Transcriptional coupling of DNA repair in sporulating Bacillus subtilis cells

Abstract

SummaryIn conditions of halted or limited genome replication, like those experienced in sporulating cells of Bacillus subtilis, a more immediate detriment caused by DNA damage is altering the transcriptional programme that drives this developmental process. Here, we report that mfd, which encodes a conserved bacterial protein that mediates transcription-coupled DNA repair (TCR), is expressed together with uvrA in both compartments of B. subtilis sporangia. The function of Mfd was found to be important for processing the genetic damage during B. subtilis sporulation. Disruption of mfd sensitized developing spores to mitomycin-C (M-C) treatment and UV-C irradiation. Interestingly, in nongrowing sporulating cells, Mfd played an antimutagenic role as its absence promoted UV-induced mutagenesis through a pathway involving YqjH/YqjWmediated translesion synthesis (TLS). Two observations supported the participation of Mfd-dependent TCR in spore morphogenesis: (i) disruption of mfd notoriously affected the efficiency of B. subtilis sporulation and (ii) in comparison with the wild-type strain, a significant proportion of Mfd-deficient sporangia that survived UV-C treatment developed an asporogenous phenotype. We propose that the Mfd-dependent repair pathway operates during B. subtilis sporulation and that its function is required to eliminate genetic damage from transcriptionally active genes.

Aag Hypoxanthine-DNA Glycosylase Is Synthesized in the Forespore Compartment and Involved in Counteracting the Genotoxic and Mutagenic Effects of Hypoxanthine and Alkylated Bases in DNA during Bacillus subtilis Sporulation

“…Our analysis using a B. subtilis strain carrying a transcriptional aag-lacZ fusion revealed that aag transcription is very low during exponential growth and early stages of sporulation but increases significantly during late stages of this developmental process. Of note, genes encoding a number of DNA repair proteins, including splB, ywjD, mfd, uvrA, and recA, exhibit similar expression patterns (45)(46)(47)(48). In addition, results from one transcriptomic study did report aag expression associated with sporulation stages T 7 and T 8 (49).…”

Role of Base Excision Repair (BER) in Transcription-associated Mutagenesis of Nutritionally Stressed Nongrowing Bacillus subtilis Cell Subpopulations

“…Suspensions of cells of interest, were processed for epifluorescence microscopy analysis as was previously described [17]. Alternatively , bacterial suspensions were analyzed in a Flow cytometer MoFlo XDP (Beckman Coulter, Brea, CA, USA), equipped with a 488 nm laser for excitation.…”

Roles of Bacillus subtilis RecA, Nucleotide Excision Repair, and Translesion Synthesis Polymerases in Counteracting Cr(VI)-Promoted DNA Damage

“…Activation of global stress responses following exposure to Cr(VI) has been documented in distinct bacteria (43)(44)(45). In B. subtilis, it has been shown that damaging factors that promote bulky DNA lesions activate the SOS response, resulting in derepression of genes encoding NER proteins, Y-DNA polymerases, and RecA, among others (33,34,36,38). Therefore, we first investigated whether Cr(VI) or reduced species derived from this metal were able to target DNA directly and to activate the SOS response.…”

“…DNA polymerases involved in TLS are distributed across all domains of life, including the human homologs REV3, REV1, and DNA polymerases , , and (37). Of note, when the NER and TCR pathways become insufficient for processing UV-promoted DNA lesions (pyrimidine dimers), these low-fidelity polymerases promote mutagenesis in B. subtilis sporangia (36,38,39).…”