Estrella LA, Wilkinson MF, González CI
The Shuttling Protein Npl3 Promotes Translation Termination Accuracy in Saccharomyces cerevisiae. [JOURNAL ARTICLE]
J Mol Biol 2009 Sep 2.
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are multi-functional proteins that bind to newly synthesized mRNAs in the nucleus and participate in many subsequent steps of gene expression. A well-studied Saccharomyces cerevisiae hnRNP that has several nuclear functions is Npl3p. Here, we provide evidence that Npl3p also has a cytoplasmic role: it functions in translation termination fidelity. Yeast harboring the npl3-95 mutant allele have impaired ability to translate LacZ, enhanced sensitivity to cycloheximide and paromomycin, and increased ability to readthrough translation termination codons. Most of these defects are enhanced in yeast that also lack Upf1p, a factor crucial for the nonsense-mediated decay (NMD) RNA surveillance pathway that is also known to be involved in translation termination. We show that the npl3-95 mutant allele encodes an Npl3p that forms high molecular-weight complexes that co-fractionate with the poly(A)-binding protein Pab1p. Together, the data suggest that Npl3p plays a role in translation termination in yeast.
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