A TRANSIENT GCN4 MESSENGER-RNA DESTABILIZATION FOLLOWS GCN4 TRANSLATIONAL DEREPRESSION

Studies based on experimental strategies that utilized either inhibito rs or structural alterations point to the existence of an inverse rela tionship between translation and stability of a given mRNA. In this st udy we have investigated the potential link between translation and st ability of the yeast GCN4 mRNA whose translational rates change with r espect to amino acid availability. We observed that under conditions f avoring its translation, the steady state levels of the GCN4 mRNA were decreased, but this was not due to a measurable alternation in its de cay rate. We have demonstrated that an extensive destabilization of th is message is intimately coupled with its increased access to heavy po lysomes, which occurs transiently in the process of translational dere pression. This transient change in the stability is what readjusts the steady state levels of the GCN4 mRNA. This study demonstrates in vivo the existence of a mechanism of mRNA degradation that is coupled with the process of translation.