title: An open reading frame element mediates posttranscriptional regulation of tropoelastin and responsiveness to transforming growth factor beta1.
abstract: Elastin, an extracellular component of arteries, lung, and skin, is produced during fetal and neonatal growth. We reported previously that the cessation of elastin production is controlled by a posttranscriptional mechanism. Although tropoelastin pre-mRNA is transcribed at the same rate in neonates and adults, marked instability of the fully processed transcript bars protein production in mature tissue. Using RNase protection, we identified a 10-nucleotide sequence in tropoelastin mRNA near the 5' end of the sequences coded by exon 30 that interacts specifically with a developmentally regulated cytosolic 50-kDa protein. Binding activity increased as tropoelastin expression dropped, being low in neonatal fibroblasts and high in adult cells, and treatment with transforming growth factor beta1 (TGF-beta1), which stimulates tropoelastin expression by stabilizing its mRNA, reduced mRNA-binding activity. No other region of tropoelastin mRNA interacted with cellular proteins, and no binding activity was detected in nuclear extracts. The ability of the exon-30 element to control mRNA decay and responsiveness to TGF-beta1 was assessed by three distinct functional assays: (i) insertion of exon 30 into a heterologous gene conferred increased reporter activity after exposure to TGF-beta1; (ii) addition of excess exon 30 RNA slowed tropoelastin mRNA decay in an in vitro polysome degradation assay; and (iii) a mutant tropoelastin cDNA lacking exon 30, compared to wild-type cDNA, produced a stable transcript whose levels were not affected by TGF-beta1. These findings demonstrate that posttranscriptional regulation of elastin production in mature tissue is conferred by a specific element within the open reading frame of tropoelastin mRNA.
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: R A
authors.initials: RA
authors.lastname: Pierce
authors.forename: H
authors.initials: H
authors.lastname: Wachi
authors.forename: R P
authors.initials: RP
authors.lastname: Mecham
authors.forename: W C
authors.initials: WC
authors.lastname: Parks
mesh_terms: D000818:Animals; D001483:Base Sequence; D003600:Cytosol / Q000378:metabolism; D005091:Exons; D005786:Gene Expression Regulation; D008168:Lung / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011485:Protein Binding / Q000187:drug effects; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014333:Tropoelastin / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D016212:Transforming Growth Factor beta; D014333:Tropoelastin