Genome-wide study of nuclear poly(A) binding protein Nab2p depletion

Polyadenylation of mRNA is a key step in eu- karyotic gene expression. However, despite the ma- jor impact of poly(A) tails on mRNA metabolism, the precise roles of poly(A)-binding proteins (PABPs) in nuclear mRNA biogenesis remain elusive. Here, we demonstrate that rapid nuclear depletion of the S. cerevisiae PABP Nab2p leads to a global loss of cellular mRNA, but not of RNA lacking poly(A) tails. Disappearance of mRNA is a nuclear event, but not due to decreased transcription. Instead, the absence of Nab2p results in robust nuclear mRNA decay by the ribonucleolytic RNA exosome in a polyadenylation-dependent process. We con- clude that Nab2p is required to protect early mRNA and therefore constitutes a crucial nuclear mRNA biogenesis factor. Overall design: For RNAseq experiments, 2 independent biological replicates of Nab2-AA cells (Y3284) without rapamycin, or treated for 15’ or 30’, as well as control cells (Y2615) treated with rapamycin for 30’ were used. S. Pombe spike-in were used to normalize across samples.

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Schmid M, Olszewski P, Pelechano V, Gupta I, Steinmetz LM, Jensen TH