Abstract
BackgroundHuman Nα-acetyltransferase complex B (hNatB) is integrated by hNaa20p (hNAT5/hNAT3) and hNaa25p (hMDM20) proteins. Previous data have shown that this enzymatic complex is implicated in cell cycle progression and carcinogenesis. In yeast this enzyme acetylates peptides composed by methionine and aspartic acid or glutamic acid in their first two positions respectively and it has been shown the same specificity in human cells.MethodsWe have silenced hNAA20 expression in hepatic cell lines using recombinant adenoviruses that express specific siRNAs against this gene and analyzed cell cycle progression and apoptosis induction after this treatment. Immunopurified hNatB enzymatic complexes from human cell lines were used for analyzing hNatB in vitro enzymatic activity using as substrate peptides predicted to be acetylated by NatB.ResultshNAA20 silencing in hepatic cell lines reduces cell proliferation in a p53 dependent and independent manner. At the same time this treatment sensitizes the cells to a proapototic stimulus. We have observed that the hNatB complex isolated from human cell lines can acetylate in vitro peptides that present an aspartic or glutamic acid in their second position as has been described in yeast.ConclusionhNatB enzymatic complex is implicated in cell cycle progression but it exerts its effects through different mechanisms depending on the cellular characteristics. This is achievable because it can acetylate a great number of peptides composed by an aspartic or glutamic acid at their second residue and therefore it can regulate the activity of a great number of proteins.
Highlights
Human N -acetyltransferase complex B is integrated by hNaa20p and hNaa25p proteins
NatB enzymatic complex is integrated by the catalytic subunit Naa20p and the auxiliary subunit Naa25p, as has been observed in yeast and human cells [3,4,5]
Results and discussion hNaa20p implication in cellular proliferation It has been previously reported that Human N -acetyltransferase complex B (hNatB) inhibition generates a reduction of cellular proliferation [5,12]
Summary
Human N -acetyltransferase complex B (hNatB) is integrated by hNaa20p (hNAT5/ hNAT3) and hNaa25p (hMDM20) proteins. Previous data have shown that this enzymatic complex is implicated in cell cycle progression and carcinogenesis. In yeast this enzyme acetylates peptides composed by methionine and aspartic acid or glutamic acid in their first two positions respectively and it has been shown the same specificity in human cells. NatB enzymatic complex is integrated by the catalytic subunit Naa20p and the auxiliary subunit Naa25p, as has been observed in yeast and human cells [3,4,5]. Proteins with Met-Asp-, Met-Glu-, Met-Asn- and Met-Met- amino termini constitute potential NatB substrates. Whereas Met-Asp- and Met-Glu- termini appear to be acetylated in 100% of the cases, only some of the experimentally investigated Met-Asn- and Met-Mettermini have been found to constitute true NatB targets [6]. In the meantime all mammals proteins with Met-Asnand Met-Met- termini analyzed present the methionine acetylated and they are considered as NatB substrates [2]
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