Rrp6p

Rrp6p is a nuclear 3' to 5' exoribonuclease in the yeast Saccharomyces cerevisiae. It serves as the nuclear exosome-associated catalytic subunit and is encoded by the RRP6 gene. Rrp6p is the yeast homolog of the human EXOSC10 (PM/Scl-100) component and is a key part of the exosome complex operating in the nucleus.

Function and role: Rrp6p participates in RNA processing and surveillance within the nucleus. It contributes to the maturation of various RNA species, including ribosomal RNA precursors and small nucleolar RNAs, and it is involved in the degradation and quality control of aberrant transcripts. Rrp6p often works in conjunction with the core exosome and nuclear cofactors to trim RNA 3' ends and remove defective or unnecessary RNAs, including cryptic unstable transcripts generated by pervasive transcription.

Localization and interactions: Rrp6p is predominantly localized to the nucleus, where it associates with the exosome core to form the holo-exosome. Its activity is enhanced by cofactors such as Rrp47, which stabilizes Rrp6p and stimulates its exonuclease activity. Additional factors, and the core exosome itself, help channel substrates to Rrp6p for processing or degradation.

Genetic and functional significance: Loss or impairment of RRP6 leads to accumulation of unprocessed or misprocessed RNA species, defects in rRNA and snoRNA maturation, and increased levels of unstable nuclear RNAs. Mutations or deletions can cause growth defects and show synthetic interactions with other exosome or TRAMP complex components, underscoring Rrp6p’s role in nuclear RNA metabolism.

Evolution and overview: Rrp6p is evolutionarily conserved as EXOSC10 homologs across eukaryotes, reflecting its fundamental role in nuclear RNA processing and surveillance.