{"title":"The bacterial transcription terminator, Rho, functions as an RNA:DNA hybrid (RDH) helicase in vivo.","authors":"Ankita Bhosale,Ranjan Sen","doi":"10.1042/bcj20253089","DOIUrl":null,"url":null,"abstract":"Ribonuclease HI (rnhA) removes the deleterious RNA:DNA hybrids (RDHs) by cleaving its RNA component. The bacterial transcription terminator Rho is an RNA-dependent 5' → 3' helicase capable of unwinding RDH formed on a single-stranded RNA in vitro. We hypothesize that Rho might be directly involved in RDH removal in vivo. Here, we demonstrate that Rho primary RNA-binding site (PBS) mutants defective in RNA binding and helicase activity are synthetically lethal specifically when RNase HI is absent. This lethality was not observed in the absence of RNase HII (rnhB) alone. Rho-PBS mutants in an rnhA- strain exhibited increased plasmid-concatemer and plasmid copy number, altered cell morphology, and were highly susceptible to DNA-damaging agents. These Rho mutants increased the accumulation of RDHs in vivo, suggesting defects in the RDH removal process. Rho was colocalized to RDHs in vivo when RNase HI was absent. Certain catalytically inactive mutants of RNase H that bind to the RDH blocked the entry of Rho to the RDH, inducing cell death, indicating the role of Rho in the removal of deleterious RDHs in the absence of RNase HI. Under in vitro conditions, Rho was capable of binding to the RDHs and unwinding them in a rut-site-dependent manner. Therefore, we concluded that in the absence of RNase HI, Rho, by its RNA-dependent helicase activity, is capable of unwinding RDHs in a rut-site-dependent manner. These results establish the non-transcription terminator role of Rho and its functional synergy with RNase HI in vivo.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"16 1","pages":""},"PeriodicalIF":4.3000,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochemical Journal","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1042/bcj20253089","RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Ribonuclease HI (rnhA) removes the deleterious RNA:DNA hybrids (RDHs) by cleaving its RNA component. The bacterial transcription terminator Rho is an RNA-dependent 5' → 3' helicase capable of unwinding RDH formed on a single-stranded RNA in vitro. We hypothesize that Rho might be directly involved in RDH removal in vivo. Here, we demonstrate that Rho primary RNA-binding site (PBS) mutants defective in RNA binding and helicase activity are synthetically lethal specifically when RNase HI is absent. This lethality was not observed in the absence of RNase HII (rnhB) alone. Rho-PBS mutants in an rnhA- strain exhibited increased plasmid-concatemer and plasmid copy number, altered cell morphology, and were highly susceptible to DNA-damaging agents. These Rho mutants increased the accumulation of RDHs in vivo, suggesting defects in the RDH removal process. Rho was colocalized to RDHs in vivo when RNase HI was absent. Certain catalytically inactive mutants of RNase H that bind to the RDH blocked the entry of Rho to the RDH, inducing cell death, indicating the role of Rho in the removal of deleterious RDHs in the absence of RNase HI. Under in vitro conditions, Rho was capable of binding to the RDHs and unwinding them in a rut-site-dependent manner. Therefore, we concluded that in the absence of RNase HI, Rho, by its RNA-dependent helicase activity, is capable of unwinding RDHs in a rut-site-dependent manner. These results establish the non-transcription terminator role of Rho and its functional synergy with RNase HI in vivo.
期刊介绍:
Exploring the molecular mechanisms that underpin key biological processes, the Biochemical Journal is a leading bioscience journal publishing high-impact scientific research papers and reviews on the latest advances and new mechanistic concepts in the fields of biochemistry, cellular biosciences and molecular biology.
The Journal and its Editorial Board are committed to publishing work that provides a significant advance to current understanding or mechanistic insights; studies that go beyond observational work using in vitro and/or in vivo approaches are welcomed.
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