Molecular evolutionary study of RNA viral genes.

本研究项目的目的是从分子进化的角度阐明RNA病毒的进化特征。特别是，我们研究了RNA病毒（如人类免疫缺陷病毒（HIV）和肿瘤病毒）的核苷酸取代率。我们发现，这些典型的逆转录病毒的替代率是每年每个位点10^的数量级<-3>。这些速率是包括核基因和线粒体基因在内的真核基因的10^6倍。虽然人类肝炎B病毒（HBV）不是RNA病毒，但我们也检查了HBV的核苷酸替换率。这是因为HBV具有逆转录酶，这是逆转录病毒特有的聚合酶。HBV的替代率估计为每年每个站点10^的数量级<-5>。以人T细胞白血病病毒Ⅰ型和Ⅱ型（HTLV -Ⅰ/Ⅱ）为例，我们发现HTLV-Ⅰ/Ⅱ的核苷酸替换率远高于真核病毒，但低于逆转录病毒，并利用核苷酸替换数构建了HTLV-Ⅰ/Ⅱ的系统发育树。因此，我们得出结论，在这项研究中检查的病毒显示出“不依赖宿主的进化。"

The aim of this research project was to clarify the evolutionary features of RNA viruses from the viewpoint of molecular evolution. In particular, we studied the rate of nucleotide substitutions of RNA viruses such as human immunodeficiency viruses (HIV) and oncoviruses. We found that the substitution rates of these typical retroviruses are the order of 10^<-3> per site per year. These rates are 10^6 times greater than those of eukaryotic genes including nuclear and mitochondrial genes. Although human hepatitis B virus (HBV) is not a RNA virus, we also examined the rate of nucleotide substitution of HBV. This is because HBV possesses reverse transcriptase that is a polymerase unique to retroviruses. The substitution rate of HBV is estimated to be the order of 10^<-5> per site per year. In the case of human T cell leukemia viruses types I and II (HTLV - I / II), we suggested that the substitution rate is much higher than those of eukaryotic genes but lower than those of retroviruses.Using the numbers of nucleotide substitutions, we constructed the phylogenetic trees for the above-mentioned viruses. As the result, we concluded that the viruses examined in this research show "host-independent evolution."