Selective forces for the origin of spliceosomes
- 306 Downloads
It has been proposed that eukaryotic spliceosomes evolved from bacterial group II introns via constructive neutral changes. However, a more likely interpretation is that spliceosomes and group II introns share a common undefined RNA ancestor—a proto-spliceosome. Although, the constructive neutral evolution may have probably played some roles in the development of complexity including the evolution of modern spliceosomes, in fact, the origin, losses and the retention of spliceosomes can be explained straight-forwardly mainly by positive and negative selection: (1) proto-spliceosomes evolved in the RNA world as a mechanism to excise functional RNAs from an RNA genome and to join non-coding information (ancestral to exons) possibly designed to be degraded. (2) The complexity of proto-spliceosomes increased with the invention of protein synthesis in the RNP world and they were adopted for (a) the addition of translation signal to RNAs via trans-splicing, and for (b) the exon-shuffling such as to join together exons coding separate protein domains, to translate them as a single unit and thus to facilitate the molecular interaction of protein domains needed to be assembled to functional catalytic complexes. (3) Finally, the spliceosomes were adopted for cis-splicing of (mainly) non-coding information (contemporary introns) to yield translatable mRNAs. (4) Spliceosome-negative organisms (i.e., prokaryotes) have been selected in the DNA–protein world to save a lot of energy. (5) Spliceosome-positive organisms (i.e., eukaryotes) have been selected, because they have been completely spliceosome-dependent.
KeywordsConstructive neutral evolution Ribosome RNA world Selection Trans-splicing
Constructive neutral evolution
Last eukaryotic common ancestor
Last universal common ancestor
This work was supported by a grant VEGA 1/0416/09 from the Ministry of Education of the Slovak Republic to J. K., and is the result of the project implementation: “the improvement of centre of excellence for exploitation of informational biomacromolecules in disease prevention and improvement of quality of life,” ITMS 26240120027, supported by the Research and Development Operational Programme funded by the ERDF.
- Cech TR (2011) The RNA world in context. Cold Spring Harb Perspect Biol. doi: 10.1101/cshperspect.a006742
- Forterre P (1995) Thermoreduction, a hypothesis for the origin of prokaryotes. C R Acad Sci Paris Life Sci 318:414–422Google Scholar
- Gilbert W, de Souza SJ (1999) Introns and the RNA world. In: Gesteland RF, Cech TR, Atkins RF (eds) The RNA world, the nature of modern RNA suggests a prebiotic RNA World, vol. 37, 2nd edn. CSHL Press, New York, pp 221–231Google Scholar
- Lukeš J, Leander BS, Keeling PJ (2009) Cascades of convergent evolution: the corresponding evolutionary histories of euglenozoans and dinoflagellates. Proc Natl Acad Sci USA 106:9963–9970Google Scholar
- Lynch M (2007) The origins of genome architecture. Sinauer, SunderlandGoogle Scholar