Domains in human interferon alpha-1 gene containing tandems of arginine codons AGG play the role of translational initiators in E. coli.

The AGG and AGA are the least used arginine codons in E. coli but they are the most preferable ones in eukaryotes. The low expression of some eucaryotic genes (such as human alpha-1 interferon gene) which contain clusters of AGG codons is explained either by the limited pool of the tRNA(AGG) (Varenne and Lazdunski, 1986) or by the competition of these clusters with the Shine-Dalgarno (SD) sequence (Ivanov et al., 1992). The aim of the present study is to demonstrate the in vivo capacity of AGG tandems to bind to bacterial ribosomes. The two tandems of AGG codons (Arg12 Arg13 and Arg163 Arg164) of hIF alpha 1 with their surrounding nucleotides were cloned in a bacterial expression plasmid containing a strong promoter and a reporter gene (chloramphenicol acetyltransferase, CAT) devoid of a ribosome binding site. The results obtained showed that both AGG tandems initiated translation of the CAT mRNA with an efficiency equal to that of the consensus SD sequence and several fold higher than the native SD sequence of the CAT gene.