the proteasome in gene expression.