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D Doenecke

Publications and source records attributed to D Doenecke.

97 records · Page 6Linked to original sources
PubMed1972

Effect of cortisol on the thiol content of rat liver nuclear proteins.

Administration of cortisol to normal or adrenalectomized rats leads within 15-30min to an increased thiol content of nuclear proteins, measured by the incorporation of iodo[(3)H]-acetate or N-[(14)C]ethylmaleimide or by colorimetric methods. The same effect is observed after incubation of isolated rat liver nuclei with corticosteroids. The increased thiol content of the nuclear proteins shows the same time-dependence as the stimulation of RNA synthesis by corticosteroids observed in vivo and in vitro. Amino acid analysis of the carboxymethylated proteins reveals that in the experiments in vivo most of the label is present as carboxymethylcysteine with small amounts of carboxymethyl-lysine and carboxymethylhistidine, whereas in the experiments in vitro more carboxymethyl-lysine and carboxymethylhistidine than carboxymethylcysteine are found. The increase in the content of thiol groups is due to cleavage of the disulphide bridges between the nuclear proteins. Polyacrylamide-gel electrophoresis of the acid-soluble fraction reveals that most of the iodo[(3)H]acetate label is incorporated into a non-histone fraction with a molecular weight of approx. 45000 whereas in the acid-insoluble fractions many protein bands are labelled.

Amino Acids↗
PubMedDate not supplied

Binding of polylysine and ethidium bromide to nucleosomal DNA: comparison of biochemical and electron microscopical results.

Ethidium bromide and polylysine interact with nucleosomal DNA and lead to change of biochemical properties and to morphological changes as to the distance between the two core particles of a nucleosome dimer. With increasing polylysine concentration, the buoyant density of nucleosomes decrease and the accessibility of the nucleosomal DNA to micrococcal nuclease is lowered. Electron microscopy of polylysine treated nucleosome dimers reveals a shortening of the internucleosomal distance as compared with controls. Treatment of nucleosomes with ethidium bromide leads to an enhanced accessibility of the nucleosomal DNA to micrococcal nuclease. Electron microscopy reveals an increase in length of the DNA connecting the two nucleosome cores in the presence of the dye. Both the binding of polylysine and the treatment with ethidium bromide apparently do not affect the histone arrangement within the nucleosome core as suggested by chemical cross-linking of histones and DNA with formaldehyde, and no obvious morphological change of the nucleosome cores can be observed.

Animals↗
PubMedDate not supplied

Round spermatids show normal testis-specific H1t but reduced cAMP-responsive element modulator and transition protein 1 expression in men with round-spermatid maturation arrest.

During spermiogenesis, histones are replaced by transition proteins, which in turn are replaced by protamines. The TNP1 gene-encoding TP1 (transition protein 1) protein contains a cAMP-responsive element (CRE) that serves as binding site for the CRE modulator (CREM). To gain further insight into the complex regulation of nucleoprotein exchanges in haploid spermatids and its potential role for spermatogenic impairment, we studied the gene expression of testis-specific histone H1t, CREM, and TNP1 in testicular biopsies from men with normal spermatogenesis (n = 20) and with round spermatid maturation arrest (n = 16). During normal spermatogenesis, H1t messenger RNA (mRNA) was present in 86.2%+/-8.7% of pachytene spermatocytes (stages III-V), whereas H1t protein was synthesized in 83.5%+/-13.0% of pachytene spermatocytes (stages III-V) and persisted in 95.2%+/-3.1% of spermatids (steps 1-5). CREM mRNA was detectable in 74.2%+/-9.4% of pachytene spermatocytes (stages IV-V) and in 78.7%+/-10.0% of spermatids (steps 1-3). CREM protein was synthesized in 81.2%+/-14.2% of spermatids (steps 1-3). TNP1 mRNA was present in 80.0%+/-13.5% of spermatids (steps 2-4), whereas TP1 protein was synthesized in 89.7%+/-5.3% of spermatids (steps 3-4). In men with round spermatid maturation arrest, spermatids only develop to step 3 of differentiation. These spermatids were devoid of both CREM and TP1 but did contain H1t. These results indicate that TP1 is likely to be an important parameter in the histone-to-protamine exchange and in the initiation of spermatid elongation. CREM is involved in the regulation of TNP1 gene expression and consequently plays a vital role in the correct differentiation step from round spermatids to mature spermatozoa.

Chromosomal Proteins, Non-Histone↗