Non-canonical processing of DNA photodimers with Bacillus subtilis UV-endonuclease YwjD, 5'→3' exonuclease YpcP and low-fidelity DNA polymerases YqjH and YqjW.

It has been shown that mutation frequency decline (Mfd) and nucleotide excision repair (NER) deficiencies promote UV-induced mutagenesis in B. subtilis sporangia. As replication is halted in sporulating B. subtilis cells, in this report, we investigated if this response may result from an error-prone repair event involving the UV-endonuclease YwjD and low fidelity (LF) DNA synthesis. Accordingly, disruption of YwjD generated B. subtilis sporangia that were more susceptible to UV-C radiation than sporangia of the WT strain and such susceptibility increased even more after the single or simultaneous inactivation of the LF DNA polymerases YqjH and YqjW. To further explore this concept, functional His6-tagged YwjD and Y-DNA polymerases YqjH and YqjW were produced and purified to homogeneity. In vitro repair assays showed that YwjD hydrolyzed the phosphodiester bond immediately located 5´-end of a ds-DNA substrate bearing either, cyclobutane pyrimidine dimers (CPD), 6-4 photoproducts (6-4 PD) or Dewar isomers (DWI). Notably, the 6-4 PD and DWI but not the CPDs repair intermediaries of YwjD were efficiently processed by the LF polymerase YqjH suggesting that an additional 5'→3' exonuclease event was necessary to process PD. Accordingly, the LF polymerase YqjW efficiently processed the incision-excision repair products derived from YwjD and exonuclease YpcP attack over CPD-containing DNA. In summary, our results unveiled a novel non-canonical repair pathway that employs YwjD to incise PD-containing DNA and low fidelity synthesis contributing thus to mutagenesis, survival and spore morphogenesis in B. subtilis.

The RecA-Dependent SOS Response Is Active and Required for Processing of DNA Damage during Bacillus subtilis Sporulation.

The expression of and role played by RecA in protecting sporulating cells of Bacillus subtilis from DNA damage has been determined. Results showed that the DNA-alkylating agent Mitomycin-C (M-C) activated expression of a PrecA-gfpmut3a fusion in both sporulating cells' mother cell and forespore compartments. The expression levels of a recA-lacZ fusion were significantly lower in sporulating than in growing cells. However, M-C induced levels of ß-galactosidase from a recA-lacZ fusion ~6- and 3-fold in the mother cell and forespore compartments of B. subtilis sporangia, respectively. Disruption of recA slowed sporulation and sensitized sporulating cells to M-C and UV-C radiation, and the M-C and UV-C sensitivity of sporangia lacking the transcriptional repair-coupling factor Mfd was significantly increased by loss of RecA. We postulate that when DNA damage is encountered during sporulation, RecA activates the SOS response thus providing sporangia with the repair machinery to process DNA lesions that may compromise the spatio-temporal expression of genes that are essential for efficient spore formation.

Urinary excretion, osmolarity and electrolytes after bolus-injection of fenoterol in female rabbits.

The effects of bolus injections of 1.0-80.0 micrograms/kg body weight fenoterol on urinary excretion, osmolarity and electrolytes were studied in unanesthetized, water-loaded rabbits. In animals infused initially with isotonic solution over 2 h with 60 ml/h and thereafter over 10 h with 45 ml/h, urine excretion was 538 ml/12 h, sodium excretion was 65.4 mmol/12 h, and potassium excretion was 4.8 mmol/12 h. In animals injected with 5.0-80.0 micrograms/kg body weight fenoterol, a strong antidiuresis occurred, lasting for 2 (10.0 micrograms/kg) to 4 h (80.0 micrograms/kg). Due to the strong antidiuresis, urinary osmolarity was significantly elevated for 2 (10.0 micrograms/kg) to 3 h (80.0 micrograms/kg). The changes of sodium excretion after fenoterol injection were very similar to those of urine excretion. Maximum reduction of sodium excretion was found after injection of 10.0-80.0 micrograms/kg body weight fenoterol, the effect lasting for 1 h (10.0 micrograms/kg) to 4 h (80.0 micrograms/kg). Potassium excretion was significantly reduced after injection of 5.0-80.0 micrograms/kg body weight fenoterol. In contrast to all the other parameters measured, potassium excretion remained significantly reduced until the end of the infusion period in animals treated with 10.0-80.0 micrograms/kg body weight fenoterol and was not dose dependent. Our data presented in this work extend earlier findings in the rabbit in that bolus injection of fenoterol also results in a drastic decrease of urine and electrolyte excretion. The results are discussed with special reference for the management of acute fetal distress with betamimetics and to the development of pulmonary edema that has been shown to occur under therapy with betamimetics on both female rabbits and humans.