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Differential localization and androgen sensitivity of prostatic nuclear protein kinases in euchromatin and heterochromatin fractions
Author(s) -
Norvitch Mary Ellen,
Ahmed Khalil
Publication year - 1986
Publication title -
the prostate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.295
H-Index - 123
eISSN - 1097-0045
pISSN - 0270-4137
DOI - 10.1002/pros.2990090203
Subject(s) - euchromatin , heterochromatin , chromatin , biology , non histone protein , nuclear protein , heterochromatin protein 1 , biochemistry , kinase , phosvitin , microbiology and biotechnology , protein kinase a , transcription factor , dna , gene
We have examined the distribution and androgenic regulation of protein kinases and phosphoproteins in euchromatin and heterochromatin fractions of rat ventral prostate chromatin. Available procedures to prepare euchromatin and heterochromatin fractions were found to result in the loss of various chromatin‐associated protein kinases even though there was no gross change in the gel electrophoretic profile of proteins in these fractions. This loss was prevented by the addition of 0.5 mM phenylmethylsulfonyl fluoride throughout the preparative procedures, which indicates that the protein kinases associated with the chromatin may be particularly susceptible to proteolytic degradation during further subfractionation. By utilizing an improved method for fractionation of chromatin, we have demonstrated a marked enrichment of protein kinase activity (towards phosvitin and endogenous chromosomal proteins) in the euchromatin fraction as compared with heterochromatin. Both of these fractions were also examined for the incorporation of 32 P into two main classes of nonhistone proteins (namely, H 2 SO 4 ‐soluble and ‐insoluble nonhistones). The amount of 32 P incorporated into heterochromatin‐associated proteins of both classes was markedly less than that in the euchromatin‐associated proteins. Protein kinase activities (especially those active towards phosvitin and nonhistone proteins) in the euchromatin fraction as compared with the heterochromatin were significantly reduced within 24 h after androgenic deprivation in the animal. The decreased phosphorylation of nonhistone proteins could be attributed to the loss of endogenous protein kinase activity. The results indicate that not only are chromatin‐associated protein phosphokinases preferentially localized in euchromatin fractions but also that these euchromatin‐associated protein kinases display the greatest sensitivity to androgenic status of the animal.