内含子地起源与进化牛登科北京师范大学生命科学学院http.pptVIP

* * * * * 内含子的起源与进化 牛登科 北京师范大学生命科学学院 /tabid/88/Default.aspx dkniu@, dengkeniu@What is an intron? Categories of introns Spliceosomal introns: Major intron, U2-dependent, GT……AG; Minor intron, U12-dependent, AT……AC. Most of the studies on intron evolution are focused on spliceosomal introns. And in most papers, without further annotation, the term intron means spliceosomal introns. Self splicing introns: Group I and Group II introns tRNA and/or archaeal introns The pervasiveness and abundance of introns Except a few nucleomorph genomes(1), all nuclear genomes contains introns. Human has 8 introns/gene; 45% to 55% of the human genome are introns. The dinoflagellate Symbiodinium minutum has 18.6 introns/gene (2). There are also intron-poor genomes and intronless genes in intron-rich genomes. 1. Shoguchi E, et al: Curr Biol 2013, 23: 1399-1408. 2. Lane CE, et al. PNAS 104: 19908-19913. Secondary endosymbiosis---Nucleomorph John MA 2007. Nucleomorph genomes: structure, function, origin and evolution. BioEssays 29: 392-402. Origin of introns One exon --- one function unit, building blocks of genes since the origin of genes Introns have been found in almost all eukaryotic species, but not in prokaryotes (eubacteria and archaebacteria) Intron early theory, Intron late theory. Origin of introns 1. Go, M. (1983) Proc. Natl. Acad. Sci. USA 80, 1964-1968. 2. Perler, F., et al. (1980) Cell 20, 555-566. 3. Sudhof, T. C., et al. (1985) Science 228, 815-822. 4. Sudhof, T. C., et al. (1985) Science 228, 893-895. 5. Rogers, J. (1985) Nature 315, 458-459. 6. Gilbert, W. (1985) Science 228, 823-824. 7. Henkel, B., et al. (1992) Eur. J. Biochem. 209, 321-328. Origin of introns The occurrence of shared sequences encoded by discrete exons in the LDL receptor gene provides strong evidence in support of Gilberts original hypothesis that introns facilitate the evolution of apparently diverse genes by allowing recruitment of exons encoding functional domains. But far from demons