Saccharomyces cerevisiae mRNA populations of different intrinsic stability in unstressed and heat shocked cells display almost constant m 7GpppA:m 7GpppG 5′-cap structure ratios

Abstract

The half-lives of mRNAs in yeast vary from about 1 to over 100 min. While mRNA stabilities must strongly influence overall gene expression in this organism, very little is known about how they are determined. Labellings of yeast cells were conducted to investigate whether the 5′-cap structures of yeast mRNAs might influence their stability. Variation of the pulse-labelling period from 7.5 min to 120 min did not have any major influence on the relative labelling of m 7GpppA (A cap) and m 7GpppG (G cap) in total polyadenylated RNA. Whether an mRNA has the A cap or the G cap does not therefore have a marked effect on its stability. During the heat shock response the relative labelling of A caps to G caps in total polyadenylated RNA also does not fluctuate appreciably. This indicates that cap structure alone does not determine the destabilisation of non-heat shock mRNAs and stabilisation of heat shock mRNAs during this stress response.