ARD1-mediated acetylation of protein arginine methyltransferase 5 (PRMT5) regulates its methyltransferase activity and cancer cell proliferation

Abstract

Arrest defective 1 (ARD1) was first identified in Saccharomyces cerevisiae and it has N-terminal acetyltransferase activity. Mammalian homologues of ARD1 acetylate the N-terminal α-amino group of some proteins associated with N-acetyltransferase. In addition, mammalian ARD1 can also acetylate the ε-amino group of lysine such as HIF-1α, β-catenin and myosin light chain. It was also reported that ARD1 has an important role in regulation of cell growth and differentiation through acetylation that has been known as a critical molecule in cancer progression. It was required to find more substrates of ARD1, binding partners of ARD1 were investigated and our group found some binding partners of ARD1. In this study, it was found that one of binding partners of ARD1 is protein arginine methyltransferase 5 (PRMT5) and ARD1 regulates its major function. PRMT5 is one of the protein arginine methyltransferases (PRMTs), which can catalyze the transfer of one or two methyl groups to the guanidine nitrogen atoms of arginine. PRMTs are mainly classified as type Ⅰ and type Ⅱ enzymes. These two types of enzymes catalyze the formation of a mono methylated intermediate and type Ⅰ PRMTs (PRMT1, 3, 4, 6, and 8) further catalyze the formation of asymmetric dimethylation of arginine residues, and type Ⅱ PRMTs (PRMT5, 7, and 9) catalyze the formation of symmetric dimethylation of arginine residues. Protein Arginine Methyltransferase 5 (PRMT5) is type Ⅱ PRMT and the essential enzyme involved in a variety of biological processes such as tumorigenesis, transcription, differentiation and spliceosome assembly via histone and other proteins methylation. However, little is known about the upstream signal of PRMT5 function. Here, we suggest that ARD1 acetylates protein arginine methyltransferase 5 (PRMT5) and this modification is essential for functional activation of PRMT5. Using liquid chromatography-tandem mass spectrometry and site-directed mutational analyses, we identified K490 residue as an acetylation target site. K490R mutation abolished the ability of PRMT5 to methylate histone H4 and to promote cancer cell growth. Our results show that ARD1-mediated acetylation of PRMT5 is critical for PRMT5 methyltransferase activity and its ability to stimulate cancer cell growth and proliferation.