Jason Seewoodhary


Steroid hormones are derived from a cholesterol precursor. They are secreted directly into the blood where they are bound to carrier proteins, which transport them to target cells. Due to their lipophilic nature they traverse cell membranes by simple diffusion and bind to Steroid Hormone Receptors (SHR’s).

The mechanism of action of SHR’s can be either genomic or non-genomic; this summary will hone in on how activation of SHR’s regulates gene expression. 

SHR’s are ligand-activated proteins that function as transcription factors, which direct and facilitate the transcription of DNA by RNA Polymerase II. They are located predominantly within the cytosol or nucleus of target cells. SHR’s have a central DNA binding domain (DBD), which via zinc finger and ‘P’ box motifs, targets the receptor to Hormone Response Elements (HRE’s).HRE’s are short sequences of DNA within the promoter region that conveys direct transcriptional responsiveness to genes. SHR’s also have a ligand binding domain (LBD), which acts as a molecular switch to turn on transcriptional activity when a hormonal ligand induces a conformational change in the receptor. Transactivation domains 1 and 2 (AF-1 and AF-2) are located close to the DBD and LBD respectively and upon hormone binding act synergistically to activate the SHR. The structure of a SHR is illustrated in figure 1 below (Beato M et al., 2000).


Steroids; Steroid Hormone Receptor; Co-Activator; Co-Repressor; Transcription Factor

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