Nuclear proteins in the heart of the cardiomyopathic Syrian hamster. Phosphorylation of phenol-soluble nonhistone proteins.

Abstract

We examined incorporation of 32 P into phenol-soluble nonhistone nuclear acidic proteins (NHNP) obtained from myolytic, hypertrophic, and failing phases of hamster cardiomyopathy. NHNP from these dystrophic hamster hearts were phosphorylated much less than their controls, despite a 9-fold increase in uptake of 32 P into their nuclei. After fractionation of NHNP by isoelectrofocusing polyacrylamide gel electrophoresis, two major fractions focusing from pH 6.0 to 6.2 and 6.6 to 6.8 were highly phosphorylated in both the control and dystrophic hearts. The latter fraction was much more phosphorylated in the control. Two fractions of NHNP focusing at pH 4.9 and 5.1 were more highly phosphorylated in the dystrophic hearts than in the controls. Autoradiographs obtained from the two-dimensional polyacrylamide slab gel electrophoresis showed that two proteins (pH 4.9 and 5.1; mol wt 25,000 and 60,000, respectively) were highly phosphorylated in the dystrophic heart. There was no detectable phosphoryl-ation of these proteins in the controls. These changes in the phosphorylation of cardiac NHNP may be important in determining the alteration of gene expression in hamster cardiomyopathy. HISTONE and nonhistone chromatin proteins or nonhis-tone nuclear proteins (NHNP) are known to be associated with DNA in eukaryotic cells. 1 Histones can be fraction-ated into five major components which show a striking similarity in all species and in all tissues of an organism. 2 NHNP are highly heterogeneous, exhibiting some degree of quantitative and qualitative variations in different tissues. This class of proteins has been implicated in the control of differential gene expression in higher organisms. :> ~ l() There is evidence that changes in genetic activity are accompanied by alterations in NHNP. Several specific NHNP have been reported to be altered under different physiological states such as cell differentiation and hormone treatment."" 15 There also is considerable evidence that phosphorylation of NHNP is coupled to gene activation. Recent studies by Kleinsmith and co-workers, and others 1B ~ 20 indicate that the phosphorylation and dephos-phorylation of NHNP may be important in the regulation of gene transcription. Specific phosphorylation and de-phosphorylation of NHNP have been shown to occur in differential gene activation by aldosterone 21 and cyclic AMP. 22 The cardiomyopathic hamster is a genetic model of myocardial disease. 23 As the cardiomyopathy develops naturally, without surgical intervention, this paradigm has proved useful in the study of the biochemical events associated with cardiac hypertrophy and failure. Nair and co-workers 24 have shown an increase in DNA-dependent From the RNA polymerase activity in nuclear preparations derived from the hearts of cardiomyopathic hamsters in the "my-olytic" or "necrotic" phase of the disease. There is no report examining the metabolism of nuclear proteins in cardiomyopathic hamsters. In an earlier study, we demonstrated alterations in NHNP composition of myocardium from patie...

A ribosomal defect in dystrophic hamsters

“…26 and 27) and it has recently been suggested that variations in the degree of phosphorylation of ribosomal proteins may induce conformational changes in the ribosomes (28). It may also be worth mentioning that, in dystrophic hamsters, variations in the degree of phosphorylation of histone and nonhistone nuclear chromosomal proteins have been observed (29,30).…”