Molecular characterization of Mre11-RAD50 proteins during Homologous Recombination Repair (HRR) in Toxoplasma gondii

DIEGO RUIZ; VALERIA TUROWSKI; WILLIAM SULLIVAN; SERGIO ANGEL

Mar del Plata

Congreso; XXXI Reunión anual de la Sociedad de Protozoología (SAP); 2019

Sociedades de Biociencia SAIC SAFE SAB SAP

The Homologous Recombination Repair (HRR) is critical to maintain the genome integrity during cell replication (late S / G2) but it has not been fullelucidated in T. gondii. HRR startswith recognition of damaged DNA follow by generation of resection ends forwhich Mre11-RAD50-Nbs1 (MRN) complex is required. In our research group it was observed that genome of T. gondii encodes 50% of HRR proteins described in yeast andmammals suggesting either divergence between these homologues as the presenceof parasite-specific components. In fact T.gondii harbours homologues of Mre11 and RAD50 proteins although no codingsequence relative to Nbs1 was found. In humans, MRN complex is composed by ahomodimer of Mre11 with endo / exonuclease activity tethered to RAD50 ATPase homodimerand Nbs1.TheMre11 gene of T. gondii (TgMre11) contains an open reading frame encoding a polypeptide with 38.41% of identityto its human homologue and 535 residues longer. Superimposition among 3D-modelof TgMre11 and HuMre11 crystal structure (RMS 0.84) showed three insertions of20 amino acids each on relevant regions for both dimerization and interactionwith other proteins or DNA. Thus, taking into account that Mre11 and RAD50 arepredicted to be essential genes in T.gondii, disclosing structural-functional differences between these proteinsand their human counterpart as well as characterize novel components of HRR in T. gondii might give insights aboutevolution of this pathway and help to identify novel drug targets.  Thiswork was supported by NIH 1 R01 AI129807-01 and PICT 2017-2485 grants.