An Evolutionarily Conserved N-terminal Acetyltransferase Complex Associated with Neuronal Development

Abstract

We previously identified mNAT1 (murine N-terminal acetyltransferase 1) as an embryonic gene that is expressed in the developing brain and subsequently downregulated, in part, by the onset of N-methyl-D-aspartate (NMDA) receptor function. By searching the data base we discovered a second closely related gene, mNAT2. mNAT1 and mNAT2 are highly homologous to yeast NAT1, a gene known to regulate entry into the G 0 phase of the cell cycle. However, in the absence of further characterization, including evidence that mammalian homologues of NAT1 encode functional acetyltransferases, the significance of this relationship has been unclear. Here we focus on mNAT1. Biochemical analysis demonstrated that mNAT1 and its evolutionarily conserved co-subunit, mARD1, assemble to form a functional acetyltransferase. Transfection of mammalian cells with mNAT1 and mARD1 followed by immunofluorescent staining revealed that these proteins localize to the cytoplasm in both overlapping and separate compartments. In situ hybridization demonstrated that throughout brain development mNAT1 and mARD1 are highly expressed in areas of cell division and migration and are down-regulated as neurons differentiate. Finally, mNAT1 and mARD1 are expressed in proliferating mouse P19 embryonic carcinoma cells; treatment of these cells with retinoic acid initiates exit from the cell cycle, neuronal differentiation, and down-regulation of mNAT1 and mARD1 as the NMOA receptor 1 gene is induced. The results provide the first direct evidence that vertebrate homologues of NAT1 and ARD1 form an evolutionarily conserved N-terminal acetyltransferase and suggest that expression and down-regulation of this enzyme complex plays an important role in the generation and differentiation of neurons.

Expression of humanNAA11(ARD1B) gene is tissue-specific and is regulated by DNA methylation

“…25 Similar to the yeast Naa10p, mouse Naa10p alone does not display NAT activity. 12,26 However, hNaa10p alone was demonstrated to catalyze the acetylation of internal lysine residues in β-Catenin (CTNNB1), 15 Myosin Light Chain Kinase (MLCK), 22 and hNaa10p itself. 14 A shorter isoform of mNaa10p (mNaa10p_NP_001171436) was shown to stimulate the degradation of Hypoxia Inducible Factor 1a (Hif1α) by acetylating an internal lysine residue of the protein.…”

“…10 NatA was shown to regulate neuronal dendritic development in rodents 11 and it may also be involved in maintaining cellular proliferation. 12 Attenuation of NatA activity by silencing the expression of hNaa10p or hNaa15p with small interfering RNA results in a reduced viability and an increased level of apoptosis in HeLa cells. 13 Furthermore, hNaa10p was demonstrated to promote cancer cell proliferation.…”

NAA10 controls osteoblast differentiation and bone formation as a feedback regulator of Runx2

“…NAA10 is known to promote cell proliferation in human lung cancer by activating b-catenin 17 , to control cell migration in human fibrosarcoma by inactivating myosin light-chain kinase 18 , to control neuronal differentiation in mouse brain 25,26 and to promote prosate tumorigenesis by facilitating the androgen receptor signalling pathway 19 . However, NAA10 is generally believed (based on its ubiquitous expression) to have additional, as yet unknown, functions in mammalian cells.…”

The chaperones MPP11 and Hsp70L1 form the mammalian ribosome-associated complex

“…NMDA and ARD1 are homologs of yeast Nat1p and Ard1p, respectively. In yeast and mammals these two proteins are known components of the NatA complex (31,32). Using a crosslink approach we recently found that Nat1p is close to nascent polypeptides in yeast (4).…”