Polyamines enhance the efficiency of tRNA-mediated readthrough of amber and UGA termination codons in a yeast cell-free system.

The effects of polyamines (spermidine and putrescine) on yeast suppressor tRNA-mediated readthrough of amber and UGA termination codons, in a homologous cell-free system, was examined. The efficiency of readthrough in a [psi+] lysate, mediated by exogenous suppressor tRNA, was significantly increased by polyamines as was the efficiency of endogenous UGA readthrough. The addition of polyamines, in the absence of exogenous suppressor tRNA, did not induce amber or ochre readthrough, nor could polyamines restore efficient termination readthrough in [psi(-)] lysates. It is concluded that polyamines interact with tRNA to increase the strength and specificity of the codon: anticodon interaction.