Viral Factors Reveal a Role for REF/Aly in Nuclear RNA Stability

Abstract

TREX is a conserved multiprotein complex that is necessary for efficient mRNA export to the cytoplasm. In Saccharomyces cerevisiae, the TREX complex is additionally implicated in RNA quality control pathways, but it is unclear whether this function is conserved in mammalian cells. The Kaposi's sarcoma-associated herpesvirus (KSHV) ORF57 protein binds and recruits the TREX component REF/Aly to viral mRNAs. Here, we demonstrate that REF/Aly is recruited to the KSHV noncoding polyadenylated nuclear (PAN) RNA by ORF57. This recruitment correlates with ORF57-mediated stabilization of PAN RNA, suggesting that REF/Aly promotes nuclear RNA stability. Further supporting this idea, tethering REF/Aly to PAN RNA is sufficient to increase the nuclear abundance and half-life of PAN RNA but is not sufficient to promote its export. Interestingly, REF/Aly appears to protect the poly(A) tail from deadenylation, and REF/Aly-stabilized transcripts are further adenylated over time, consistent with previous reports linking poly(A) tail length with nuclear RNA surveillance. These studies show that REF/Aly can stabilize nuclear RNAs independently of their export and support a broader conservation of RNA quality control mechanisms from yeast to humans.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.06420-11.

ACKNOWLEDGMENTS

We thank Julie Pfeiffer and Ivan D'Orso for critical review of the manuscript. This work was funded by the NIH-NIAID grant AI081710 and by Welch Foundation research grant I-1732. N.K.C. is a Southwestern Medical Foundation Scholar in Biomedical Research. S.H.S. was supported by an NIH Molecular Microbiology training grant (5T32AI007520-12). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

S.H.S. performed experiments, wrote the paper, and designed experiments, O.V.H. and A.H. performed experiments, and N.K.C. designed experiments and wrote the paper.

We declare that we have no conflicts of interest.