Sm/Lsm genes provide a glimpse into the early evolution of the spliceosome.

TitleSm/Lsm genes provide a glimpse into the early evolution of the spliceosome.
Publication TypeJournal Article
Year of Publication2009
AuthorsVeretnik S, Wills C, Youkharibache P, Valas RE, Bourne PE
JournalPLoS Comput Biol
Date Published2009 Mar
KeywordsBase Sequence, Evolution, Molecular, Genetic Variation, Models, Genetic, Molecular Sequence Data, Ribonucleoproteins, Small Nuclear, Sequence Analysis, DNA, Species Specificity, Spliceosomes

The spliceosome, a sophisticated molecular machine involved in the removal of intervening sequences from the coding sections of eukaryotic genes, appeared and subsequently evolved rapidly during the early stages of eukaryotic evolution. The last eukaryotic common ancestor (LECA) had both complex spliceosomal machinery and some spliceosomal introns, yet little is known about the early stages of evolution of the spliceosomal apparatus. The Sm/Lsm family of proteins has been suggested as one of the earliest components of the emerging spliceosome and hence provides a first in-depth glimpse into the evolving spliceosomal apparatus. An analysis of 335 Sm and Sm-like genes from 80 species across all three kingdoms of life reveals two significant observations. First, the eukaryotic Sm/Lsm family underwent two rapid waves of duplication with subsequent divergence resulting in 14 distinct genes. Each wave resulted in a more sophisticated spliceosome, reflecting a possible jump in the complexity of the evolving eukaryotic cell. Second, an unusually high degree of conservation in intron positions is observed within individual orthologous Sm/Lsm genes and between some of the Sm/Lsm paralogs. This suggests that functional spliceosomal introns existed before the emergence of the complete Sm/Lsm family of proteins; hence, spliceosomal machinery with considerably fewer components than today's spliceosome was already functional.

PubMed URL
Alternate TitlePLoS Comput. Biol.
PubMed ID19282982