Báo cáo khoa học: Dynamics in the transmission of genetic information: from meiosis to postmeiotic events doc

MINIREVIEW SERIES Dynamics in the transmission of genetic information: from meiosis to postmeiotic events Wataru Kagawa and Hitoshi Kurumizaka Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan Meiosis is a special type of cell division that generates haploid gametes from diploid parental cells in sexually reproducing organisms. Meiosis is essential for the maintenance of a stable chromosome count through successive generations. Failure would result in zygotes with an abnormal number of chromosomes, which is usually lethal to the cell. During meiosis, homologous chromosomes are paired together, and meiotic recombination plays a critical role in this process. Physical connection between homologous chromosomes is essential for their accurate segregation, and the ability of the cell to pair homologous chromosomes during meiosis is remarkable. Multiple DNA double-strand breaks are introduced across the entire genome; the DNA strands with these breaks are then digested by exonucleases to expose single-stranded regions. The duplex region homologous to the exposed single-stranded DNA is then searched for across the genome; this is compli- cated by the fact that interhomolog recombination is preferred over recombination between sister chromat- ids. Many of the mechanisms that underlie the faithful segregation of chromosomes during meiosis and the process of packaging and propagating the genomic DNA to the offspring during the postmeiotic events are still poorly understood. Our minireview series starts with the topic of the recognition of homologous chromosomes. Although meiotic recombination is critical for the accurate pair- ing of homologous chromosomes, this process also involves the global alignment of homologous chromo- somes. The possible existence of chromosome-specific identifiers that can recognize homology without directly comparing DNA sequences is discussed. The second minireview describes the importance of meiotic recombination in meiosis, and the current understanding of this process and its control mecha- nisms. Imperfections in meiotic recombination have been linked with de novo germline mutations, abnor- mal gametes, and infertility. Unexpectedly, this impor- tant process shows remarkable flexibility in both the number and distribution of recombination events along the entire genome. A special emphasis is placed on the potential role of histone modifications in the distribu- tion of meiotic recombination sites. The third topic in this minireview series is the Dmc1 recombinase, which is one of the key players in meiotic recombination. Recent biochemical and structural studies of Dmc1 and its homologs have revealed unprec- edented details of how Dmc1 may catalyze DNA strand exchange. As Dmc1 and its homolog, Rad51, both participate in meiotic recombination, these two recom- binases are expected to have different roles, and thus to have intrinsic structural and biochemical differences. Studies are underway to decipher these differences. The last minireview focuses on the structure of the haploid chromosome during the postmeiotic phases of spermatogenesis. Genome-wide compaction and reorga- nization of the haploid chromosome is known to occur after meiosis is completed. However, virtually nothing is known about the mechanisms underlying the genome- wide replacements of histones with the histone variants and nonhistone DNA-packaging basic proteins that occur during the postmeiotic phases of spermatogenesis. The minireview focuses on the possible roles of histone variants and modifications in this dynamic event. We hope that these minireviews will contribute to the field of meiosis, as well as that of chromatin dynamics. Wataru Kagawa is an Assistant Professor in the Graduate School of Advanced Science and Engineering at Waseda Uni- versity. He received his PhD degree from the Department of Biochemistry and Biophysics at the University of Tokyo. He has performed biochemical and X-ray crystallographic studies on homologous recombination factors, RAD52 and DMC1. His primary interest is in understanding the relationship between the three-dimensional structures of macromolecules and their functions in DNA repair, replication, and recombination, using X-ray crystallography as the main tool. Hitoshi Kurumizaka is a Professor in the Graduate School of Advanced Science and Engineering at Waseda University. He received his PhD degree from Saitama University under the supervision of Dr Takehiko Shibata. He studied the molecular mechanisms of homologous recombination. Dr Kurumizaka joined Dr Alan P. Wolffe’s laboratory at the National Institutes of Health, USA, as a postdoctoral fellow, where he investigated the roles of chromatin structure in transcription. He later joined the RIKEN Institute as a research scientist. His current research focuses on the mecha- nisms of homologous recombination in the context of chromosomal architecture. doi:10.1111/j.1742-4658.2009.07500.x 564 FEBS Journal 277 (2010) 564 ª 2009 The Authors Journal compilation ª 2009 FEBS . MINIREVIEW SERIES Dynamics in the transmission of genetic information: from meiosis to postmeiotic events Wataru Kagawa and Hitoshi Kurumizaka Graduate School of Advanced Science and Engineering,. packaging and propagating the genomic DNA to the offspring during the postmeiotic events are still poorly understood. Our minireview series starts with the topic of the recognition of homologous chromosomes about the mechanisms underlying the genome- wide replacements of histones with the histone variants and nonhistone DNA-packaging basic proteins that occur during the postmeiotic phases of spermatogenesis. The