Transcriptional and translational regulation of the Leri-Weill and Turner syndrome homeobox gene SHOX.
Regulation of gene expression is particularly important for gene dosage-dependent diseases and the phenomenon of clinical heterogeneity frequently associated with these phenotypes. We here report on the combined transcriptional and translational regulatory mechanisms controlling the expression of the Léri-Weill and Turner syndrome gene SHOX. We define an alternative promotor within exon 2 of the SHOX gene by transient transfections of mono- and bicistronic reporter constructs and demonstrate substantial differences in the translation efficiency of the mRNAs transcribed from these alternative promotors by in vitro translation assays and direct mRNA transfections into different cell lines. Although transcripts generated from the intragenic promotor (P2) are translated with high efficiencies, mRNA originating from the upstream promotor (P1) exhibit significant translation inhibitory effects due to seven AUG codons upstream of the main open reading frame (uAUGs). Site-directed mutagenesis of these uAUGs confers full translation efficiency to reporter mRNAs in different cell lines and after injection of Xenopus embryos. In conclusion, our data support a model where functional SHOX protein levels are regulated by a combination of transcriptional and translational control mechanisms.
Blaschke
Rudiger J
RJ
Institute of Human Genetics, Ruprecht-Karls-University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
Töpfer
Christine
C
Marchini
Antonio
A
Steinbeisser
Herbert
H
Janssen
Johannes W G
JW
Rappold
Gudrun A
GA
D020121:5' Untranslated Regions; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D003062:Codon; D015536:Down-Regulation; D005091:Exons; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D000074122:Short Stature Homeobox Protein; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection; D014424:Turner Syndrome / Q000378:metabolism*; D014981:Xenopus
D020121:5' Untranslated Regions; D003062:Codon; D018398:Homeodomain Proteins; D012333:RNA, Messenger; C106071:SHOX protein, human; D000074122:Short Stature Homeobox Protein; D014157:Transcription Factors; D012313:RNA; D008156:Luciferases