CEP90

CEP90, or **Cytoplasmic Exosome Pathway Protein 90**, is a component of the cytoplasmic exosome, a multi-subunit complex involved in RNA degradation and processing in eukaryotic cells. The exosome plays a critical role in maintaining cellular RNA homeostasis by degrading aberrant transcripts, regulating gene expression, and influencing various cellular processes such as development, stress responses, and disease progression.

The cytoplasmic exosome is composed of nine core subunits, each with distinct but overlapping functions. CEP90, also known as **RRP40** in yeast or **EXOSC9** in humans, is one of these subunits. It belongs to the RNase PH family of proteins, characterized by a conserved RNase PH domain that contributes to the exosome’s exonuclease activity. This domain facilitates the hydrolysis of RNA from the 3’ end, ensuring proper RNA turnover.

Studies in model organisms, particularly yeast (*Saccharomyces cerevisiae*), have highlighted the importance of CEP90 in exosome assembly and function. Mutations or deletions of CEP90 lead to defects in RNA degradation, accumulation of unstable transcripts, and cellular stress responses. In humans, EXOSC9 mutations have been linked to neurological disorders, including microcephaly and intellectual disability, underscoring its broader physiological significance.

The cytoplasmic exosome, including CEP90, operates in concert with other factors such as the TRAMP complex (a polyadenylation and helicase complex) to target specific RNA substrates for degradation. This interplay ensures precise regulation of RNA levels, preventing the accumulation of harmful transcripts while allowing stable mRNAs to persist. Research into CEP90 continues to explore its potential roles in disease mechanisms and therapeutic targets, particularly in cancers and neurodegenerative conditions where RNA metabolism is often dysregulated.