DNA interstrand crosslink (ICL) repair requires a complex network of DNA damage response pathways. Removal of the ICL lesions is vital, as they are physical barriers to essential DNA processes that require the separation of duplex DNA, such as replication and transcription. The Fanconi anemia (FA) pathway is the principal mechanism for ICL repair in metazoans and is coupled to DNA replication. In Saccharomyces cerevisiae, a vestigial FA pathway is present, but ICLs are predominantly repaired by a pathway involving the Pso2 nuclease, which is hypothesized to use its exonuclease activity to digest through the lesion to provide access for translesion polymerases. However, Pso2 lacks translesion nuclease activity in vitro, and mechanistic details of this pathway are lacking, especially relative to FA. We recently identified the Hrq1 helicase, a homolog of the disease-linked enzyme RecQ-like helicase 4 (RECQL4), as a component of Pso2-mediated ICL repair. Here, using genetic, biochemical, and biophysical approaches, including single-molecule FRET (smFRET)– and gel-based nuclease assays, we show that Hrq1 stimulates the Pso2 nuclease through a mechanism that requires Hrq1 catalytic activity. Importantly, Hrq1 also stimulated Pso2 translesion nuclease activity through a site-specific ICL in vitro. We noted that stimulation of Pso2 nuclease activity is specific to eukaryotic RecQ4 subfamily helicases, and genetic and biochemical data suggest that Hrq1 likely interacts with Pso2 through their N-terminal domains. These results advance our understanding of FA-independent ICL repair and establish a role for the RecQ4 helicases in the repair of these detrimental DNA lesions.

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DNA inter-strand crosslink (ICL) repair requires a complicated network of DNA damage response pathways. Removal of these lesions is vital as they are physical barriers to essential DNA processes that require the separation of duplex DNA, such as replication and transcription. The Fanconi anemia (FA) pathway is the principle mechanism for ICL repair in metazoans and is coupled to replication (1).In Saccharomyces cerevisiae, a degenerate FA pathway is present, but ICLs are predominantly repaired by a pathway involving the Pso2 nuclease that is hypothesized to digest through the lesion to provide access for translesion polymerases (2). However, mechanistic details of this pathway are lacking, especially relative to FA. We recently identified the Hrq1 helicase, a homolog of the diseaselinked RECQL4, as a novel component of Pso2-mediated ICL repair (3). Here, we show that Hrq1 stimulates the Pso2 nuclease in a mechanism that requires Hrq1 catalytic activity. Importantly, Pso2 alone has meagre translesion nuclease activity on an ICL-containing substrate, but digestion through the lesion dramatically increases in the presence of Hrq1. Stimulation of Pso2 nuclease activity is specific to eukaryotic RecQ4 subfamily helicases, and Hrq1 interacts with Pso2, likely through their Ntermini. These results advance our understanding of FA-independent ICL repair and establish a role for the RecQ4 helicases in the repair of these dangerous lesions.

BackgroundWhile online reviews from physician rating websites are increasingly utilized by healthcare providers to better understand patient needs, it remains difficult to objectively identify areas for improvement in providing psychiatric care.ObjectivesTo quantitatively characterize the sentiment of online written reviews of psychiatrists to determine clinical attributes that can be strengthened to improve psychiatrists’ therapeutic alliance with their patients.Materials and methodsSentiment scores of 6,400 written reviews of 400 US-based psychiatrists on a US-based online physician rating website were obtained through a natural-language-processing-based sentiment analysis. Relationships among sentiment scores, average star ratings, and demographics were examined. Linguistic analyses determined words and bigrams that were highly associated with reviews with the most positive and negative sentiment.FindingsSentiment scores were significantly correlated with average star ratings of the psychiatrists (R = 0.737, p < 0.001). Psychiatrists who were younger (< 56 years old) and/or practiced in the Northeast had significantly higher average star ratings than those older and/or practicing in the Southwest. Frequency analysis showed that positive reviews most frequently contained “time” (N = 1,138) and “caring” (N = 784) while negative reviews most frequently contained “medication” (N = 495) and “time” (N = 379). Logistic regression analysis revealed that reviews were more likely to be considered positive when they included “great listener” (OR = 16.89) and “comfortable” (OR = 10.72) and more likely to be negative when they included “meds” (OR = 0.55) and “side effect” (OR = 0.59).ConclusionPsychiatrists who are younger and located in the Northeast receive more positive reviews; there may be potential for demographic bias among patient reviewers. Patients positively rate psychiatrists who make them feel heard and comfortable but negatively rate encounters centered around medications and their side effects. Our study lends quantitative evidence to support the importance of thorough and empathetic communication of psychiatrists in building a strong therapeutic alliance.