A single nucleotide in an estrogen-related receptor α site can dictate mode of binding and peroxisome proliferator-activated receptor γ coactivator 1α activation of target promoters

The orphan nuclear receptor estrogen-related receptor alpha (ERR alpha, NR3B1) is a constitutively active transcription factor that controls multiple processes, most notably mitochondrial function. ERR alpha preferentially binds to a nine-nucleotide extended half-site sequence TNAAGGTCA, referred to as the ERRE, as either a monomer or a dimer, although how the mode of DNA binding is dictated remains to be determined. Here, we used variants of the extended half-site sequence and selective DNA binding domain mutants of ERR alpha to investigate the effects of ERRE sequence specificity on ERR alpha DNA binding mode, transactivation and interaction with the coactivator protein peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha). We found that the base at the N position of the TNAAGGTCA sequence dictated ERR alpha binding preference as a monomer or dimer. In addition, we demonstrated that the threonine residue at position 124 (Thr(124)) was a determinant of ERR alpha DNAdependent dimerization. Transfection experiments also indicated that substituting a thymidine for a cytosine at the N position in the ERRE of the native ERR alpha target promoter trefoil factor 1 (TFF1) considerably diminished the transcriptional response of the ERR alpha/PGC-1 alpha complex. These results suggest that a single nucleotide in an ERR alpha binding site can determine specific configuration to the receptor and productive interaction with the coactivator PGC-1 alpha.