Structural and contextual features of mRNAs encoding high- and low-abundant proteins in eukaryotic cells were compared. These two mRNA groups were found to differ in their 5' untranslated regions (5'-UTR): statistically, the leader sequences of the low-expression mRNAs are longer, their guanine plus cytosine content is higher, and they form more stable secondary structures than the leaders of the high-expression mRNAs. Analysis of the translational properties of the mRNAs of the low-expression genes demonstrated weaker context of the translation start codon and more frequent occurrence of AUGs within their 5'UTRs compared with the high-expression mRNAs. Apart from the differences in the 5'UTRs, high-expression mRNAs more frequently contain strong termination signals. These structural features of the of low- and high-expression mRNAs may contribute to the different translational efficiency and abundance of their protein products. It seems likely that optimal structural features of mRNA are essential to maintain the high expression level of eukaryotic genes whereas small amounts of regulatory polypeptides may be efficiently produced from low-active mRNAs. Besides, low mRNA translational efficiency may be important to make the control of expression of regulatory genes more stringent to prevent overproduction.

Significant differences between the structural features of 5'UTR mRNA may be used to discriminate between the high and low expression eukaryotic genes. We designed a version of computer program (http://wwwmgs.bionet.nsc.ru/programs/acts2/dicot.htm) allowing to predict the expression level of genes of dicot plants. This program may also be used in genetic engineering to predict the expression level of foreign genes in transgenic dicot plants.