Autoacetylation regulates differentially the roles of ARD1 variants in tumorigenesis

ARD1 is an acetyltransferase with several variants derived from alternative splicing. Among ARD1 variants, mouse ARD1²³⁵ (mARD1²³⁵), mouse ARD1²³⁵ (mARD1²³⁵), and human ARD1²³⁵ (hARD1²³⁵) have been the most extensively characterized and are known to have different biological functions. In the present study, we demonstrated that mARD1²³⁵, mARD1²³⁵, and hARD1²³⁵ have conserved autoacetylation activities, and that they selectively regulate distinct roles of ARD1 variants in tumorigenesis. Using purified recombinants for ARD1 variants, we found that mARD1²³⁵, mARD1²³⁵, and hARD1²³⁵ undergo similar autoacetylation with the target site conserved at the Lys136 residue. Moreover, functional investigations revealed that the role of mARD1²³⁵ autoacetylation is completely distinguishable from that of mARD1²³⁵ and hARD1²³⁵. Under hypoxic conditions, mARD1²³⁵ autoacetylation inhibited tumor angiogenesis by decreasing the stability of hypoxia-inducible factor-1α (HIF-1α). Autoacetylation stimulated the catalytic activity of mARD1²³⁵ to acetylate Lys532 of the oxygen-dependent degradation (ODD) domain of HIF-1α, leading to the proteosomal degradation of HIF-1α. In contrast, autoacetylation of mARD1²³⁵ and hARD1²³⁵ contributed to cellular growth under normoxic conditions by increasing the expression of cyclin D1. Taken together, these data suggest that autoacetylation of ARD1 variants differentially regulates angiogenesis and cell proliferation in an isoform-specific manner.