Enhanced expression of recX in Mycobacterium tuberculosis owing to a promoter internal to recA.
RecX is a small protein that interacts with, and modulates the activity of, RecA protein. In mycobacteria the recX gene is located immediately downstream of the recA gene, and the coding regions overlap. It has previously been shown that these two genes are co-transcribed in Mycobacterium smegmatis. In this study we examine the expression of recX in Mycobacterium tuberculosis. In addition to being co-transcribed with recA from the DNA-damage inducible recA promoters, we identify a constitutive recX promoter located within the recA coding sequence that is strong enough to make a significant contribution to the expression level of recX in the absence of DNA damage. Intriguingly, this promoter is inactivated in M. smegmatis by a critical base change in the -10 promoter motif, which probably accounts for the lower level of expression of recX relative to recA that we observed in that species. It is possible that this difference in relative expression influences RecA functions including the response to DNA damage of LexA-regulated genes.
Division of Mycobacterial Research, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
Lorna N
LN
Forse
Joanna
J
Houghton
Elaine O
EO
Davis
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017124:Conserved Sequence / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D016366:Open Reading Frames / Q000235:genetics; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D012329:RNA, Bacterial / Q000235:genetics; D011938:Rec A Recombinases / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D016415:Sequence Alignment; D013045:Species Specificity; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D012329:RNA, Bacterial; C430523:RecX protein, Xanthomonas campestris; D011938:Rec A Recombinases
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