The steroid hormone receptors (SHRs) play an important role in many physiological and pathological processes including endocrine cancers. However, the precise mechanisms by which these SHRs pass signals from a hormone to control gene expression remain a central unresolved problem, which has limited SHRs therapeutic utilities in a cell/tissue specific manner. Role of the activation function-1 (AF1) in this process is of immense importance as it provides platforms for interactions of specific co-regulatory proteins, and thereby dictates the final outcome SHR-regulated target gene expression. The AF1 located in the N-terminal domain (NTD) plays a critical role in regulating cell/tissue-specific effects of SHRs. However, the exact mechanism of this action is not known. It has been suggested that cell/tissue-specific activities of SHRs may be due to AF1 conformations and subsequent coactivator interactions. The SHRs’ NTD/AF1 has been reported to exist in an intrinsically disorder conformation and undergoes disorder-order transition through intra- and inter- molecular allosteric regulations. In the study, we tested whether the flanking sequences around AF1 affect glucocorticoid receptor (GR) activity due, in part, to conformational changes in otherwise ID AF1 that can facilitate its interaction with critical coregulatory proteins such as TATA Box-Binding Protein (TBP) and steroid receptor coactivator-1 (SRC-1). Using biophysical techniques, we found that placing AF1 immediately upstream from the DNA binding domain (DBD) results into acquisition of a relatively ordered conformation in GR AF1. Further analyses revealed that removing amino acid sequences (1-76) prior to AF1 or removal of amino acids (263-420) between AF1 and DBD differentially regulates AF1-mediated GR activity. The results from this study may provide a potential mechanism for cell-dependent differing GR activities as well as other SHRs and thereby, our results may provide additional SHR selectivity needed to target cell-tissue specific gene regulations in current endocrine-based therapies.

Citation Format: Shagufta H. Khan, Raj Kumar. Role of amino acid sequences within the N terminal domain in regulating AF1-mediated glucocorticoid receptor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3085.