IDENTIFICATION OF HOMOLOGOUS RECOMBINATION MACHINERY IN Toxoplasma gondii

IGNACIO M FENOY; SILVINA S. BOGADO; SUSANA M. CONTRERAS; SERGIO O. ANGEL

Congreso; XXVII Reunión Anual Sociedad Argentina de Protozoología; 2015

Toxoplasma gondii is a medical and veterinary relevant pathogen of phylum Apicomplexa. In humans, asexual replication is characterized by two forms: the rapidly growing ?tachyzoites?, sensitive to host immune system and several drugs, and the slowly dividing encysted ?bradyzoites? that evade both the host immune response and anti-toxoplasma drugs. Notably, tachyzoites replicate with a doubling time of 5 -9 hours. Such quick and uninterrupted rounds of DNA replication might trigger replication stress as suggested by the observation of increased basal levels of the replication-stress marker H2A.X in T. gondii tachzyoite. DNA replication and damage repair machinery is poorly characterized in T. gondii. In the present work we aim to identify the homologous recombination (HR) machinery in T. gondii. For this, we performed an in silico study for proteins involved in HR in www.toxodb.org database. For the search we used the well characterized proteins of Saccharomyces cerevisiae and Human. We look for sequence homology by BLAST analysis and the presence of correct protein domains. We found 50 proteins conserved of a pool of 90 well-known proteins. These proteins include the core machinery implicated in HR Mre11, Rad50, Exo1 exonuclease, Rad51, Mre11, EXO, BLM and RecQ helicases. Proteins containing a BRCA1 C terminus (BRCT) domain such as BRCA1, 53BP1 or Rad9/Crb2 were not identified. However, by using a different approach by means of the BRCT domain amino acid sequence of human BRCA1, we identified an hypothetical protein that could represent a putative BRCT domain (near 53 residues) containing protein. In conclusion, we found that basic machinery is conserved in T. gondii, but many proteins involved in double strand break recognition and HR repair are poorly conserved and represent an interesting field for futures studies in T. gondii biology.