[Cloning of a new murine gene coding for a protein immunologically related to RecA protein from Escherichia coli]

Using the testis-specific murine cDNA library immunoscreening with the affine-purified polyclonal antibodies to the E. coli RecA protein, the 1730-bp fragment of the novel mouse gene was cloned. Northern hybridization of total RNA samples from mouse somatic and meiotic tissues showed that this gene was specifically expressed in mouse testis, producing a transcript of about 10 kb in size. Analysis of the cloned cDNA sequence revealed the presence of the-AATAAA-polyadenylation site at its end, indicating that the cloned fragment represented the end part of the corresponding gene. Comparative sequence analysis revealed that the plus-chain of the cloned fragment contained motifs of the mouse RAD50 gene; the 378-bp fragment of the minus-chain showed 96% homology with the Homo sapiens Hd741-f cDNA fragment; and the whole minus-chain was by 50% homologous to the prokaryotic FTSZ/A genes. The cloned fragment contained two reading frames located in the plus- and minus-chains, respectively. The presumptive 44-kDa protein encoded by the plus-chain (sense) open reading frame contained serine-, proline-, and threonine-rich regions and was 25 to 30% homologous to a number of nuclear DNA-binding proteins of eukaryotes. Although analysis of the similarity between the 44-kDa protein and the E. coli RecA protein did not show any significant homology between them, it revealed their identity by five amino-acid residues involved in the formation of the epitope that recognized the paratope of the RecA protein antibody for subsequent epitope-paratope binding of these proteins.