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J. Biol. Chem., Vol. 283, Issue 4, 2265-2274, January 25, 2008
FAD24 Acts in Concert with Histone Acetyltransferase HBO1 to Promote Adipogenesis by Controlling DNA Replication*From the Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan Preadipocytes differentiate into adipocytes through approximately two rounds of mitosis, referred to as mitotic clonal expansion (MCE), but the events early in the differentiation process are not fully understood. Previously, we identified and characterized a novel gene, fad24 (factor for adipocyte differentiation 24), induced to express at the early stages of adipocyte differentiation. Although fad24 clearly has crucial roles in adipogenesis, its precise functions remain unknown. Here we show that the knockdown of fad24 by RNAi in 3T3-L1 preadipocytes repressed MCE. Moreover, FAD24 interacts with HBO1, a histone acetyltransferase and positive regulator of DNA replication initiation. The knockdown of hbo1 repressed MCE and adipogenesis, indicating that FAD24 acts in concert with HBO1 to promote adipogenesis by controlling DNA replication. Regarding the molecular mechanisms behind the regulation of DNA replication by fad24, we revealed that FAD24 co-localizes with HBO1 to chromatin during late mitosis, which is when the prereplication initiation complex is assembled. Furthermore, chromatin immunoprecipitation experiments indicated that FAD24 localizes to origins of DNA replication with HBO1. When fad24 expression was inhibited during adipocyte differentiation, the recruitment of HBO1 to origins of DNA replication was reduced. Thus, FAD24 controls DNA replication by recruiting HBO1 to origins of DNA replication and is required for MCE during adipocyte differentiation.
Received for publication, September 20, 2007 , and in revised form, November 12, 2007. * This work was supported in part by grants from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, and Japan Society for the Promotion of Science (JSPS). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 To whom correspondence should be addressed: Dept. of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan. Tel. and Fax: 81-52-836-3455; E-mail: imagawa{at}phar.nagoya-cu.ac.jp.
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