title: AUG sequences are required to sustain nonsense-codon-mediated suppression of splicing.
abstract: More than 90% of human genes are rich in intronic latent 5' splice sites whose utilization in pre-mRNA splicing would introduce in-frame stop codons into the resultant mRNAs. We have therefore hypothesized that suppression of splicing (SOS) at latent 5' splice sites regulates alternative 5' splice site selection in a way that prevents the production of toxic nonsense mRNAs and verified this idea by showing that the removal of such in-frame stop codons is sufficient to activate latent splicing. Splicing control by SOS requires recognition of the mRNA reading frame, presumably recognizing the start codon sequence. Here we show that AUG sequences are indeed essential for SOS. Although protein translation does not seem to be required for SOS, the first AUG is shown here to be necessary but not sufficient. We further show that latent splicing can be elicited upon treatment with pactamycin-a drug known to block translation by its ability to recognize an RNA fold-but not by treatment with other drugs that inhibit translation through other mechanisms. The effect of pactamycin on SOS is dependent neither on steady-state translation nor on the pioneer round of translation. This effect is found for both transfected and endogenous genes, indicating that SOS is a natural mechanism.
authors.affiliation: Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Kamhi
authors.forename: Galit
authors.initials: G
authors.lastname: Yahalom
authors.forename: Gideon
authors.initials: G
authors.lastname: Kass
authors.forename: Yael
authors.initials: Y
authors.lastname: Hacham
authors.forename: Ruth
authors.initials: R
authors.lastname: Sperling
authors.forename: Joseph
authors.initials: J
authors.lastname: Sperling
mesh_terms: D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000235:genetics; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000235:genetics; D002460:Cell Line; D018387:Codon, Initiator; D018389:Codon, Nonsense; D006224:Cricetinae; D017931:DNA Primers; D004080:Dihydroorotase / Q000235:genetics; D006801:Humans; D009154:Mutation; D010142:Pactamycin / Q000494:pharmacology; D010442:Peptide Chain Initiation, Translational; D016133:Polymerase Chain Reaction; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012322:RNA Precursors / Q000378:metabolism; D022821:RNA Splice Sites; D012326:RNA Splicing / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: C033626:CAD trifunctional enzyme; D018387:Codon, Initiator; D018389:Codon, Nonsense; D017931:DNA Primers; D011500:Protein Synthesis Inhibitors; D012322:RNA Precursors; D022821:RNA Splice Sites; D012333:RNA, Messenger; D010142:Pactamycin; D001221:Aspartate Carbamoyltransferase; D004080:Dihydroorotase; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)