Laboratory of Interdisciplinary Biology (Molecular Genetics)


Associate Professor
mail takuro4 @

Interdisciplinary Biology


Graduate School of Science, Department of Biological Science



Research Theme

DNA replication is an essential reaction to maintain genetic information. For complete duplication of large and complex genome in eukaryotic cells, DNA replication initiates at large number of sites, called replication origins, on the chromosomes and the initiation process is tightly regulated by progression of cell cycle. We have been interested in how individual replication origin is activated and how origins are coordinated to ensure replication of all the genome in limited time period. We are also interested in the mechanisms to recover replication forks, which are stalled by shortage of deoxynucleotides or by DNA damage. Failure in the recovery results in cell death or genome instability that may cause a cancer in multicellular organisms. To understand these mechanisms at a molecular level, we use fission yeast, Schizosaccharomyces pombe, which has similarities with higher eukaryotes and thus is a suitable model organism to study the fundamental and general biological functions.

Genome-wide identification of replication origins

Chromosomes are confined into different chromatin structures relating with chromosome functions, such as centromere, mating type locus and telomeres. We are studying distribution of replication origins on fission yeast chromosomes by means of ChIP-chip analysis of replication factors and mapping of nascent DNA synthesized in early S phase. We identified 460 intergenic regions where Orc1 and Mcm6 are colocalized, as pre-replicative complex (pre-RC) sites, and 276 active origins that fire in early S phase in the presence of hydroxyurea.

Molecular mechanism of activation of replication origins

Replication origins are recognized by origin recognition complex (ORC) and minichromosome maintenance (MCM) complex is loaded depending on loading factors Cdc18/Cdc6 and Cdt1 in G1 phase. Assembly of several initiation factors is necessary for initiation of replication in S phase and this process is regulated by two conserved proteins kinases, cyclin-dependent kinase (CDK) and Dbf4-depedent kinase (DDK). By means of thermosensitive mutants of initiation factors, we identified the activation process is composed of three reactions, DDK-dependent Sld3-loading, DDK-CDK-dependent GINS-loading and Cdc45 loading.

Maintenance of Chromosome Integrity

Correct and precise duplication of genetic materials and faithful transmission of chromosomes to daughter cells are important for maintaining genome integrity. Defects in chromosome metabolisms can cause gross chromosomal rearrangements (GCRs) resulting in cell death as well as cancer and premature aging in multicellular organisms. To gain insights into the molecular mechanisms by which chromosome integrity is maintained, we have developed an assay system to detect GCRs using fission yeast and are searching for the genes essential for chromosome maintenance.

0Two-dimensional gel electrophoresis of replication intermediates at replication origin ars2004 on chromosome II in haploid fission yeast cells arrested in early S phase (A). DNA microarray results showing locations of newly synthesized DNA (green) and initiator protein Orc1 (brown) at the ars2004 locus (B).

1Assemby of replication initiation factors on fission yeast replication origins.

2Chromosome instability causes cell death and genetic diseases.


Su J, Xu R, Mongia P, Toyofuku N, Nakagawa T. Fission yeast Rad8/HLTF facilitates Rad52-dependent chromosomal rearrangements through PCNA lysine 107 ubiquitination. PLoS Genetics 17(7), e1009671 , (2021)

Onaka AT, Su J, Katahira, Y, Tang C, Zafar F, Aoki K, Kagawa W, Niki H, Iwasaki H, Nakagawa T. DNA replication machinery prevents Rad52-dependent single-strand annealing that leads to gross chromosomal rearrangements at centromeres. Commun Biol 3 , 202 - (2020)

Okita AK, Zafar F, Su J, Weerasekara D, Kajitani T, Takahashi TS, Kimura H, Murakami Y, Masukata H, Nakagawa T. Heterochromatin suppresses gross chromosomal rearrangements at centromeres by repressing Tfs1/TFIIS-dependent transcription. Commun Biol 2 , 17 - (2019)

Nakagawa T, Okita AK Transcriptional silencing of centromere repeats by heterochromatin safeguards chromosome integrity. Curr Genet 65(5) , 1089 - 1098 (2019)

Ogawa S, Kido S, Handa T, Ogawa H, Asakawa H, Takahashi TS, Nakagawa T, Hiraoka Y, Masukata H. Shelterin promotes tethering of late replication origins to telomeres for replication-timing control. EMBO J 37(15) , e98997 - (2018)

Terui F, Nagao K, Kawasoe Y, Taki K, Higashi TL, Tanaka S, Nakagawa T, Obuse C, Masukata H, Takahashi TS. Nucleosomes around a mismatched base pair are excluded via an Msh2-dependent reaction with the aid of SNF2 family ATPase Smarcad1. Genes Dev 32(11-12) , 806 - 821 (2018)

Zafar, F., Okita, AK., Onaka, AT., Su, J., Katahira, Y., Nakayama, J., Takahashi, TS., Masukata, H., Nakagawa, T. Regulation of mitotic recombination between DNA repeats in centromeres. Nucleic Acids Research 45 (19) , 11222 - 11235 (2017)

Onaka, AT., Toyofuku, N., Inoue, T., Okita, AK., Sagawa, M., Su, J., Shitanda, T., Matsuyama, R., Zafar, F., Takahashi, TS., Masukata, H., and Nakagawa, T. Rad51 and Rad54 promote noncrossover recombination between centromere repeats on the same chromatid to prevent isochromosome formation Nucleic Acids Research 44 (22) , 10744 - 10757 (2016)

Maki K, Inoue T, Onaka A, Hashizume H, Somete N, Kobayashi Y, Murakami S, Shigaki C, Takahashi TS, Masukata H, Nakagawa T. Abundance of prereplicative complexes (Pre-RCs) facilitates recombinational repair under replication stress in fission yeast. J Biol Chem, 286 , 41701 - 41710 (2011)


Department of Biological Sciences,
Graduate School of Science, Osaka University
1-1, Machikaneyama, Toyonaka, Osaka 560-0043
Phone: +81-6-6850-5432