Different nuclease requirements for exosome-mediated degradation of normal and nonstop mRNAs

Abstract

Two general pathways of mRNA decay have been characterized in yeast. In one pathway, the mRNA is degraded by the cytoplasmic form of the exosome. The exosome has both 3′ to 5′ exoribonuclease and endoribonuclease activity, and the available evidence suggests that the exonuclease activity is required for the degradation of mRNAs. We confirm here that this is true for normal mRNAs, but that aberrant mRNAs that lack a stop codon can be efficiently degraded in the absence of the exonuclease activity of the exosome. Specifically, we show that the endo-and exonuclease activities of the exosome are both capable of rapidly degrading nonstop mRNAs and ribozyme-cleaved mRNAs. Additionally, the endonuclease activity of the exosome is not required for endonucleolytic cleavage in no-go decay. In vitro, the endonuclease domain of the exosome is active only under nonphysiological conditions, but our findings show that the in vivo activity is sufficient for the rapid degradation of nonstop mRNAs. Thus, whereas normal mRNAs are degraded by two exonucleases (Xrn1p and Rrp44p), several endonucleases contribute to the decay of many aberrant mRNAs, including transcripts subject to nonstop and nogo decay. Our findings suggest that the nuclease requirements for general and nonstop mRNA decay are different, and describe a molecular function of the core exosome that is not disrupted by inactivating its exonuclease activity.Dis3 | Saccharomyces cerevisiae

The Hbs1-Dom34 Protein Complex Functions in Non-stop mRNA Decay in Mammalian Cells

“…In yeast, non-stop mRNA is degraded by Rrp44, which has both exonuclease and endonuclease activities conferred by the PIN domain in the N terminus and the RNase II/R domain in the C terminus (26,52,53). Human Dis3 is similar to yeast Rrp44 not only in terms of sequence conservation but also in possessing the two distinct ribonucleolytic activities.…”

Ribosome-Associated Complex and Ssb Are Required for Translational Repression Induced by Polylysine Segments within Nascent Chains

“…Because Ski7 recruits the exosome, the increase in the molecular mass of the nonstop protein was likely related to the status of the nonstop transcript. It was recently discovered that the endonuclease activity of the exosome plays an important role in NSD (49). Depending on where endonucleolytic cleavage of a nonstop transcript occurs, only slightly extended nonstop proteins might be generated.…”

Spatial Distribution of Cellular Function: The Partitioning of Proteins between Mitochondria and the Nucleus in MCF7 Breast Cancer Cells

“…53 For example, the RNase exosome complex, which exists in both the nucleus and the cytoplasm, is involved in many types of RNA processing associated with nuclear-transcribed proteins, including mRNA decay. 54,55 The nine core proteins of this complex were observed exclusively in the nuclear fraction (Supporting Information Table 3). For the 13 proteins that are transcribed inas TSFM, TACO1, SLIRP and PUS1, 53 which we observed exclusively in the mitochondrial fraction (Supporting Information Table 3).…”