Negative autoregulation of HNF-4α gene expression by HNF-4α1

HNF-4α (hepatocyte nuclear factor-4α) is required for tissue-specific expression of many of the hepatic, pancreatic, enteric and renal traits. Heterozygous HNF-4α mutants are inflicted by MODY-1 (maturity onset diabetes of the young type-1). HNF-4α expression is reported here to be negatively autoregulated by HNF-4α1 and to be activated by dominant-negative HNF-4α1. Deletion and chromatin immunoprecipitation analysis indicated that negative autoregulation by HNF-4α1 was mediated by its association with the TATA-less HNF-4α core promoter enriched in Sp1, but lacking DR-1 response elements. Also, negative autoregulation by HNF-4α1 was independent of its transactivation function, being similarly exerted by transcriptional-defective MODY-1 missense mutants of HNF-4α1, or under conditions of suppressing or enhancing HNF-4α activity by small heterodimer partner or by inhibiting histone deacetylase respectively. Negative autoregulation by HNF-4α1 was abrogated by overexpressed Sp1. Transcriptional suppression by HNF-4α1 independently of its transactivation function may extend the scope of its transcriptional activity to interference with docking of the pre-transcriptional initiation complex to TATA-less promoters.