Extinction of alpha 1-antitrypsin gene expression in somatic cell hybrids: evidence for multiple controls.

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  • Additional Information
    • Source:
      Publisher: Cold Spring Harbor Laboratory Press Country of Publication: United States NLM ID: 8711660 Publication Model: Print Cited Medium: Print ISSN: 0890-9369 (Print) Linking ISSN: 08909369 NLM ISO Abbreviation: Genes Dev Subsets: MEDLINE
    • Publication Information:
      Publication: Cold Spring Harbor, NY : Cold Spring Harbor Laboratory Press
      Original Publication: [Cold Spring Harbor, N.Y.] : Cold Spring Harbor Laboratory in association with the Genetical Society of Great Britain, [c1987-
    • Subject Terms:
      DNA-Binding Proteins* ; Nuclear Proteins*; Gene Expression Regulation/*genetics ; Transcription Factors/*genetics ; alpha 1-Antitrypsin/*genetics; Animals ; Base Sequence ; Blotting, Northern ; Chloramphenicol O-Acetyltransferase/genetics ; Chloramphenicol O-Acetyltransferase/metabolism ; Hepatocyte Nuclear Factor 1 ; Hepatocyte Nuclear Factor 1-alpha ; Hepatocyte Nuclear Factor 1-beta ; Hybrid Cells ; Molecular Sequence Data ; Mutation/genetics ; Promoter Regions, Genetic/genetics ; Rats ; Recombinant Fusion Proteins/genetics ; Recombinant Fusion Proteins/metabolism ; Transcriptional Activation ; Transfection ; beta-Galactosidase/genetics ; beta-Galactosidase/metabolism
    • Abstract:
      Expression of the liver-specific alpha 1-antitrypsin (alpha 1AT) gene is extinguished in hepatoma/fibroblast hybrids. To define the mechanism of extinction, we identified DNA sequences involved in this process by transiently transfecting mutant alpha 1AT promoters into parental and hybrid cells. The wild-type alpha 1AT promoter (-554 to +44 bp) was highly expressed in rat hepatoma cells, but activity was 100-fold less in fibroblasts or cell hybrids. Mutations in this region failed to activate alpha 1AT expression in nonhepatic cells, but mutations in the binding site for liver factor B1 (LF-B1) reduced hepatic-specific expression greater than 100-fold. Furthermore, the hybrid cells failed to express LF-B1-binding activity and mRNA. This suggested that alpha 1AT extinction in hybrids might be an indirect, lack-of-activation phenotype mediated primarily through repression of LF-B1. To test this possibility, we stably transfected an LF-B1 expression cassette into parental and hybrid cells and monitored expression of transfected and endogenous alpha 1AT genes. Surprisingly, although constitutive LF-B1 expression could activate alpha 1AT-CAT transgenes in these cells, it neither prevented nor reversed extinction of the chromosomal alpha 1AT genes. We conclude that although extinction of the LF-B1 trans-activator accompanies alpha 1AT extinction in cell hybrids, it does not play a causal role in this process.
    • Grant Information:
      GM26449 United States GM NIGMS NIH HHS
    • Gene Symbol:
      aAT; LF-B1
    • Accession Number:
      0 (DNA-Binding Proteins)
      0 (Hepatocyte Nuclear Factor 1-alpha)
      0 (Hnf1a protein, rat)
      0 (Nuclear Proteins)
      0 (Recombinant Fusion Proteins)
      0 (Transcription Factors)
      0 (alpha 1-Antitrypsin)
      126548-29-6 (Hepatocyte Nuclear Factor 1)
      138674-15-4 (Hepatocyte Nuclear Factor 1-beta)
      EC 2.3.1.28 (Chloramphenicol O-Acetyltransferase)
      EC 3.2.1.23 (beta-Galactosidase)
    • Publication Date:
      Date Created: 19920201 Date Completed: 19920316 Latest Revision: 20190516
    • Publication Date:
      20240829
    • Accession Number:
      10.1101/gad.6.2.316
    • Accession Number:
      1737621