Analysis of effects of tRNA:message stability on frameshift frequency at theEscherichia coliRF2 programmed frameshift site

Abstract

The codon that is in-frame prior to +1 frameshiftlng at the E.coll prfB (RF2 gene) frameshlft site Is randomized to create thirty-two variants. These alleles vary 1000-fold in frameshift-dependent expression in fusions to lacZ. Frameshiftlng is more frequent at sites where the In-frame codon ends In urldine, as if third position wobble pairs to message urldine facilitate slippage Into the +1 frame. Consistent with other studies of programmed frameshlft sites, efficient frameshlfting depends on stable message:tRNA base pairs after rephaslng. For complexes with mispalrs, frameshift frequency depends on the nature, number, and position of mispairs. Central purine:purine mispalrs are especially inhibitory. Relative stabilities of +1 rephased complexes are estimated from published data on the stabilities of tRNA:tRNA complexes. Stability correlates with frameshifting over its entire range, which suggests that stability is an important determinant of the probability of translation of the rephased complex.