Interaction of the CNC-bZIP factor TCF11/LCR-F1/Nrf1 with MafG: Binding-site selection and regulation of transcription

Abstract

We have previously shown that the widely expressed human transcription factor TCF11/LCR-F1/Nrf1 interacts with small Maf proteins and binds to a subclass of AP1-sites. Such sites are required for beta-globin 5' DNase I hypersensitive site 2 enhancer activity, erythroid porphobilinogen deaminase inducibility, hemin responsiveness by heme-oxygenase 1 and expression of the gene NAD(P)H:quinone oxidoreductase1. Here we report the optimal DNA-binding sequences for TCF11/LCR-F1/Nrf1 alone and as a heterodimer with MafG, identified by using binding-site selection. The heterodimer recognises a 5'-TGCTgaGTCAT-3' binding-site that is identical to the established NF-E2-site, the antioxidant response element and the heme-responsive element while the binding specificity of the homomer is less stringent. To investigate the activity of TCF11 through this selected site, both alone and in the presence of MafG, we have used a transient transfection assay. TCF11 alone activates transcription while MafG alone acts as a repressor. When co-expressed, MafG interferes with TCF11 transactivation in a dose dependent manner. This indicates that MafG protein, which heterodimerises efficiently with TCF11 in vitro (the heterodimer having a higher affinity for DNA than TCF11 alone), does not co-operate with TCF11 in transactivating transcription. We propose that since both these factors are widely expressed, they may act together to contribute to the negative regulation of this specific target site. Efficient positive regulation by TCF11 may require alternative partners with perhaps more restricted expression patterns.

A global role for KLF1 in erythropoiesis revealed by ChIP-seq in primary erythroid cells

“…6). More interestingly we found enrichment of an AP-1-type motif (represented by TCF11-MafG bZIP [Johnsen et al 1998]) and Smad (represented by Smad3) motifs in both types of regions (Fig. 6).…”

“…6). The AP-1-like motif (TCF11-MafG bZIP [ Johnsen et al 1998]) is most likely bound by bZIP heterodimers like p45-NFE2/p18-MAF which are important in erythropoiesis (Andrews et al 1993;Kotkow and Orkin 1995;Johnsen et al 1998). Interestingly a member of the Smad family of transcription factors, Smad5, is partly responsible for the induction of Klf1 expression in erythroid cells (Lohmann and Bieker 2008).…”

Family based association analysis of the IL2 and IL15 genes in allergic disorders

“…Johnsen et al 35 proposed that the TCF11/MafG complex may contribute to the negative regulation of transactivating transcription. This corroborates that the T allele may induce a relative decrease in IL2 expression and offers a possible molecular explanation that should be experimentally tested.…”

Two Domains of the Human bZIP Transcription Factor TCF11 Are Necessary for Transactivation

“…COS-1, HeLa, or HepG2 cells were transfected at 50 -80% confluence either using a standard calcium phosphate procedure (16) or FuGENE 6, following the supplier's instructions (Roche Molecular Biochemicals). For calcium phosphate transfection, 5 g of TCF11 expression construct, 2 g of PBGD3.2Luc reporter (16), and 1 g of internal control (pRSVCAT)/10-cm dish were used.…”

“…More recent results show that these factors, originally thought to be widely expressed, are differentially expressed during development and might therefore regulate TCF11 in a tissue-specific manner (14,15). Both MafG and MafK repress transactivation when coexpressed with TCF11 compared with the level of reporter gene transcription induced by TCF11 alone in transient transfections (13,16). However, these factors are also partners of several other bZIP proteins (for an overview, see Ref.…”