Arrest Defective 1 Autoacetylation Is a Critical Step in Its Ability to Stimulate Cancer Cell Proliferation
ABSTRACT The N-acetyltransferase arrest defective 1 (ARD1) is an important regulator of cell growth and differentiation that has emerged recently as a critical molecule in cancer progression. However, the regulation of the enzymatic and biological activities of human ARD1 (hARD1) in cancer is presently poorly understood. Here, we report that hARD1 undergoes autoacetylation and that this modification is essential for its functional activation. Using liquid chromatography-tandem mass spectrometry and site-directed mutational analyses, we identified K136 residue as an autoacetylation target site. K136R mutation abolished the ability of hARD1 to promote cancer cell growth in vitro and tumor xenograft growth in vivo. Mechanistic investigations revealed that hARD1 autoacetylation stimulated cyclin D1 expression through activation of the transcription factors beta-catenin and activator protein-1. Our results show that hARD1 autoacetylation is critical for its activation and its ability to stimulate cancer cell proliferation and tumorigenesis.
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ABSTRACT: Arrest defective 1 (ARD1) is an acetyltransferase that is highly conserved across organisms, from yeasts to humans. The high homology and widespread expression of ARD1 across multiple species and tissues signify that it serves a fundamental role in cells. Human ARD1 (hARD1) has been suggested to be involved in diverse biological processes, and its role in cell proliferation and cancer development has been recently drawing attention. However, the subcellular localization of ARD1 and its relevance to cellular function remain largely unknown. Here, we have demonstrated that hARD1 is imported to the nuclei of proliferating cells, especially during S phase. Nuclear localization signal (NLS)-deleted hARD1 (hARD1ΔN), which can no longer access the nucleus, resulted in cell morphology changes and cellular growth impairment. Notably, hARD1ΔN-expressing cells showed alterations in the cell cycle and the expression levels of cell cycle regulators compared to hARD1 wild-type cells. Furthermore, these effects were rescued when the nuclear import of hARD1 was restored by exogenous NLS. Our results show that hARD1 nuclear translocation mediated by NLS is required for cell cycle progression, thereby contributing to proper cell proliferation.PLoS ONE 08/2014; 9(8):e105185. DOI:10.1371/journal.pone.0105185 · 3.53 Impact Factor
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ABSTRACT: ARD1 is present in various species and has several variants derived from alternative splicing of mRNA. Previously, we reported differential biological functions and cellular distributions of mouse ARD1 (mARD1) variants. However, in comparison to mARD1 variants, human ARD1 (hARD1) variants have been rarely studied. In this study, we characterized a hARD1 variant, hARD1131 and investigated its cellular activities. hARD1131 mRNA was isolated from HeLa cells and sequenced. Sequence alignment revealed that, compared to hARD1235, the most common form of hARD1, the mRNA sequence encoding hARD1131 possesses an altered reading frame due to a 46-bp deletion. Thus, hARD1131 and hARD1235 differ in their C-terminal regions with a partially deleted acetyltransferase domain at the C-terminus of hARD1131. Moreover, hARD1131 and hARD1235 showed different subcellular localizations and biological functions. hARD1131 was mostly localized in the cell nucleus, whereas hARD1235 was primarily localized in the cytoplasm. In addition, hARD1235 stimulated cell prolifer-ation by upregulation of cyclin D1, however hARD1131 had no influence on cyclin D1 expression and cell growth. Because hARD1235 enhances cell proliferation by its autoacetylation activity, we examined the autoacetylation activity of hARD1131 and observed that this function was absent in hARD1131. These results suggest that human ARD1 variants have different effects on cell prolifer-ation, which may result from distinct subcellular localizations and autoacetylation activities.International Journal of Oncology 11/2014; 46(2). DOI:10.3892/ijo.2014.2770 · 2.77 Impact Factor
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ABSTRACT: Spermatogenesis refers to the developmental process of male germ cell formation from the spermatogonial stem cell to mature spermatozoa. The progression of male germ cells through the different phases of development, along with changes in cellular size and morphology, involves a coordinated change in their gene expression program at both the transcript and protein levels. It is well known that the stability, biological activity and cellular localization of proteins are regulated by post-translational modifications. In this review, we provide a brief update of current knowledge about the role of protein acetylation in mammalian spermatogenesis. Based on recent findings specific examples were cited to illustrate how these modifications are involved in controlling the different events that are important to the proper development of male germ cells.