Disease relevance of recA

• To determine whether the bipartite structure of inteins is mirrored by the functional independence of the protein-splicing domain, the entire endonuclease component was deleted from the Mycobacterium tuberculosis recA intein [1].
• The recA mutants will be a valuable tool for further development of BCG as an antigen delivery system to express foreign antigens and as a source of a genetically stable vaccine against tuberculosis [2].
• Transcriptional analysis of the recA gene in Streptomyces rimosus: identification of the new type of promoter [3].

High impact information on recA

• Guided by computer modeling studies, and taking advantage of genetic systems designed to monitor intein function, the 440-aa Mtu recA intein was reduced to a functional mini-intein of 137 aa [1].
• Mycobacterium tuberculosis recA harbors an intervening sequence in its open reading frame, presumed to encode an endonuclease (PI-MtuI) required for intein homing in inteinless recA allele [4].
• The RecA intein of Mycobacterium tuberculosis, a novel double-stranded DNA endonuclease, requires both Mn(2+) and ATP for efficient cleavage of the inteinless recA allele [5].
• Here we investigate the generality of each of these mechanisms by analysing the global response to DNA damage in both wild-type M. tuberculosis and a recA deletion strain of M. tuberculosis using microarrays [6].
• Of particular note most of the inducible genes with known or predicted functions in DNA repair did not depend on recA for induction [6].

Biological context of recA

• To investigate whether PI-MtuI possesses endonuclease activity, recA intervening sequence was cloned, overexpressed, and purified to homogeneity [4].
• We show here using transcriptional fusions to a reporter gene that the Mycobacterium tuberculosis recA gene is expressed from two promoters [7].
• Although a motif with only one mismatch to the Cheo box was found in the intergenic region between orf1 and orf2 these open reading frames were not DNA-damage inducible, nor was this motif required for regulation of recA expression [8].
• The recA locus of pathogenic mycobacteria differs from that of non-pathogenic species in that it contains large intervening sequences termed protein introns or inteins that are excised by an unusual protein-splicing reaction [9].
• The homology between the M. smegmatis sequence and that of Mycobacterium tuberculosis extended upstream of the recA coding region for 140 bp including a motif identical to the Cheo-box consensus sequence which has been shown to bind LexA [8].

Associations of recA with chemical compounds

• The recA mutants are sensitive to DNA-damaging agents and show increased susceptibility to metronidazole, the first lead compound active against the dormant M. tuberculosis complex [2].
• While both ATP and Mn(2+) were required for optimal cleavage of an inteinless recA allele (hereafter referred to as cognate DNA), Mg(2+) alone was sufficient for cleavage of ectopic DNA sites [10].

Other interactions of recA

• Reverse transcription/polymerase chain reaction analysis of M. smegmatis RNA demonstrated that recA and orf3 (recX) are within the same transcriptional unit [8].
• Upstream of the transcriptional start site for this promoter, sequence motifs resembling those observed previously at the RecA-independent, DNA damage-inducible recA promoter were identified, and the -10 motif was demonstrated by mutational analysis in transcriptional fusion constructs to be important for expression of Rv2719c [11].
• Examination of expression data for these genes following DNA damage identified 12 new genes which are most likely regulated by LexA as well as the known M. tuberculosis DNA damage-inducible genes recA, lexA, and ruvC [12].

Analytical, diagnostic and therapeutic context of recA

• Deletion of the recA gene from the chromosome was demonstrated by Southern hybridizations and by polymerase chain reaction (PCR) [13].

References