Steroid hormones exert their genomic effects via nuclear receptors. Which domain of a nuclear receptor directly contacts the specific DNA sequence (hormone response element)?

• A Ligand-binding domain (LBD)
• B DNA-binding domain (DBD) with zinc-finger motifs ✓
• C N-terminal activation function-1 (AF-1) domain
• D Hinge region

Explanation

The DNA-binding domain (DBD) of nuclear receptors contains two zinc-finger motifs (Cys2-Cys2 type). The first zinc finger determines DNA-binding specificity to hormone response elements (HREs), while the second zinc finger participates in receptor dimerization. Binding to HREs in gene promoters facilitates transcriptional activation or repression. The ligand-binding domain binds the hormone and regulates receptor activation/dimerization. The AF-1 domain provides ligand-independent transactivation. The hinge region connects LBD and DBD and is involved in nuclear localization.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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