THE DESTABILIZING ELEMENTS IN THE CODING REGION OF C-FOS MESSENGER-RNA ARE RECOGNIZED AS RNA

The protein-coding region of the c-fos proto-oncogene transcript conta ins elements that direct the rapid deadenylation and decay of this mRN A in mammalian cells. The function of these coding region instability determinants requires movement of ribosomes across mRNAs containing th em. Three types of mechanisms could account for this translational req uirement. Two of these possibilities, (i) that rapid mRNA decay might be mediated by the nascent polypeptide chain and (ii) that it might re sult from an unusual codon usage, have experimental precedent. Here, w e present evidence that the destabilizing elements in the c-fos coding region are not recognized in either of these two ways. Instead, the a bility of the c-fos coding region to function as a potent mRNA destabi lizer when translated in the +1 reading frame indicates that the signa ls for rapid deadenylation and decay reside in the sequence or structu re of the RNA comprising this c-fos domain.