Importance of substrate conformation in the phosphorylation of chromatin-associated proteins by exogenous protein kinase C.
Protein kinase C (PKC)-mediated phosphorylation of chromatin-associated proteins was studied in vitro. HL-60 and HeLa nuclear proteins were notably unresponsive to exogenously added brain PKC. In contrast, 3T3 fibroblasts and lymphocytes from primary cultures exhibited PKC-dependent phosphorylation of chromatin-associated proteins when chromatin was induced to expand. Unexpanded nuclei in all cell lines were unresponsive. Responsiveness was particularly obvious in the decondensed chromatin of primary lymphocytes, where a large number of proteins were phosphorylated in response to exogenous PKC. DNAase-I and micrococcal nuclease strongly modulated these phosphorylation patterns indicating that the substrates were DNA-associated. It was concluded that although substrate conformation, i.e. condensation state, was the primary determining factor in control of PKC-dependent nuclear protein phosphorylation, different cell lines greatly differ in their overall responsiveness to exogenous PKC.
Testori
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School of Biological Sciences, Flinders University of South Australia, Adelaide.
Burgoyne
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Murray
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D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D011487:Protein Conformation; D011493:Protein Kinase C / Q000494:pharmacology*; D051381:Rats; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
D002843:Chromatin; D011493:Protein Kinase C