Estrogenic Control of Spermidine/Spermine N1-Acetyltransferase Activity in Rat Uterus
It is widely accepted that specific intracellular receptor proteins are implicated in the estrogen regulation of gene expression, growth and differentiation in target cells. The unoccupied forms of these receptors, as suggested by Jensen and Jacobson1 and Gorski et al.,2 reside primarily in the cytoplasm and translocate to the nucleus after hormone interaction. A revision of this classical “two-step” model has recently indicated that both native and ligand-bound forms of the receptors are localized in the nucleus, as supported by biochemical3 and immunocytochemical4 data. The binding of estrogen with receptor leads to a change in the conformational state of the protein, which increases its affinity for nuclear components and DNA.3, 4 A number of nuclear acceptor sites have been proposed, including specific DNA sequences,5 ribonucleoprotein,6 basic nonhistone proteins, nuclear matrix,8 and acidic nonhistone protein DNA complexes.9 The binding of activated receptor with DNA or other nuclear components triggers the synthesis of specific proteins, growth, and differentiation in responsive tissues.
KeywordsFolic Acid Progesterone Androgen Estradiol Prolactin
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