Project description:RNA-DNA hybrids form throughout the chromosome during normal cell growth and under stress conditions. When left unresolved, RNA-DNA hybrids can slow replication fork progression, cause DNA breaks, increase mutagenesis, and reduce gene expression. To remove hybrids, all organisms use ribonuclease H (RNase H) to specifically degrade the RNA portion of RNA-DNA hybrids. Here we show that, in addition to chromosomally encoded RNase HII and RNase HIII, Bacillus subtilis NCIB 3610 encodes a previously uncharacterized RNase HI protein, RnhP, on the endogenous plasmid pBS32. Like other RNase HI enzymes, RnhP incises Okazaki fragments, ribopatches, and a complementary RNA-DNA hybrid. We show that while chromosomally encoded RNase HIII is required for pBS32 hyper-replication, RnhP compensates for loss of RNase HIII activity on the chromosome. Consequently, loss of RnhP and RNase HIII impairs bacterial growth. We show that the decreased growth rate can be explained by laggard replication fork progression near the terminus region of the right replichore resulting in SOS-dependent inhibition of cell division. We conclude that B. subtilis NCIB 3610 encodes functional RNase HI, HII, and HIII, and pBS32-encoded RNase HI contributes to replication fork progression and chromosome stability while RNase HIII is important for chromosome stability and plasmid hyper-replication.
Project description:RNA-DNA hybrids form throughout the chromosome during normal cell growth and under stress conditions. When left unresolved, RNA-DNA hybrids can slow replication fork progression, cause DNA breaks, increase mutagenesis, and reduce gene expression. To remove hybrids, all organisms use ribonuclease H (RNase H) to specifically degrade the RNA portion of RNA-DNA hybrids. Here we show that, in addition to chromosomally encoded RNase HII and RNase HIII, Bacillus subtilis NCIB 3610 encodes a previously uncharacterized RNase HI protein, RnhP, on the endogenous plasmid pBS32. Like other RNase HI enzymes, RnhP incises Okazaki fragments, ribopatches, and a complementary RNA-DNA hybrid. We show that while chromosomally encoded RNase HIII is required for pBS32 hyper-replication, RnhP compensates for loss of RNase HIII activity on the chromosome. Consequently, loss of RnhP and RNase HIII impairs bacterial growth. We show that the decreased growth rate can be explained by laggard replication fork progression near the terminus region of the right replichore resulting in SOS-dependent inhibition of cell division. We conclude that B. subtilis NCIB 3610 encodes functional RNase HI, HII, and HIII, and pBS32-encoded RNase HI contributes to replication fork progression and chromosome stability while RNase HIII is important for chromosome stability and plasmid hyper-replication.
Project description:RNase J1 is the first nuclease with 5-3 exonuclease activity in bacteria and plays an important role in the maturation and degradation of mRNA. Absence of RNase J1 in cells has effect on cell morphology and growth rate. We did RNA-seq of Bacillus subtilis wild type and RNase J1 null strains (triplicates) to obtain more information about cellular role of this nuclease in cells. Complmentary ChIP-seq data have also been deposited in ArrayExpress under accession number E-MTAB-5659 ( https://www.ebi.ac.uk/arrayexpress/experiments/E-MTAB-5659 ).
Project description:RNase Y and RNase E are disparate endoribonucleases that govern global mRNA turnover/processing in the two evolutionary distant bacteria Bacillus subtilis and Escherichia coli, respectively. The two enzymes share a similar in vitro cleavage specificity and subcellular localization. To evaluate the potential equivalence in biological function between the two enzymes in vivo we analyzed whether and to what extent RNase E is able to replace RNase Y in B. subtilis. Full-length RNase E almost completely restores wild type growth of the rny mutant. This is matched by a surprising reversal of transcript profiles both of individual genes and on a genome-wide scale. The single most important parameter to efficient complementation is the requirement for RNase E to localize to the inner membrane while truncation of the C-terminal sequences corresponding to the degradosome scaffold has only a minor effect. We also compared the in vitro cleavage activity for the major decay initiating ribonucleases Y, E and J and show that no conclusions can be drawn with respect to their activity in vivo. Our data confirm the notion that RNase Y and RNase E have evolved through convergent evolution towards a low specificity endonuclease activity universally important in bacteria.
