Maki Asano

Focus

DNA replication initiation, ORC1, Cdc6, E2F, Drosophila, endoreplication, proliferation, developmental regulation

Research interests

Our laborataory studies DNA replication initiation factors and the roles they play to regulate different modes of DNA replication during organism develompent.

We employ molecular, biochemical, and genetic approaches in our reserach.  We use Drosophila as a model system for the folllowing reasons:

1)  Most of the components involved in DNA replication regulation are remarkably conserved in flies and mammals and therefore our findings will be directly applicable to mammals.

2) During Drosophila development, a number of tissues and cell types offer excellent opoprtunities to study cell cycle progression in unperturbed cells of the intact animal.

3) An unparalleled combination of genetic and molecular tools is available for use in Drosophila.  Prominent among these are the ability to easily prepare transgenic animals or mutants by gene-targeting, highly developed technology for tissue- and cell type-specific mis-expression in vivo, and a complete and well annotated genomic sequence.

Our current research projects are:

1) Molecular mechanisms of endoreplication initiation: we have discovered that motitic DNA replication and endoreplication use different pre-Replication Complex (pre-RC) components (Park & Asano, 2008). We will identify pre-RC components specific to endoreplication using genetic (ex. Production of cdc6 mutants) and biochemical (ex. Purification of Cdc6 and Cdt1/Dup interacting proteins) approaches.


2) Molecular mechanisms of ORC1 function outside of DNA replication: Although the ORC has a primary role in directing the initiation of DNA replication, we and others have suggested that it plays an important role in other aspects of the cell cycle such as chromosome condensation, chromosome segregation, and cytokinesis as well as non-cell cycle events such as heterochromatin-associated transcriptional silencing and control of synaptic plasticity. We will identify and characterize new ORC1-interacting factors, i.e. its functional partner in each function.


3) Identification of new targets of Anaphase Promoting Complex (APC): We have identified a novel APC motif, the “ORC1-destruction box” (O-box), which mediates ORC1 degradation by APC (Araki et al., 2005). Using combination of purified ubiquitination assays in vitro and protein degradation assay in vivo in cell culture and transgenic flies we will identify new O-box proteins and their involvement in cell cycle control.

 

Publications

• Park SY, Asano M. The origin recognition complex is dispensable for endoreplication in Drosophila. Proc Natl Acad Sci U S A. 2008 Aug 26;105(34):12343-8.
• Narbonne-Reveau K, Senger S, Pal M, Herr A, Richardson HE, Asano M, Deak P, Lilly MA. APC/CFzr/Cdh1 promotes cell cycle progression during the Drosophila endocycle. Development. 2008 Apr;135(8):1451-61
• Wu Q, Guo Y, Yamada A, Perry JA, Wang MZ, Araki M, Freel CD, Tung JJ, Tang W, Margolis SS, Jackson PK, Yamano H, Asano M, Kornbluth S. A role for Cdc2- and PP2A-mediated regulation of Emi2 in the maintenance of CSF arrest. Curr Biol. 2007 Feb 6;17(3):213-24.
• Araki M, Yu H, Asano M. A novel motif governs APC-dependent degradation of Drosophila ORC1 in vivo. Genes Dev. 2005 Oct 15;19(20):2458-65
• Okudaira K, Ohno K, Yoshida H, Asano M, Hirose F, Yamaguchi M. Transcriptional regulation of the Drosophila orc2 gene by the DREF pathway. Biochim Biophys Acta. 2005 Dec 30;1732(1-3):23-30.
• Araki M, Wharton RP, Tang Z, Yu H, Asano M. Degradation of origin recognition complex large subunit by the anaphase-promoting complex in Drosophila. EMBO J. 2003 Nov 17;22(22):6115-26.
• Asano M, Wharton RP. E2F mediates developmental and cell cycle regulation of ORC1 in Drosophila. EMBO J. 1999 May 4;18(9):2435-48.
• Asano M, Nevins JR, Wharton RP. Ectopic E2F expression induces S phase and apoptosis in Drosophila imaginal discs. Genes Dev. 1996 Jun 1;10(11):1422-32.
• Ito K, Asano M, Hughes P, Kohzaki H, Masutani C, Hanaoka F, Kerppola T, Curran T, Murakami Y, Ito Y. c-Jun stimulates origin-dependent DNA unwinding by polyomavirus large Tantigen. EMBO J. 1996 Oct 15;15(20):5636-46.