DNA polymerase lambda (Pol lambda), a novel eukaryotic DNA polymerase witha potential role in meiosis

A new gene (POLL) encoding a novel DNA polymerase (Pol lambda) has been ide ntified at mouse chromosome 19. Murine Pol lambda, consisting of 573 amino acid residues, has a 32% identity to Poi beta, involved in nuclear DNA repa ir in eukaryotic cells. It is interesting that Pol lambda contains all the critical residues involved in DNA binding, nucleotide binding and selection , and catalysis of DNA polymerization, that are conserved in Poi beta and o ther DNA polymerases belonging to family X. Murine Poi lambda, overproduced in Escherichia coli, displayed intrinsic DNA polymerase activity when asse ssed by in situ gel analysis. Poi lambda also conserves the critical residu es of Poi beta required for its intrinsic deoxyribose phosphate lyase (dRPa se) activity. The first 230 amino acid residues of Poi lambda, that have no counterpart in Pol beta, contain a BRCT domain, present in a variety of ce ll-cycle check-point control proteins responsive to DNA damage and proteins involved in DNA repair. Northern blotting, in situ hybridization analysis and immunostaining showed high levels of Poi lambda specifically expressed in testis, being developmentally regulated and mainly associated to pachyte ne spermatocytes. These first evidences, although indirect, suggest a poten tial role of Pol lambda in DNA repair synthesis associated with meiosis. (C ) 2000 Academic Press.