UV-induced increase in RNA polymerase activity in Xanthomonas oryzae pathovar oryzae

UV radiation is thought to inhibit transcriptional elongation, as a result of the formation of pyrimidine dimers in the DNA template, as well as to ac tivate specific transcription factors. However, the effect of W radiation o n the enzymatic activity of RNA polymerase has remained unknown. With the u se of an in vitro assay, UV irradiation of Xanthomonas oryzae pathovar oryz ae has now been shown to increase RNA polymerase activity. This effect was maximal at a UV dose of similar to 12J m(-2) and at similar to 60 min after irradiation. It was also not inhibited by pretreatment of cells with chlor amphenicol, an inhibitor of protein synthesis. Immunoprecipitation with ant ibodies to the RNA polymerase core enzyme revealed that exposure of the bac terial cells to W radiation induced the association of the core enzyme with a protein of similar to 29 kDa, These results demonstrate that W radiation increases the activity of RNA polymerase, and they suggest that this effec t may be related to the repair of DNA damage.