Nuclear matrix fraction was isolated from rat ventral prostatic nuclei previously incubated with [γ-32P]ATP to label nuclear phosphoproteins with 32P. A significant portion of the radioactivity was recovered in the phosphoproteins intrinsic to the nuclear matrix fraction. At 12 h after androgen deprivation (i.e., when a significant portion of the nuclear androgen receptor was known to be depleted), the rate, but not the extent, of phosphorylation of nuclear proteins (predominantly nonhistone proteins) was markedly reduced. Nuclear matrix fraction isolated from such preparations demonstrated a profound reduction in the rate of incorporation of 32P into the matrix-associated proteins without any apparent change in the gel electrophoretic profile of these proteins. The results indicate that the cAMP-independent protein kinase activity which catalyzes the phosphorylation of nuclear matrix proteins is under androgenic control. This may be germane to nuclear matrix-associated initial events in androgen action.
Bibliographical noteFunding Information:
This work was supported in part by Research Grant CA-15662 from National Cancer Institute, DHHS, PHS, and funds from the V. A. Medical Research Fund. We thank Miss Kathleen Ferkul for valuable assistance in this work. Ms. Margaret Chelmo assisted in preparation of the manuscript.