Characterization of the proteins LmRad9 and LmRad1 in the DNA damage response of Leishmania major

Abstract

Our laboratory investigates the expression and function of the protein complex 9-1-1 (Rad9-Rad1-Hus1) in the DNA Damage Response (DDR) of the protozoan parasite Leishmania. In other eukaryotes this complex acts in the sensing of DNA Damage and in the signaling required for cell cycle arrest and proper DNA repair. We have shown that the Hus1 homologue in the parasite participates in the DDR and also interacts with a Rad9 homologue in vivo. Both, LmHus1 and LmRad9 also participate in telomere maintenance. We showed that LmHus1 deficiency interfered with a proper replicative stress checkpoint. We also demonstrated that LmHus1 is well conserved in the eukaryote lineage, while LmRad9 presents a much lower conservation. Moreover, the parasite genome does not seem to encode a Rad1 homologue. These data suggest a peculiar mechanism for the detection and signaling of DNA Damage. The study of this complex in Leishmania will contribute to the understanding not only of the parasite genome homeostasis, but also, of the evolution of the DDR in eukaryotes. Therefore, the aim of this proposal is (i) to identify the possible homologue of Rad1 in L. major; (ii) study the expression and function if its product; (iii) investigate the architecture of the 9-1-1 complex in the parasite; and (iv) expand the functional characterization of the proteins LmHus1 and LmRad9. (AU)