A novel nuclear protein in rat ventral prostate. Androgen-dependent and age-related change

A novel protein was found in the nuclei of rat ventral prostate. This protein has a molecular weight of about 21 kDa as measured by SDS-polyacrylamide gel electrophoresis. It showed a characteristic change between 3 and 84 weeks after birth in close association with the level of testosterone in the blood. After castration, the level of the 21-kDa protein decreased to 1/60 of normal in 7 days, but on daily injection of testosterone the level was restored to normal in 8 days and to twice the normal level in 14 days. Unlike H1 and H1(0) histone and high mobility group proteins, the 21-kDa protein was not extracted with 5% HClO4, but was partially extracted with 0.35 M NaCl. The 21-kDa protein was not found in kidney, liver, or bain, suggesting that it is specific to the ventral prostate.