Nuclear DNA polymerase beta from Leishmania infantum. Cloning, molecular analysis and developmental regulation

We have identified a novel polymerase beta (Pol beta)-like enzyme from Leis hmania infantum, a parasite protozoon causing disease in humans. This prote in, named Li Poll P, shows a nuclear localization that contrasts with the m itochondrial localization of Pol P from Crithidia fasciculata, a closely re lated parasite, the only polymerase beta described so far in Trypanosomatid ae. Li Pol P, that belongs to the DNA polymerase X family, displays an evol utionarily conserved Pol beta -type DNA polymerase core, in which most of t he key residues involved in DNA binding, nucleotide binding, dRPase and pol ymerization catalysis are conserved. In agreement with this, Li Pol P, over produced in Escherichia coli, displayed intrinsic DNA polymerase activity. Cell synchronization experiments showed a correlation between both Li Pol b eta mRNA and protein levels along the parasite cell cycle. Analysis of thes e parameters at the different growth phases of the parasite, from the proli ferative (non-infective) logarithmic phase to the non-dividing (highly infe ctious) stationary phase, showed high levels of Li Pol P at the infective p hase of the parasite. The data suggest a role of Li Poll P in base excision repair in L.infantum, a parasite usually affected by oxygen stress environ ments into the macrophage host cells.