In:
European Journal of Biochemistry, Wiley, Vol. 130, No. 3 ( 1983-02), p. 447-456
Abstract:
We studied phosphoproteins and protein kinases in livers from normal rats and rats fed a diet containing 3′‐methyl‐ p ‐dimethylaminoazobenzene, an azo‐dye carcinogen. Endogenous phosphophortein patterns obtained by incubation of soluble and insoluble cell fractions with [γ‐ 32 P]ATP were different for livers from rats submitted to carcinogenic diet as soon as the 12th week of the regimen compared to the patterns of normal and regenerating liver. New Phosphorylated bands appeared during hepatocarcinogenesis in soluble as well as in particulate fractions. None of these bands was phosphorylatedon tyrosine residues and the global percentage of phosphotyrosine residues among phosphoproteins did not increase during the course of azo‐dye hepatocarcinogenesis. Electrophoresis of active enzymes showed, from the 12th week of carcinogenic diet, a new band identified as a cAMP‐dependent histone kinase. This form was absent in fetal liver and in regenerating liver following partial hepatectomy. It could be identified as a modified (or a new isozymic) form of protein kinase type II by its chromatographic properties and the nature of its photoaffinity‐labeled regulatory subunits. The ratio of the R 1 to R 2 regulatory subunits increased in the treated animals, but this phenomenon seemed to be due to cell proliferation rather than to malignancy as it was also observed in regenerating liver following partial hepatectomy. In hepatoma, the increase of the amount of R 1 subunits was not associated with a concomitant increase of protein kinase type I activity, which seemed to indicate that, in these tissues, a pool of free R 1 subunits could exist. Finally, combination of DEAE‐cellulose chromatography fractionation and cellulose acetate electrophoresis analysis allowed us to detect in hepatoma a phosvitin kinase band insensitive to cyclic nucleotides and heparin, inactive on casein, which was absent in normal liver. Hepatoma extracts also contained fast‐migrating caseinphosvitin kinase forms which could correspond to modified casein kinase II.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1983.130.issue-3
DOI:
10.1111/j.1432-1033.1983.tb07171.x
Language:
English
Publisher:
Wiley
Publication Date:
1983
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
2172518-4
SSG:
12
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