β-Cell differentiation factor Nkx6.1 contains distinct DNA binding inteference and transcriptional repression domains

Raghavendra G. Mirmira, Hirotaka Watadaf, Michael S. German

Research output: Contribution to journalArticle

52 Scopus citations

Abstract

β-Cell differentiation factor Nkx6.1 is a homeodomain protein expressed in developing and mature β-cells in the pancreatic islets of Langerhans. To understand how it contributes to β-cell development and function, we characterized its DNA binding and transactivation properties. A single copy of the homeodomain of Nkx6.1 binds to a strictly conserved 8-base pair DNA consensus sequence, TTAATTAC; even minor variations to this consensus reduce DNA binding affinity significantly. Full-length Nkx6.1, however, has markedly reduced DNA binding affinity due to an acidic domain at the carboxyl end of the molecule that functions as a mobile binding interference domain capable of interrupting the interaction between DNA and DNA binding domains of the helix-turn-helix type. When expressed in fibroblast cell lines, Nkx6.1 represses transcription through isolated Nkx6.1 binding sites; in β-cell lines, Nkx6.1 specifically represses the intact insulin promoter through TAAT-containing sequences. In Gal4 one-hybrid fusion studies, transcriptional repression maps to a discreet region within the amino terminus. Our findings suggest a model in which Nkx6.1, regulated by interactions through its carboxyl terminus, directs the repression of specific genes in developing and mature β-cells.

Original languageEnglish (US)
Pages (from-to)14743-14751
Number of pages9
JournalJournal of Biological Chemistry
Volume275
Issue number19
DOIs
StatePublished - May 12 2000
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of 'β-Cell differentiation factor Nkx6.1 contains distinct DNA binding inteference and transcriptional repression domains'. Together they form a unique fingerprint.

  • Cite this