Final answer:
Estrogen, progesterone, and glucocorticoids act on nuclear receptors, which are specialized proteins that regulate gene transcription by binding to specific DNA sequences.
Step-by-step explanation:
Estrogen, progesterone, and glucocorticoid act on nuclear receptors. These hormones are part of the steroid hormone group, which once in the target cell, bind to specific steroid hormone receptor proteins to form a hormone-receptor complex. This complex then binds to DNA regulatory elements of a gene to modulate transcription. Specifically, glucocorticoid receptors are zinc-finger transcription factors that bind to glucocorticoid response elements in the promoter sequences of target genes to regulate gene expression.