Termination-reinitiation occurs in the translation of mammalian cell mRNAs.

摘要: Many examples of internal translation initiation in eucaryotes have accumulated recent years. In many cases terminators upstream reading frames precede the site, suggesting that translational reinitiation may be a mechanism for at AUGs. To test this idea, series recombinants was constructed mammalian expression vector pSV2. Each contained dicistronic transcription unit comprising coding sequence mouse dihydrofolate reductase (DHFR) followed by gene xanthine-guanine phosphoribosyl transferase (XGPRT) from Escherichia coli. Various versions pSV2dhfr-gpt recombinant plasmid altered location which DHFR frame terminated relative to XGPRT codon and demonstrated is critical factor activity transfected Cos-1 cells. Thus, when or very short distance downstream initiator AUG, substantial levels were observed. When 50 nucleotides beyond initiator, reduced about twofold. However, sequences fused in-frame so ribosomes initiated AUG did not terminate until they encountered terminator, production abolished. This dependence on position consistent with hypothesis are capable reinitiation.