An AU-rich stem-loop structure is a critical feature of the perinuclear localization signal of c-myc mRNA.
In eukaryotic cells, several mRNAs including those of c-myc and c-fos are localized to the perinuclear cytoplasm and associated with the cytoskeleton. The localization element of c-myc mRNA is present within its 3'UTR (3'-untranslated region) but the precise nature of this signal has remained unidentified. Chemical/enzymatic cleavage with RNases (ribonucleases) and lead have identified single-stranded and double-stranded regions in RNA transcripts of nucleotides 194-280 of the c-myc 3'UTR. Combined with computer predicted structure these results indicate that this region folds so that part of it forms a stem-loop structure. A mutation, that has been previously shown to prevent localization, leads to a different secondary RNA structure in this region as indicated by altered cleavage patterns. Competitive gel-retardation assays, using labelled transcripts corresponding to nucleotides 205-280 of c-myc 3'UTR, and fibroblast extracts revealed that the stem-loop region was sufficient for RNA-protein complex formation. In situ hybridization studies in cells transfected with reporter constructs, in which all or parts of the region corresponding to this stem-loop were linked to beta-globin, indicated that this region was sufficient for localization and that deletion of the nucleotides corresponding to the proposed upper-stem or terminal loop prevented localization. Our hypothesis is that an AU-rich stem-loop structure within nt 222-267 in the c-myc 3'UTR forms the perinuclear localization signal. Bioinformatic analysis suggests that this signal shares features with 3'UTRs of other localized mRNAs and that these features may represent a conserved form of signal in mRNA localization mechanisms.
Chabanon
Hervé
H
Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle-upon-Tyne NE2 4HH, UK.
Mickleburgh
Ian
I
Burtle
Brian
B
Pedder
Christopher
C
Hesketh
John
J
D020413:3' Untranslated Regions / Q000235:genetics; D020856:AT Rich Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D017353:Gene Deletion; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D051379:Mice; D009690:Nucleic Acid Conformation; D034443:RNA Transport; D012333:RNA, Messenger / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid
D020413:3' Untranslated Regions; D012333:RNA, Messenger