For the purpose of elucidating the biological information included in the sugar chains of glycoconjugates, and of using them for the understanding of biology, glycobiology has launched. In contrast to nucleic acids and proteins, sugar chains of many different structures can be formed by using a small number of monosaccharide units. Finding of a series of structural rules in the sugar chains enabled us to consider the functions of sugar chains on their structural basis. Recent finding of a novel group of sugar chains in dystroglycan further expanded this novel scientific field of molecular biology.
Dolphins have bio-sonar ability called echoiocation. Clicks, echolocation signals, provide various biological information, such as, species, target range and acoustical survey effort of dolphins. Acoustical measurement is anewly developed method to observe underwater behavior of vocalizing animals.
Re-initiation of DNA replication from a newly replicated origin has to be suppressed so that DNA replication couples with cell division. In this review, I show our original model for the suppression, DNA replication-dependent inactivation of initiator protein for DNA replication. I also describe recent studies suggesting that membrane acidic phospholipids are involved in the regulation of initiation of DNA replication in cells.
Genetic material suffers various spontaneous or environmental damages, among which DNA double-strand breaks (DSBs) are fatal to the cell since they bring to the loss of genetic information. Cells provide with two strategies to repair DSBs. One is through homologous recombination and the other through an end-to-end joining reaction. The former process is more accurate. RAD52 group genes of budding yeast are involved in these DSB repair processes. They are classified into two subgroups: one is composed of RAD51, 52, 54, 55 and 57 (RAD51 subgroup), which are involved in homologous recombination, and the other MRE11, RAD50 and XRS2 (MRE11 subgroup), which are involved in end-to-end joining. The DSB repair system is required for the proper segregation of homologous chromosomes in the reductional division of meiosis. Meiotic recombination is initiated with the formation of DSBs, the ends of which are processed and provided for homology search. Two subgroup genes work at two distinct steps: MRE11 subgroup at DSB formation and RAD51 subgroup at homology search, respectively. In addition, other meiosis specific proteins are also required for initiation and completion of meiotic recombination, some of which are components of synaptonemal complex. This review focuses on recent advances in the mechanism of DSB repair and its involvement in meiosis.