MBE Advance Access originally published online on August 22, 2006
Molecular Biology and Evolution 2006 23(11):2214-2219; doi:10.1093/molbev/msl096
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© 2006 The Authors
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Research Articles |
UV-Targeted Dinucleotides Are Not Depleted in Light-Exposed Prokaryotic Genomes
Laboratoire de Biométrie et Biologie Évolutive (UMR 5558); Centre National de la Recherche Scientifique (CNRS); Univ. Lyon 1, 43 bd 11. nov, 69622, Villeurbanne, Cedex, France; and HELIX, Unité de recherche, Institut National de Recherche en Informatique et en Automatique (INRIA)
E-mail: palmeira{at}biomserv.univ-lyon1.fr.
We have investigated the hypothesis that pyrimidine dinucleotides are avoided in light-exposed genomes as the result of selective pressure due to high ultraviolet (UV) exposure. The main damage to DNA produced by UV radiation is known to be the formation of pyrimidine photoproducts: it is estimated that about 10 dimers per minute are formed in an Escherichia coli chromosome exposed to the UV light in direct overhead sunlight at sea level. It is also known that on an E. coli chromosome exposed to UVb wavelengths (290320 nm), pyrimidine photoproducts are formed in the following proportions: 59% TpT, 7% CpC, and 34% CpT plus TpC. We have analyzed all available complete prokaryotic genomes and the model organism Prochlorococcus marinus and have found that pyrimidine dinucleotides are not systematically avoided. This suggests that prokaryotes must have sufficiently effective protection and repair systems for UV exposure to not affect their dinucleotide composition.
Key Words: G + C content dinucleotide content ultraviolet radiation aerobiosis Prochlorococcus marinus