Project description:RNA-DNA hybrids are common in chromosomal DNA. Persistent RNA-DNA hybrids result in replication fork stress, DNA breaks, and neurological disorders in humans. During replication, Okazaki fragment synthesis relies on frequent RNA primer placement, providing one of the most prominent forms of covalent RNA-DNA strands in vivo The mechanism of Okazaki fragment maturation, which involves RNA removal and subsequent DNA replacement, in bacteria lacking RNase HI remains unclear. In this work, we reconstituted repair of a linear model Okazaki fragment in vitro using purified recombinant enzymes from Bacillus subtilis We showed that RNase HII and HIII are capable of incision on Okazaki fragments in vitro and that both enzymes show mild stimulation by single-stranded DNA binding protein (SSB). We also showed that RNase HIII and DNA polymerase I provide the primary pathway for Okazaki fragment maturation in vitro Furthermore, we found that YpcP is a 5' to 3' nuclease that can act on a wide variety of RNA- and DNA-containing substrates and exhibits preference for degrading RNA in model Okazaki fragments. Together, our data showed that RNase HIII and DNA polymerase I provide the primary pathway for Okazaki fragment maturation, whereas YpcP also contributes to the removal of RNA from an Okazaki fragment in vitroIMPORTANCE All cells are required to resolve the different types of RNA-DNA hybrids that form in vivo When RNA-DNA hybrids persist, cells experience an increase in mutation rate and problems with DNA replication. Okazaki fragment synthesis on the lagging strand requires an RNA primer to begin synthesis of each fragment. The mechanism of RNA removal from Okazaki fragments remains unknown in bacteria that lack RNase HI. We examined Okazaki fragment processing in vitro and found that RNase HIII in conjunction with DNA polymerase I represent the most efficient repair pathway. We also assessed the contribution of YpcP and found that YpcP is a 5' to 3' exonuclease that prefers RNA substrates with activity on Okazaki and flap substrates in vitro.
Project description:RNase Y is a key endoribonuclease affecting global mRNA stability in Bacillus subtilis. Its characterization provided the first evidence that endonucleolytic cleavage plays a major role in the mRNA metabolism of this organism. RNase Y shares important functional features with the RNA decay initiating RNase E from Escherichia coli, notably a similar cleavage specificity and a preference for 5' monophosphorylated substrates. We used high-resolution tiling arrays to analyze the effect of RNase Y depletion on RNA abundance covering the entire genome. The data confirm that this endoribonuclease plays a key role in initiating the decay of a large number of mRNAs as well as non coding RNAs. The downstream cleavage products are likely to be degraded by the 5' exonucleolytic activity of RNases J1/J2 as we show for a specific case. Comparison of the data with that of two other recent studies revealed very significant differences. About two thirds of the mRNAs upregulated following RNase Y depletion were different when compared to either one of these studies and only about 10% were in common in all three studies. This highlights that experimental conditions and data analysis play an important role in identifying RNase Y substrates by global transcriptional profiling. Our data confirmed already known RNase Y substrates and due to the precision and reproducibility of the profiles allow an exceptionally detailed view of the turnover of hundreds of new RNA substrates.
Project description:In contrast to Escherichia coli, initiation of mRNA decay in Gram-positive organisms is poorly understood. We studied the fate of the highly structured RNAs generated by premature transcription termination of S-adenosylmethionine (SAM)-dependent riboswitches in Bacillus subtilis. An essential protein of earlier unknown function, YmdA, was identified as a novel endoribonuclease (now called RNase Y) that was capable of preferential cleaving in vitro of the 5' monophosphorylated yitJ riboswitch upstream of the SAM-binding aptamer domain. Antiterminated full-length yitJ mRNA was not a substrate for RNase Y in vivo and in vitro, transcripts capable of forming the antiterminator were only cleaved in the presence of SAM. Turnover of 10 other SAM-dependent riboswitches was also initiated by RNase Y. Depletion of this ribonuclease increased the half-life of bulk mRNA more than two-fold. This indicates that RNase Y might be not only important for riboswitch RNA turnover but also as a key player in the initiation of mRNA decay in B. subtilis. About 40% of the sequenced eubacterial species have an RNase Y orthologue.