Influence of flanking sequences on signaling between the activation function AF1 and DNA-binding domain of the glucocorticoid receptor.

Despite their importance in gene regulation, the exact mechanisms of glucocorticoid receptor's (GR's) N-terminal activation function region, AF1, which exists in an intrinsically disordered (ID) conformation remains largely unknown. For its interaction with critical coregulatory proteins, AF1 must be malleable and capable of presenting varied interaction surfaces. We hypothesize that various confluences of effects, including intra-molecular signaling between the AF1 and the GR DNA-binding domain (DBD) cause functional structure to form in AF1. In this study, we tested the effect of the amino acid sequences surrounding AF1 on the propensity of AF1 to gain structure when connected to DBD. Removal of amino acids between AF1 and DBD results in the formation of more ordered conformation in AF1. In addition, sequences flanking the AF1 may play an inhibitory role in AF1 activity. These results suggest a mechanism as to why certain GR isoforms with truncated N-terminal domains show altered transcriptional activity.