Eukaryotic ribosomes can recognize preproinsulin initiation codons irrespective of their position relative to the 5′ end of mRNA

Lomedico, Peter T.; McAndrew, Stephen J.

doi:10.1038/299221a0

Cited by 77 publications

(27 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We therefore suggest that translation of the wildtype src message produces a nine-amino acid polypeptide in addition to the 60,000-dalton src protein. There are several examples of single mRNAs that appear to have more than one functional site of initiation (2,16,21,22), and two recent reports support the idea that termination codons can have a profound influence on initiation (19a, 20a).…”

Section: Resultsmentioning

confidence: 99%

Mutation of a termination codon affects src initiation.

Hughes¹,

Mellström²,

Kosik³

et al. 1984

Mol. Cell. Biol.

View full text Add to dashboard Cite

The four Rous sarcoma virus messages gag, gag-pol, env, and src all derive from a fuli-length RNA precursor. All four messages contain the same 5' leader segment. Three of the messages, gag, gag-pol, and env, use an AUG present in this leader to initiate translation. The src AUG initiation codon lies 3' of the leader segment, 90 bases downstream of the gag initiation codon in the spliced src message. However, in the spliced src message a UGA termination codon lies between the gag AUG and the src AUG. All three codons are in the same reading frame. By using oligonucleotide-directed mutagenesis, the UGA termination codon has been converted to CGA. Cells infected with the mutant (called 1057 CGA) were spindle shaped, distinct from the rounded shape of cells infected with the parental Rous sarcoma virus. The mutant virus initiates src ranslation at the gag AUG, producing a 63,000-dalton src protein. We suggest that the wild-type src message produces two polypeptides, a very small (nine-amino acid) peptide that is initiated at the gag AUG and the 60,000-dalton src protein that is initiated at the src AUG.Rous sarcoma virus (RSV) is apparently transcribed into a single RNA species beginning at the left end of the R sequence in the left-hand long terminal repeat and terminating at the right end of the R sequence in the right-hand long terminal repeat. This transcript constitutes genomic RNA and serves as the precursor for RSV messenger RNAs. Four messenger RNAs are known: gag mRNA, which is apparently unspliced and is thought to be identical to genomic RNA; gag-pol mRNA, which may have a small region near the gag-pol junction removed by RNA splicing; env mRNA, which has most of gag and pol removed by splicing; and src mRNA, which has most of gag, pol, and env removed by splicing (30; Fig.

show abstract

Section: Resultsmentioning

confidence: 99%

Mutation of a termination codon affects src initiation.

Hughes¹,

Mellström²,

Kosik³

et al. 1984

Mol. Cell. Biol.

View full text Add to dashboard Cite

show abstract

“…(Note that, although p255/15A has the canonical A in position -3, it differs in everyotherposition from the consensus sequence for eucaryotic initiation sites.) An alternative explanation, advocated by Lomedico and McAndrew (12), is that some ribosomes can bind directly to the preproinsulin start site without traversing the upstream region. In that case residual translation of proinsulin would persist no matter what sort of barrier were placed upstream.…”

Section: Insertion and Mutagenesis Of A Synthetic Atg-containing Oligmentioning

confidence: 99%

Selection of initiation sites by eucaryotic ribosomes: effect of inserting AUG triplets upstream from the coding sequence for preproinsulin

1984

View full text Add to dashboard Cite

Recombinant plasmids that direct synthesis of rat preproinsulin under the direction of the SV40 early promoter have been used to probe the mechanism of initiation of translation. Insertion of an upstream AUG triplet that was outof-frame with respect to the coding sequence for preproinsulin red iced the yield of proinsulin, in keeping with the predictions of the scanning model. The extent to which an upstream AUG codon interfered depended on sequences surrounding the AUG triplet; with two constructs (p255/20 and C2) the 5'-proximal AUG codon constituted an absolute barrier: there was no initiation at the downstream start site for preproinsulin. With two other constructs (p255/9, p255/21), however, proinsulin was made despite the presence of an upstream, out-of-frame AUG codon in a favorable context for initiation. In those cases the reading frame set by the first AUG triplet was short, terminating before the start of the preproinsulin coding sequence. The interpretation that ribosomes initiate at the first AUG, terminate, and then reinitiate at the AUG that directly precedes the preproinsulin coding sequence was tested by introducing a point mutation that eliminated the terminator codon: the resulting mutant made no proinsulin.

show abstract

“…Many naturally occurring cellular (14,44,55,58) and viral mRNAs (5,7,10,11,17,19,30,31,53,57) are now known to initiate translation at internal AUGs. Moreover, internal initiation has been demonstrated in molecules constructed artificially by recombinant DNA methods (29,38,50,52).…”

mentioning

confidence: 99%

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

Peabody¹,

Berg²

1986

Mol. Cell. Biol.

226

131

View full text Add to dashboard Cite

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

show abstract

Eukaryotic ribosomes can recognize preproinsulin initiation codons irrespective of their position relative to the 5′ end of mRNA

Cited by 77 publications

References 27 publications

Mutation of a termination codon affects src initiation.

Mutation of a termination codon affects src initiation.

Selection of initiation sites by eucaryotic ribosomes: effect of inserting AUG triplets upstream from the coding sequence for preproinsulin

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

Contact Info

Product

Resources

About