Coding strategy differences between constant and variable segments of immunoglobulin genes

Correlation between molecular clock ticking, codon usage fidelity of DNA repair, chromosome banding and chromatin compactness in germline cells

The vertebrate genome is built of long DNA regions, relatively homogeneous in GC content, which likely correspond to bands on stained chromosomes. Large differences in composition have been found among DNA regions belonging to the same genome. They are paralleled by differences in codon usage in genes differently localized. The hypothesis presented here asserts that these differences in composition are caused by different mutational bias of alpha and beta DNA polymerases, these polymerases being involved to different extents in the repair of DNA lesions in compact and relaxed chromatin, respectively, in germline cells.

Translation rate modification by preferential codon usage: intragenic position effects

We present a model for calculating the protein production rate as a function of the translation rate. The model takes into account that the elongation rate along an mRNA molecule is non-uniform as a result of different tRNA availabilities for different codons. Initiation of ribosomes on an mRNA is normally the rate-limiting step in the translation process, and blocking of the initiation site can be avoided if the codons closest to this site allow fast translation by the ribosome. Hence, different selective forces may act on the choice of synonymous codons in the initiation region than elsewhere on a given mRNA. We show that the elongation rate along the whole mRNA influences the production rate of abundant proteins, whereas only the elongation rate in the initiation region is of importance for the production rate of rare proteins. We also present an analysis of the codon distribution along known mRNAs coding for abundant and rare proteins.