Abstract
EndoG, a member of the DNA/RNA non-specific ββα-metal family of nucleases, has been demonstrated to be present in many organisms, including Trypanosomatids. This nuclease participates in the apoptotic program in these parasites by migrating from the mitochondrion to the nucleus, where it takes part in the degradation of genomic DNA that characterizes this process. We now demonstrate that Leishmania infantum EndoG (LiEndoG) is an endo-exonuclease that has a preferential 5′ exonuclease activity on linear DNA. Regardless of its role during apoptotic cell death, this enzyme seems to be necessary during normal development of the parasites as indicated by the reduced growth rates observed in LiEndoG hemi-knockouts and their poor infectivity in differentiated THP-1 cells. The pro-life role of this protein is also corroborated by the higher survival rates of parasites that over-express this protein after treatment with the LiEndoG inhibitor Lei49. Taken together, our results demonstrate that this enzyme plays essential roles in both survival and death of Leishmania parasites.
Highlights
Members of the Endonuclease G (EndoG) family have been found in all organisms whose genomes have been fully sequenced
As described for other endonucleases [6], Leishmania infantum EndoG (LiEndoG) is able to produce nicks in double-stranded DNA (dsDNA), we proceeded to digest supercoiled plasmid DNA with increasing amounts of rLiEndoG expressed in E. coli
We show that LiEndoG is an endo-exonuclease that is able to generate single-strand breaks in circular supercoiled DNA whereas it has a preferential 59 exonuclease activity over linear DNA
Summary
Members of the Endonuclease G (EndoG) family have been found in all organisms whose genomes have been fully sequenced. One of the most important roles described for these enzymes is their participation in the apoptotic process whereby EndoGs translocate to the nucleus and contribute to the degradation of genomic DNA into oligonucleosomal fragments [1]. All of these proteins belong to the superfamily of non-specific bba-metallonucleases [2] and their nuclease activity depends on the presence of divalent cations such as Mg2+, Mn2+ or Co2+ whereas it is inhibited by moderate concentrations of monovalent cations such as K+ or Na+ [2,3,4]. This way, the full endo/ exonuclease activities found in mitochondria of lower eukaryotes were maintained [7]
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