Comparison of the Properties of PARP1 and HPF1 in Naked Mole-Rat and Human.

DNA repair is the main mechanism for maintaining genome stability in living organisms and is considered one of the key factors influencing the maximum lifespan of mammals. Two proteins are of particular interest in the context of studying molecular basis of longevity: the key DNA repair regulator poly(ADP-ribose) polymerase 1 (PARP1) and the recently discovered modulator of its activity, histone poly(ADP-ribosyl)ation factor 1 (HPF1). This work analyzes the results of comparative analysis of the primary structures of PARP1 and HPF1, as well as examples of computer modeling of the orthologous proteins PARP1 and HPF1 and their complexes. As part of comparative assessment of the properties of recombinant PARP1 and HPF1 from two long-lived mammals, the naked mole-rat and human, we compared their amino acid sequences, stability of these protein structures under the action of denaturing agents, strength of the PARP1 ortholog complexes with DNA, effect of the recombinant HPF1 proteins on PARP1 automodification, and the results of 3D modeling of the PARP1-HPF1 complexes. Despite the differences in primary structures, the naked mole-rat and human PARP1 exhibited similar kinetic parameters in the poly(ADP-ribosyl)ation reaction catalyzed by these enzymes, as well as similar levels of stability of the complexes formed by the PARP1 orthologs with a DNA duplex. Due to predominantly hydrophobic nature of amino acid substitutions in the PARP1 sequence, the naked mole-rat PARP1 proved to be more thermostable and resistant to the denaturing effect of urea, whereas differences in the primary structures of the HPF1 orthologs did not result in any difference in their stability. At the same time, both HPF1 proteins (homologous and heterologous) stimulated human PARP1 in the auto-poly(ADP-ribosyl)ation reaction with comparable efficiency. We suggest that the observed effects are associated with the differences in the primary structures of PARP1 proteins. The obtained results may serve as a foundation for further comparative studies of the properties of PARP family proteins in both naked mole-rats and humans, as well as in other mammals.