RECENT TOPICS IN RNA RESEARCH IN JAPAN
YOSHIRO SHIMURA
RNA was classically thought to function in gene expression as the carrier of genetic messages and the scaffold necessary for protein synthesis. Recently, it has been clearly shown that RNA plays important roles in many other biological functions. This talk will briefly survey the recent highlights in RNA research in Japan.
Yamamoto et al (The Univ. of Tokyo) have demonstrated that specific RNA and its binding protein participate in meiotic division of fission yeast. The complex of the protein and the RNA migrate from cytoplasm to nucleus, thereby initiating the first meiotic division. Nakamura et al (The Univ. of Tokyo) have finally solved the long-standing problem how the stop codons are recognized by the specific releasing factors in the terminations of protein synthesis. They showed that the molecular structure of the releasing factors mimics tRNA and consequently the factors are possible to interact specifically with the respective stop codons at the A site on the ribosome. Ishikawa et al (Tokyo Inst. of Technology) posed a question why we have linear chromosomes with paying extra costs such as telomeres and telomerase. They have recently isolated fisson yeast mutants having circular chromosomes. These mutants cannot undergo sexual reproduction, thereby indicating that telomeres are essential for completion of sexual reproduction. Taira et al (The Univ. of Tokyo) designed a novel allosterically controllable ribozyme (designated maxizyme) with exceptional activity and specificity in vitro and in vivo. The maxizyme could specifically disrupt chimeric fusion mRNA from chronic myelogenous leukemia caused by reciprocal chromosomal translocations. Yokoyama et al (The Univ. of Tokyo) have determined the crystal structure of the complex between the two tandemly-arranged RNA binding domains of Sex-lethal protein of Drosophila melanogaster and a 12-nucleotides, single-stranded RNA derived from the transformer polypyrimidine tract. The negative control of alternative splicing of transformer pre-mRNA by Sex-lethal protein was previously clarified in vivo by Shimura et al (Kyoto Univ.). Yokoyama et al have also determined the crystal structure of HuC protein and the AU rich element. HuC protein has been shown to be neuron specific and to induce neuronal differentiation by Sakamoto et al (Kobe Univ.). Finally, the recent foundation of the RNA Society of Japan will be mentioned. The foundation became possible by enthusiastic efforts of young scientists in the field.