Unveiling the structural and functional role of insertions in Mre11 nuclease from Toxoplasma gondii

DIEGO M. RUIZ; VALERIA R. TUROWSKI

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Biofísica; 2022

Sociedad Argentina de Biofísica

The Mre11 protein is critical to several physiological processes such as DNA repair andmeiosis being its endo- and exo-nuclease activities required to maintain genomic stability. Indeed, hypomorphic mutations in the Mre11 gene causes ionizing radiation sensitivity, ataxia-telangiectasia-like disorder (ATLD) and cancer-predisposition. Nuclease activities are provided by an N-terminal domain (core) which is relatively similar in Mre11 from all species. In eukaryotes, there are several hundred additional C-terminal amino acids that are poorly conserved and without known catalytic activity. Recently, a genome-wide CRISPR-Cas9 knockout screening from Toxoplasma gondii predicted that gene encoding Mre11 (TgMre11) might be essential for parasite viability, becoming this enzyme in a promising target to improve anti-toxoplasmic treatments. Thus, our main objective is to elucidate the biochemical and biophysical features of TgMre11 to find molecular determinants for future drug discovery. Results from superimposition among 3D-model to TgMre11 and crystal structure of human enzyme (HsMre11) showed three insertions of 20 amino acids each located at relevant regions for both dimerization as interaction with other proteins and DNA. The time courses to endonuclease activity showed that TgMre11 is more active than HsMre11, however when differential region in α2β3 loop of TgMre11 was removed enzyme activity decreased. In addition, this deletion did not affect the apparent oligomeric state of TgMre11. This finding shed light on the functional relevance of extra residues in TgMre11 α2β3 loop highlighting its potential as target to design of specific inhibitors.