Analysis of factors in regulating transcription of the human insulin receptor gene.

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04671492
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 内分泌・代謝学
• Research Institution: Kumamoto University
• Principal Investigator: KISHIKAWA Hideki Kumamoto University School of Medicine, University Hospital, Research Assistant, 医学部・附属病院, 助手 (30161441)
• Co-Investigator(Kenkyū-buntansha): SAKAKIDA Michiharu Kumamoto University School of Medicine, University Hospital, Research Assistant, 医学部・附属病院, 助手 (50170577) ; SHICHIRI Motoaki Kumamoto University School of Medicine, Professor, 医学部, 教授 (00028515)
• Project Period (FY): 1992 – 1993
• Keywords: insulin receptor / nuclear protein / HepG2 cells

Research Abstract

After the isolation of the promotor region of the human insulin receptor gene, we identified the major transcription factor and compared the insulin receptor promotor activity among different cells.
1. CHO cells, transfected with insulin receptor promotor-Chloram-phenicol acetyl transferase (CAT) fusion plasmid, were incubated with dexamethasone, glucagon or Phorbol ester (TPA) and the changes of CAT activity were compared. There were no regions responding to above materials in 1.5 Kb upstream from insulin receptor gene translation initiation site.
2. Deletion analyzes of promotor region of insulin receptor gene were perfomed using HepG2 (human hepatoma derived cell line), COS or CHO (Chinese hamster ovary) cells. In COS and CHO cells, four GC boxes about 600 base pairs upstream from translation initiation site which were potential Spl binding sites were found to be important for transcriptional activation. Gel shift assay and DNAase foot printing using partially purified LacZ-Spl hybrid proteins showed that Spl bound to these four GC boxes. HepG2 cells appeared to have addiferent tarnscription regulation in insulin receptor gene promotor from other cells. In conclusion, the transcription of insulin receptor gene is mainly regulated by Spl and the factors regulating IR promotor might be different among cells. The presense of unknown protein influencing insulin receptor promotor activity is suggested. We are now continueing further characterization of this factor.