Regulation and Destabilization of HIF-1α by ARD1-Mediated Acetylation

posttranslational phosphorylation of HIF-1␣ and promotes the transcriptional activity of HIF-1 (Richard et Hypoxia-inducible factor 1 (HIF-1) plays a central role al., 1999). According to a recent report, the hydroxylation in cellular adaptation to changes in oxygen availability. of asparagine (Asn803), located in the C-terminal trans-Recently, prolyl hydroxylation was identified as a key activation domain (C-TAD) of HIF-1␣, inhibits interaction regulatory event that targets the HIF-1␣ subunit for with the p300/CBP coactivator and reduces the tran-proteasomal degradation via the pVHL ubiquitination scriptional activity of HIF-1 during normoxic conditions complex. In this report, we reveal an important func-(Hewitson et al., 2002; Lando et al., 2002a, 2002b). tion for ARD1 in mammalian cells as a protein acetyl-Thus, the modulation of HIF-1␣ stability and its activa-transferase by direct binding to HIF-1␣ to regulate its tion involve multiple proteins and several posttransla-stability. We present further evidence showing that tional modifications. Until recently, studies of posttrans-ARD1-mediated acetylation enhances interaction of lational modifications of HIF-1␣ were restricted to HIF-1␣ with pVHL and HIF-1␣ ubiquitination, sug-hydroxylation, ubiquitination, and phosphorylation. gesting that the acetylation of HIF-1␣ by ARD1 is criti-Other posttranslational modifications of HIF-1␣ have not cal to proteasomal degradation. Therefore, we have been defined. concluded that the role of ARD1 in the acetylation of In the present study, we used the yeast two-hybrid HIF-1␣ provides a key regulatory mechanism underly-system to identify proteins that interact with the ODD ing HIF-1␣ stability. domain of HIF-1. One of the HIF-1␣-interacting clones, mouse ARD1, shares 57% identity with the ARD1 acetyl-Introduction transferase sequence of Saccharomyces cerevisiae (Tribioli et al., 1994). ARD1 is required for the expression Eukaryotic cells sense oxygen and adapt to hypoxia by of protein N-acetyltransferase (NAT) activity in lower regulating a number of genes. In mammalian cells, the eukaryotes and bacteria (Tribioli et al., 1994; Park and transcriptional complex HIF-1 plays an essential role in Szostal, 1992; Ingram et al., 2000). However, its function cellular and systemic oxygen homeostasis (Iyer et al., in mammalian cells has not been defined. 1998; Semenza, 2000). HIF-1 stimulates the transcription Acetylation is a posttranslational modification of proof genes, such as erythropoietin and VEGF, whose proteins , with histones the best-known example (Kou-tein products function to either increase oxygen avail-zarides, 2000). Several enzymes are reported as histone ability by promoting erythropoiesis and angiogenesis, acetyltransferases; these include PCAF, p300/CBP, or activates genes involved in glucose transport and SRC1, and MOZ (Kouzarides, 1999). Recently, …