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

Raghu Mirmira, Hirotaka Watadaf, Michael S. German

Research output: Contribution to journalArticle

52 Citations (Scopus)

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

Fingerprint

Cell Differentiation
DNA
Islets of Langerhans
Cells
Homeodomain Proteins
Cell Line
DNA sequences
Consensus Sequence
Transcription
Fibroblasts
Base Pairing
Transcriptional Activation
Fusion reactions
Genes
Binding Sites
Insulin
Molecules

ASJC Scopus subject areas

  • Biochemistry

Cite this

β-Cell differentiation factor Nkx6.1 contains distinct DNA binding inteference and transcriptional repression domains. / Mirmira, Raghu; Watadaf, Hirotaka; German, Michael S.

In: Journal of Biological Chemistry, Vol. 275, No. 19, 12.05.2000, p. 14743-14751.

Research output: Contribution to journalArticle

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