Streptococci have been considered to lack the classical SOS response, defined by increased mutation after UV exposure and regulation by LexA. Here we report the identification of a potential self-regulated SOS mutagenesis gene cassette in the Streptococcaceae family. Exposure to UV light was found to increase mutations to antibiotic resistance in @entity8211 cultures. The mutational spectra revealed mainly G: @entity11414 :T transitions, and Northern analyses demonstrated increased expression of a Y-family DNA polymerase resembling UmuC under DNA-damaging conditions. In the absence of the Y-family polymerase, @entity8211 cells were sensitive to UV light and to @entity1138 . Furthermore, the UV-induced mutagenesis was almost completely abolished in cells deficient in the Y-family polymerase. The gene encoding the Y-family polymerase was localized in a four-gene operon including two hypothetical genes and a gene encoding a HdiR homolog. Electrophoretic mobility shift assays demonstrated that @entity8211 HdiR binds specifically to an inverted repeat sequence in the promoter region of the four-gene operon. Database searches revealed conservation of the gene cassette in several @entity5858 species, including at least one genome each of @entity4195 , @entity5967 , @entity6419 , @entity5858 sanguinis, and @entity5858 strains. In addition, the umuC operon was localized in several mobile DNA elements of @entity5858 and Lactococcus species. We conclude that the hdiR-umuC-ORF3-ORF4 operon represents a novel gene cassette capable of mediating SOS mutagenesis among members of the Streptococcaceae.

Identification of a novel streptococcal gene cassette mediating SOS mutagenesis in XXXX .

@entity5967 :: ('1311', 'Species') :: ['Streptococcus agalactiae'] @entity1138 :: ('MESH:D016685', 'Chemical') :: ['mitomycin C'] @entity6419 :: ('28037', 'Species') :: ['Streptococcus mitis'] @entity4195 :: ('1314', 'Species') :: ['Streptococcus pyogenes'] @entity8211 :: ('1349', 'Species') :: ['S. uberis', 'Streptococcus uberis'] @entity5858 :: ('1308', 'Species') :: ['Streptococcus thermophilus', 'Streptococcus'] @entity11414 :: ('c|SUB|C||A', 'DNAMutation') :: ['C-->A']
@entity8211 :: (1349,Species) :: ['Streptococcus uberis']
