The Nuclear Poly(A)-Binding Protein Interacts with the Exosome to Promote Synthesis of Noncoding Small Nucleolar RNAs

SummaryPoly(A)-binding proteins (PABPs) are important to eukaryotic gene expression. In the nucleus, the PABP PABPN1 is thought to function in polyadenylation of pre-mRNAs. Deletion of fission yeast pab2, the homolog of mammalian PABPN1, results in transcripts with markedly longer poly(A) tails, but the nature of the hyperadenylated transcripts and the mechanism that leads to RNA hyperadenylation remain unclear. Here we report that Pab2 functions in the synthesis of noncoding RNAs, contrary to the notion that PABPs function exclusively on protein-coding mRNAs. Accordingly, the absence of Pab2 leads to the accumulation of polyadenylated small nucleolar RNAs (snoRNAs). Our findings suggest that Pab2 promotes poly(A) tail trimming from pre-snoRNAs by recruiting the nuclear exosome. This work unveils a function for the nuclear PABP in snoRNA synthesis and provides insights into exosome recruitment to polyadenylated RNAs.

Graphical AbstractFigure optionsDownload high-quality image (240 K)Download as PowerPoint slideHighlights
► Pab2 is not essential for mRNA synthesis
► Pab2 functions in noncoding snoRNA processing
► The nuclear exosome physically and functionally associates with Pab2
► Pab2 functions in a processing pathway with Rrp6, but distinct to the core exosome