title: Evidence that a consensus element found in naturally intronless mRNAs promotes mRNA export.
abstract: We previously showed that mRNAs synthesized from three genes that naturally lack introns contain a portion of their coding sequence, known as a cytoplasmic accumulation region (CAR), which is essential for stable accumulation of the intronless mRNAs in the cytoplasm. The CAR in each mRNA is unexpectedly large, ranging in size from ∼160 to 285 nt. Here, we identified one or more copies of a 10-nt consensus sequence in each CAR. To determine whether this element (designated CAR-E) functions in cytoplasmic accumulation of intronless mRNA, we multimerized the most conserved CAR-E and inserted it upstream of β-globin cDNA, which is normally retained/degraded in the nucleus. Significantly, the tandem CAR-E, but not its antisense counterpart, rescued cytoplasmic accumulation of β-globin cDNA transcripts. Moreover, dinucleotide mutations in the CAR-E abolished this rescue. We show that the CAR-E, but not the mutant CAR-E, associates with components of the TREX mRNA export machinery, the Prp19 complex and U2AF2. Moreover, knockdown of these factors results in nuclear retention of the intronless mRNAs. Together, these data suggest that the CAR-E promotes export of intronless mRNA by sequence-dependent recruitment of the mRNA export machinery.
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Haixin
authors.initials: H
authors.lastname: Lei
authors.forename: Bo
authors.initials: B
authors.lastname: Zhai
authors.forename: Shanye
authors.initials: S
authors.lastname: Yin
authors.forename: Steve
authors.initials: S
authors.lastname: Gygi
authors.forename: Robin
authors.initials: R
authors.lastname: Reed
mesh_terms: D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D016384:Consensus Sequence; D003593:Cytoplasm / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000037:antagonists & inhibitors; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D000072260:RNA Splicing Factors; D034443:RNA Transport; D012333:RNA, Messenger / Q000737:chemistry* / Q000378:metabolism*; D038621:Regulatory Sequences, Ribonucleic Acid; D012261:Ribonucleoproteins / Q000037:antagonists & inhibitors; D000072668:Splicing Factor U2AF
chemical_list: D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D000072260:RNA Splicing Factors; D012333:RNA, Messenger; D038621:Regulatory Sequences, Ribonucleic Acid; D012261:Ribonucleoproteins; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human; D045643:DNA Repair Enzymes; C417041:PRPF19 protein, human