Role for the Rana catesbeiana homologue of C/EBP alpha in the reprogramming of gene expression in the liver of metamorphosing tadpoles.
During the spontaneous or thyroid hormone (TH)-induced metamorphosis of Rana catesbeiana, developmental changes occur in its liver that are necessary for the transition of this organism from an ammonotelic larva to a ureotelic adult. These changes include the coordinated expression of genes encoding the urea cycle enzymes carbamyl phosphate synthetase (CPS-I) and arnithine transcarbamylase (OTC). Although the expression of these genes is dependent on TH, the mechanisms(s) by which TH initiates this tissue-specific response is thought to be indirect and to involve early TH-induced upregulation of a gene(s), which, in turn, upregulates the coordinated expression of these urea-cycle enzyme genes. Herein, we demonstrate that mRNAs encoding the Rana homologue of the mammalian transcription factor C/EBP alpha (designated RcC/EBP-1) accumulate early in response to TH and that the product of these mRNAs can bind to and transactivate the promoters of both the Rana CPS-1 and OTC genes. These results support the contention that the reprogramming of gene expression in the liver of metamorphosing tadpoles involves a TH-induced cascade of gene activity in which RcC/EBP-1 and, perhaps, other transcription factors coordinate the expression of genes, such as those encoding CPS-I and OTC, whose products are characteristic of the adult liver phenotype.
Chen
Y
Y
Department of Zoology, University of Western Ontario, London, Canada.
Atkinson
B G
BG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D005796:Genes; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology*; D009954:Ornithine Carbamoyltransferase / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D011892:Rana catesbeiana / Q000235:genetics* / Q000254:growth & development; D011988:Receptors, Thyroid Hormone / Q000235:genetics; D015533:Transcriptional Activation; D014284:Triiodothyronine / Q000494:pharmacology; D015854:Up-Regulation
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D009954:Ornithine Carbamoyltransferase; D002222:Carbamoyl-Phosphate Synthase (Ammonia)