Determination of mRNA fate by different RNA polymerase II promoters.
Translational stop mutations of the human beta-globin gene cause a reduction of cytoplasmic mRNA accumulation in thalassemia patients and in transfection models. The exact mechanism underlying this phenomenon has remained enigmatic but is known to be post-transcriptional. We have used transfected HeLa cells to study the expression of beta-globin mRNAs with nonsense or frameshift mutations within the three exons of this gene. Mutations in exons 1 or 2 reduce cytoplasmic mRNA accumulation whereas a mutation in exon 3 permits essentially normal expression. We report here that the post-transcriptional fate of mutated beta-globin mRNAs is differentially affected by the type of RNA polymerase II promoter driving expression. Replacement of the beta-globin promoter with the herpes simplex virus type 1 thymidine kinase gene promoter but not the cytomegalovirus immediate early promoter rescues the cytoplasmic accumulation of mutated mRNA to wild-type levels. This effect is shown to be independent of the absolute quantity and the kinetics of accumulation of mutated mRNA synthesized, and primer-extension analyses confirm that both viral promoters accurately utilize identical transcription start sites. These data thus reveal an unexpected property of RNA polymerase II promoters: determination of the post-transcriptional fate of the maturing mRNA, presumably by influencing alternative choices between as yet undefined processing and/or transport pathways.
Enssle
J
J
Department of Pediatrics II, University of Ulm, Germany.
Kugler
W
W
Hentze
M W
MW
Kulozik
A E
AE
D001483:Base Sequence; D003587:Cytomegalovirus / Q000235:genetics; D017931:DNA Primers; D005091:Exons; D016368:Frameshift Mutation; D015870:Gene Expression; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics; D006367:HeLa Cells; D018259:Herpesvirus 1, Human / Q000235:genetics; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D013937:Thymidine Kinase / Q000235:genetics; D014158:Transcription, Genetic
D017931:DNA Primers; D017874:Immediate-Early Proteins; D012333:RNA, Messenger; D005914:Globins; D013937:Thymidine Kinase; D012319:RNA Polymerase II