SPERMIDINE DEFICIENCY INCREASES -CEREVISIAE(1 RIBOSOMAL FRAMESHIFTINGEFFICIENCY AND INHIBITS TY1 RETROTRANSPOSITION IN SACCHAROMYCES)

Polyamines have been implicated in nucleic acid-related functions and in protein biosynthesis. RNA sequences that specifically direct riboso mes to shift reading frame in the -1 and +1 directions may be used to probe the mechanisms controlling translational fidelity. We examined t he effects of spermidine on translational fidelity by an in vivo assay in which changes in beta-galactosidase activity are dependent on yeas t retrovirus Ty +1 and yeast double-stranded RNA virus L-A -1 ribosoma l frameshifting signals. In spe2DELTA mutants of Saccharomyces cerevis iae, which cannot make spermidine as a result of a deletion in the SPE 2 gene, there is a marked elevation in +1 but no change in -1 ribosoma l frameshifting. The increase in +1 ribosomal frameshifting efficiency is accompanied by a striking decrease in Ty1 retrotransposition.