title: RNA relics and origin of life.
abstract: A number of small RNA sequences, located in different non-coding sequences and highly preserved across the tree of life, have been suggested to be molecular fossils, of ancient (and possibly primordial) origin. On the other hand, recent years have revealed the existence of ubiquitous roles for small RNA sequences in modern organisms, in functions ranging from cell regulation to antiviral activity. We propose that a single thread can be followed from the beginning of life in RNA structures selected only for stability reasons through the RNA relics and up to the current coevolution of RNA sequences; such an understanding would shed light both on the history and on the present development of the RNA machinery and interactions. After presenting the evidence (by comparing their sequences) that points toward a common thread, we discuss a scenario of genome coevolution (with emphasis on viral infectious processes) and finally propose a plan for the reevaluation of the stereochemical theory of the genetic code; we claim that it may still be relevant, and not only for understanding the origin of life, but also for a comprehensive picture of regulation in present-day cells.
authors.affiliation: University Joseph Fourier of Grenoble, TIMC-IMAG UMR UJF/CNRS 5525, Faculty of Medicine, 38700 La Tronche, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Demongeot
authors.affiliation: University Joseph Fourier of Grenoble, TIMC-IMAG UMR UJF/CNRS 5525, Faculty of Medicine, 38700 La Tronche, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Glade
authors.affiliation: Departamento de Informática, Universidad Federico Santa María, Casilla 110-V, Valparaíso, Chile.
authors.forename: Andrés
authors.initials: A
authors.lastname: Moreira
authors.affiliation: Département de Chimie Moléculaire, UMR CNRS 5250, Université Joseph Fourier, 301 rue de la chimie, BP 53, 38041 Grenoble Cedex 9, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Vial
mesh_terms: D005075:Biological Evolution; D004267:DNA Viruses / Q000235:genetics; D005815:Genetic Code; D016679:Genome, Viral; D035683:MicroRNAs / Q000737:chemistry / Q000378:metabolism; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D000069497:Origin of Life; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D012328:RNA Viruses / Q000235:genetics; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism
chemical_list: D035683:MicroRNAs; D012313:RNA; D012343:RNA, Transfer