STRUCTURAL-CHANGES IN HEPATIC NUCLEAR CHROMATIN AFTER INDUCTION OF VITELLOGENESIS WITH 17-BETA ESTRADIOL IN ATLANTIC SALMON (SALMO-SALAR)

1. This paper reviews studies on changes in hepatic nuclei during the 17-beta estradiol-induced synthesis of vitellogenin in the liver of At lantic salmon (Salmo salar). 2. The effects of the hormone on chromati n structures and the expression of the vitellogenin gene are described . 3. The participation of a 21 kDa protein in the hormone-mediated cha nges in the gene expression, and alterations in chromatin structures, are discussed. The protein is similar, but not identical, to the rainb ow trout (Oncorhynchus mykiss) high-mobility group protein D. This und erlines species-dependent differences between proteins within the Salm onidae family. 4. To diminish the expression of the genes not required for vitellogenesis, large chromatin domains become condensed under th e influence of 17-beta estradiol. Polyamines increase in concentration and participate in the stabilization of the chromatin structures.