UNUSUAL EFFECT OF CLUSTERS OF RARE ARGININE (AGG) CODONS ON THE EXPRESSION OF HUMAN INTERFERON ALPHA-1 GENE IN ESCHERICHIA-COLI

The human interferon (hIFN alpha(1)) gene contains 11 arginine (Arg) c odons AGG or AGA, which are extremely rare for bacteria, four of which are organized in tandems. The two AGG tandems (corresponding to Arg(1 2) Arg(13) and Arg(163) Arg(164)) are known to inhibit the translation of hIFIV alpha(1) mRNA and therefore they are considered to be respon sible for the poor expression of hIFN alpha(1) gene in bacterial cells . To study the effect of these two tandems on the expression of hIFN a lpha(1), in E. coli, four new gene variants were designed to contain p referential Arg codons (CGT) substituted for the rare AGG codons in ei ther the first, the second or both AGG tandems. We found that, whereas the yield of hIFN alpha(1) protein per cell remained unchanged, the l evel of hIFN alpha(1) mRNA decreased gradually (by a factor of two) wi th the consecutive substitution of the first, second and both AGG tand ems. These results indicated, first, that the AGG clusters might have a stabilizing effect on the mRNA, and second, that mRNAs devoid of suc h clusters were translated at a higher rate in vivo. The protein produ cts of the four genes (having the same amino acid sequence) showed dif ferent specific antiviral activity. The most active was the product of gene hIFN alpha(1(c)) in which the second AGG tandem (corresponding t b Arg(163), Arg(164)) was preserved while the least active was the pro tein of gene hIFN alpha(1(d)) (devoid of both AGG clusters). The role of the AGG tandems in folding of the gene product is discussed. (C) 19 97 Published by Elsevier Science Ltd.