An analysis of sequences stimulating frameshifting in the decoding of gene 10 of bacteriophage T7

The signals necessary for the translational frameshift in the gene 10 message of bacteriophage T7 include the previously identified frameshift site and the 3' non-coding region, over 200 bases downstream. The functional components of the frameshift site are identified in this study and show that the site most probably operates by the retroviral type two site mechanism. However, the base pairing requirements for the first tRNA are much more relaxed after the slip than is seen in other examples. The element at the 3' end of the gene, also necessary for frameshifting, is examined but only the extreme 5' side of the transcriptional terminator stem-loop structure in the 3' non-coding region seems to be required. No simple secondary structural model can explain the involvement of this sequence. The T7 frameshift site can be replaced with either a T3 site or a E. coli dnaX site. Both show higher levels of frameshifting than with the T7 site.