Extinction of insulin gene expression in hybrids between beta cells and fibroblasts is accompanied by loss of the putative beta-cell-specific transcription factor IEF1.
AUTOR(ES)
Leshkowitz, D
RESUMO
Insulin-producing cells and fibroblasts were fused to produce hybrid lines. In hybrids derived from both hamster and rat insulinoma cells, no insulin mRNA could be detected in any of seven lines examined by Northern (RNA) analysis despite the presence in each line of the insulin genes of both parental cells. Hybrid cells were transfected with recombinant chloramphenicol acetyltransferase plasmids containing defined segments of the rat insulin I gene 5' flank. We observed no transcriptional activity of the intact insulin enhancer or of IEB2, a critical cis-acting element of the insulin enhancer. IEB2 has previously been shown to interact in vitro with IEF1, a DNA-binding activity observed selectively in insulin-producing cells. Hybrid cells showed no detectable IEF1 activity. Furthermore, the insulin enhancer was unable to reduce transcription directed by the Moloney sarcoma virus enhancer in a double-enhancer construct. Thus, extinction of insulin gene expression in the hybrids apparently does not operate through a direct action of repressors on the insulin enhancer; rather, extinction is accompanied by, and may be caused by, reduced DNA-binding activity of the putative transcriptional activator IEF1.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=369442Documentos Relacionados
- Hepatocyte nuclear factor 3beta is involved in pancreatic beta-cell-specific transcription of the pdx-1 gene.
- Individual protein-binding domains of the insulin gene enhancer positively activate beta-cell-specific transcription.
- A beta-cell-specific protein binds to the two major regulatory sequences of the insulin gene enhancer.
- Extinction of Ig genes expression in myeloma x fibroblast somatic cell hybrids is accompanied by repression of the oct-2 gene encoding a B-cell specific transcription factor.
- Extinction of T cell receptor alpha-chain gene expression accompanied by loss of the lymphoid enhancer-binding factor 1 (LEF-1) in murine somatic cell hybrids.
