The ribotoxic stress response drives UV-mediated cell death.

While ultraviolet (UV) radiation damages DNA, eliciting the DNA damage response (DDR), it also damages RNA, triggering transcriptome-wide ribosomal collisions and eliciting a ribotoxic stress response (RSR). However, the relative contributions, timing, and regulation of these pathways in determining cell fate is unclear. Here we use time-resolved phosphoproteomic, chemical-genetic, single-cell imaging, and biochemical approaches to create a chronological atlas of signaling events activated in cells responding to UV damage. We discover that UV-induced apoptosis is mediated by the RSR kinase ZAK and not through the DDR. We identify two negative-feedback modules that regulate ZAK-mediated apoptosis: (1) GCN2 activation limits ribosomal collisions and attenuates ZAK-mediated RSR and (2) ZAK activity leads to phosphodegron autophosphorylation and its subsequent degradation. These events tune ZAK's activity to collision levels to establish regimes of homeostasis, tolerance, and death, revealing its key role as the cellular sentinel for nucleic acid damage.

B. subtilis MutS2 splits stalled ribosomes into subunits without mRNA cleavage.

Stalled ribosomes are rescued by pathways that recycle the ribosome and target the nascent polypeptide for degradation. In E. coli, these pathways are triggered by ribosome collisions through the recruitment of SmrB, a nuclease that cleaves the mRNA. In B. subtilis, the related protein MutS2 was recently implicated in ribosome rescue. Here we show that MutS2 is recruited to collisions by its SMR and KOW domains, and we reveal the interaction of these domains with collided ribosomes by cryo-EM. Using a combination of in vivo and in vitro approaches, we show that MutS2 uses its ABC ATPase activity to split ribosomes, targeting the nascent peptide for degradation through the ribosome quality control pathway. However, unlike SmrB, which cleaves mRNA in E. coli, we see no evidence that MutS2 mediates mRNA cleavage or promotes ribosome rescue by tmRNA. These findings clarify the biochemical and cellular roles of MutS2 in ribosome rescue in B. subtilis and raise questions about how these pathways function differently in diverse bacteria.

The Effects of Australia's First Residential Peer-Support Suicide Prevention and Recovery Centre (SPARC).

Aim: This paper reports preliminary evidence of the impacts of Australia's first residential peer-support service for people at risk of suicide. Methods: Psychological distress was measured preintervention, postintervention, and after 3 months and analyzed using paired t tests. Interviews were held postintervention and were analyzed using thematic analysis. Results: Psychological distress significantly improved from preintervention to postintervention (n = 16, d = 1.77) and at follow-up (n = 5, d = 1.12). Interviews (n = 10) indicated that participants experienced improvements in mental well-being and feelings of connectedness, respite, and confidence to engage with other services. The peer-support workers were key. Some participants felt that the location was too remote, too little information was given, and a longer stay would have been preferable. Limitations: The study did not include a control group, the sample was relatively small, and participants may have been subject to socially desirable answers. Conclusions: These findings indicate that residential peer-support services potentially offer a valuable alternative to conventional inpatient treatment for people at risk of suicide.

Genetic screens in Saccharomyces cerevisiae identify a role for 40S ribosome recycling factors Tma20 and Tma22 in nonsense-mediated decay.

The decay of messenger RNA with a premature termination codon by nonsense-mediated decay (NMD) is an important regulatory pathway for eukaryotes and an essential pathway in mammals. NMD is typically triggered by the ribosome terminating at a stop codon that is aberrantly distant from the poly-A tail. Here, we use a fluorescence screen to identify factors involved in NMD in Saccharomyces cerevisiae. In addition to the known NMD factors, including the entire UPF family (UPF1, UPF2, and UPF3), as well as NMD4 and EBS1, we identify factors known to function in posttermination recycling and characterize their contribution to NMD. These observations in S. cerevisiae expand on data in mammals indicating that the 60S recycling factor ABCE1 is important for NMD by showing that perturbations in factors implicated in 40S recycling also correlate with a loss of NMD.