Systematic alteration of the nucleotide sequence preceding the translation initiation codon and the effects on bacterial expression of the cloned SV40 small-t antigen gene.

In the preceding paper (Derom et al., 1981) we described the cloning in bacterial plasmids of the simian virus 40 (SV40) small-t antigen gene under transcriptional control of the bacteriophage lambda pL promoter. Systematic variation of the distance and/or nucleotide sequence between the Shine-Dalgarno ribosome interaction sequence and the small-t translation initiation codon leads to considerable differences in production of small-t by the different plasmids. Secondary structure models derived for the different mRNAs confirm our previous conclusions about the requirement first for an accessible start codon and second for an accessible ribosome interaction site for efficient translation initiation. Secondary structure models for mRNAs from plasmids containing the small-t gene under control of the lac promoter are in agreement with these conclusions.