In the canonical pathway, steroid hormone binding to a nuclear receptor (NR), often in the cytoplasm, causes the receptor to undergo a conformational change and translocate to the nucleus, where it interacts with specific sequences of DNA to regulate transcription.
In our analysis of FXR binding to hepatic chromatin, we showed that LRH-1 could function as a partner transcription factor for FXR on a small set of target genes through binding to a nuclear receptor half-site that was co-enriched with the FXR IR-1 element on a genome-wide scale [ 14].
These results are consistent with the idea that nuclear accumulation of Dcr1 is mediated by binding to a putative nuclear retention factor, which is likely to be mediated by this conserved surface.
The potent fat soluble seco-steroid hormone 1,25(OH)2D3 acts via binding to a corresponding nuclear receptor called the "vitamin D receptor" (VDR) [ 9– 11].
As such, 1,25(OH)2D exerts its effects by binding to a specific nuclear receptor (vitamin D receptor [VDR]), a ligand-dependent transcription factor that recognizes specific DNA sequences known as vitamin D response elements (DeLuca, 2004).
The translocated HSP90-bound AhR subsequently dissociates from the HSP90 complex by binding to a structurally related nuclear protein, aryl hydrocarbon receptor nuclear translocator (ARNT) [ 22].
Several promoter elements, such as CRE as well as those specific for binding to a variety of nuclear regulatory factors including Nf κB, NF-IL6, and myb, may play an important regulatory role in the transcription of the Cox-2 gene in a tissue-specific manner (Potter et al, 2000; Mestre et al, 2001; Tang et al, 2001).
Interestingly, the existence of an antioxidant-responsive element (ARE) activated through binding to Nrf2, a nuclear factor induced by the UPR program [38], was reported for the H- and L- isoforms of ferritin gene [39].
When considering that the nuclear proteins binding to a gene-control region prevent the methylation spreading of parasitic retroelements [ 34], the transitional-CpG sites reflect a balance between the methylation spreading and transcriptional activity.
Importin, a karyopherin, is involved in the transportation of protein molecules into the nucleus by binding to a specific recognition sequence, called the nuclear localization signal (NLS) [ 46].
However an ELISA-based Nrf2 binding assay demonstrated significantly higher levels of binding to an immobilised consensus ARE in nuclear extracts prepared from tg compared to wt hearts (Fig. 2H).
