title: Identification of alternative promoter usage for the matrix Gla protein gene. Evidence for differential expression during early development in Xenopus laevis.
abstract: Recent cloning of the Xenopus laevis (Xl) matrix Gla protein (MGP) gene indicated the presence of a conserved overall structure for this gene between mammals and amphibians but identified an additional 5'-exon, not detected in mammals, flanked by a functional, calcium-sensitive promoter, 3042 bp distant from the ATG initiation codon. DNA sequence analysis identified a second TATA-like DNA motif located at the 3' end of intron 1 and adjacent to the ATG-containing second exon. This putative proximal promoter was found to direct transcription of the luciferase reporter gene in the X. laevis A6 cell line, a result confirmed by subsequent deletion mutant analysis. RT-PCR analysis of XlMGP gene expression during early development identified a different temporal expression of the two transcripts, strongly suggesting differential promoter activation under the control of either maternally inherited or developmentally induced regulatory factors. Our results provide further evidence of the usefulness of nonmammalian model systems to elucidate the complex regulation of MGP gene transcription and raise the possibility that a similar mechanism of regulation may also exist in mammals.
authors.affiliation: University of Algarve CCMAR, Campus de Gambelas, Faro, Portugal.
authors.forename: Natércia
authors.initials: N
authors.lastname: Conceição
authors.forename: Ana C
authors.initials: AC
authors.lastname: Silva
authors.forename: João
authors.initials: J
authors.lastname: Fidalgo
authors.forename: José A
authors.initials: JA
authors.lastname: Belo
authors.forename: M Leonor
authors.initials: ML
authors.lastname: Cancela
mesh_terms: D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000235:genetics*; D016384:Consensus Sequence; D004625:Embryo, Nonmammalian / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D035181:TATA-Box Binding Protein / Q000378:metabolism; D014158:Transcription, Genetic; D029867:Xenopus Proteins / Q000235:genetics; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics* / Q000254:growth & development*; D000097568:Matrix Gla Protein
chemical_list: D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D035181:TATA-Box Binding Protein; D029867:Xenopus Proteins; D000097568:Matrix Gla Protein