Journal Article

ARA54 is involved in transcriptional regulation of the <i>cyclin D1</i> gene in human cancer cells

Hirotoshi Kikuchi, Chiharu Uchida, Takayuki Hattori, Tomoyasu Isobe, Yoshihiro Hiramatsu, Kyoko Kitagawa, Toshiaki Oda, Hiroyuki Konno and Masatoshi Kitagawa

in Carcinogenesis

Volume 28, issue 8, pages 1752-1758
Published in print August 2007 | ISSN: 0143-3334
Published online May 2007 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgm120
ARA54 is involved in transcriptional regulation of the cyclin D1 gene in human cancer cells

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Cyclin D1 is one of the major enhancers of cell cycle progression and its expression is regulated in several growth stimulatory signaling pathways. ARA54 is an androgen receptor (AR) co-activator that enhances AR-dependent transcriptional activation. Although expression of ARA54 mRNA is observed in a variety of human tissues at low levels, the AR- or androgen-independent function of ARA54 in those tissues remains unclear. In this study, we identified a novel role for ARA54 in the regulation of cyclin D1 expression in the absence of AR stimulation in human cancer cells. Depletion of endogenous ARA54 by small interfering RNA decreased both the protein and mRNA levels of cyclin D1. These changes did not result from a reduction in the half-life of either the protein or the mRNA, but from suppression of cyclin D1 gene transcription. In T98G cells, depletion of ARA54 increased the population of cells in G1 phase, but reduced the population of cells in S phase, leading to a significant increase in the G1/S ratio and impaired cell growth. Furthermore, the amount of ARA54 mRNA appeared to positively correlate with cyclin D1 mRNA levels in specimens of clinical colon carcinomas, indicating that ARA54 is not only involved in the regulation of cyclin D1 expression in cultured cell lines but also in clinical cancer specimens. These results suggest that ARA54 might participate in enhancing cell cycle progression and cell proliferation via induction of cyclin D1.

Journal Article.  4453 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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