Dual requirement for yeast hnRNP Nab2p in mRNA poly(A) tail length control and nuclear export

AUTOR(ES)

Hector, Ronald E.

FONTE

Oxford University Press

RESUMO

Recent studies of mRNA export factors have provided additional evidence for a mechanistic link between mRNA 3′-end formation and nuclear export. Here, we identify Nab2p as a nuclear poly(A)-binding protein required for both poly(A) tail length control and nuclear export of mRNA. Loss of NAB2 expression leads to hyperadenylation and nuclear accumulation of poly(A)+ RNA but, in contrast to mRNA export mutants, these defects can be uncoupled in a nab2 mutant strain. Previous studies have implicated the cytoplasmic poly(A) tail-binding protein Pab1p in poly(A) tail length control during polyadenylation. Although cells are viable in the absence of NAB2 expression when PAB1 is overexpressed, Pab1p fails to resolve the nab2Δ hyperadenylation defect even when Pab1p is tagged with a nuclear localization sequence and targeted to the nucleus. These results indicate that Nab2p is essential for poly(A) tail length control in vivo, and we demonstrate that Nab2p activates polyadenylation, while inhibiting hyperadenylation, in the absence of Pab1p in vitro. We propose that Nab2p provides an important link between the termination of mRNA polyadenylation and nuclear export.

Documentos Relacionados

• Distinct RNP Complexes of Shuttling hnRNP Proteins with Pre-mRNA and mRNA: Candidate Intermediates in Formation and Export of mRNA
• mRNA poly(A) tail, a 3' enhancer of translational initiation.
• Uncoupling of the hnRNP Npl3p from mRNAs during the stress-induced block in mRNA export
• mRNA with a <20-nt poly(A) tail imparted by the poly(A)-limiting element is translated as efficiently in vivo as long poly(A) mRNA
• A Nuclear 3′-5′ Exonuclease Involved in mRNA Degradation Interacts with Poly(A) Polymerase and the hnRNA Protein Npl3p