Kruppel-like factor 2 transcriptional regulation involves heterogeneous nuclear ribonucleoproteins and acetyltransferases

Abstract

Kruppel-like factor 2 (KLF2) is expressed in several cell types, and knockout animals have shown that KLF2 gene regulation is involved in multiple biological processes. These include maintaining T-cells in the quiescent state, preventing preadipocytes from differentiating into mature adipocytes, stabilizing blood vessel walls through endothelial cell function, and advancing the later stages of lung development. Defining the regulation of KLF2 expression is important to understand these diverse functions. Promoter analysis of KLF2 has revealed that a region between -138 and -111 base pairs is required for its transcription, and this nucleotide sequence occurs in a region that is highly conserved in evolution. The present study was carried out to identify transcription factors that bind to this region of the KLF2 promoter. Nuclear factors were enriched by DNA affinity chromatography using the conserved nucleotide sequence of the KLF2 promoter. Mass spectrometry analysis of the proteins eluted from the affinity matrix identified several proteins, including glucose regulated protein-78 kDa (GRP-78), heterogeneous nuclear ribonucleoprotein (hnRNP)-U, hnRNP-D, CArG binding factor (CBF), P300/CBP associated factor (PCAF), cAMP response element binding protein (CREB) and SWI/SNF. The binding of these proteins to the highly conserved region of the KLF2 promoter element was tested by electrophoretic mobility supershift assays and chromatin immunoprecipitation analysis. These procedures confirmed that hnRNP-U, hnRNP-D, PCAF, and P-300 bind to the KLF2 promoter. Transactivation experiments demonstrated that these proteins are important for regulating KLF2 transcription. Of special interest is the role of hnRNPs in the transcription of the KLF2 gene.