Caracterizacion de la proteina codificada por el gen nat 5 humano estudio de su posible implicacion en el desarrollo de tumores

Abstract

Ami noterminal acetylation is a cotranslational modificatión occurring on most of the eucaryotic proteins. This modificatión has been widely studied in yeast, being catalyzed by the protein complexes NatA, NatB and Natc, and has been reported that the inhibition of each of these complexes resuíts in cell growth arrest, in mammals, 90 % of the soluble proteins are aminoterminally acetylated, but there are few examples demonstrating the biological significance of this type of acetylation. Nat5 is the human homologue of the catalytic subunit of the NatB complex in yeast and the aim of this work has been to characterize this protein. First at all we generated monoclonal and polyclonal antibodies that detect Nat5 protein only when it is overexpressed in mammalian cells. We also have tried to confirm in vitro the possible acetyltransferase activity of Nat5 but the absence of results suggest that this protein, as it happens in yeast, may need to interact with another subunit to exert its activity. we have seen that Nat5 is a cytoplasmàtic protein associated to ribosomes. The inhibition of Nat5 expression by different sírnas results in celi growth arrest, involving p53 dependent and independent mechanisms, and a greater susceptibility to an apoptotic cell death in HeLa, HepG2 and Hep3B cell lines. in accordance with these results, a gene expression analysis reveáis that Nat5 expression inhibition causes an overexpression of antiproliferative genes and downreguiation of genes involved in dna recombination and mitosis. we also have seen that Nat5 is overexpressed in mouse and human tumoral tissue confirming the relationship between Nat5 expression and cell proliferation, and suggesting a role for Nat5 in tumour development.