Phosphorylation of prostatic nuclear matrix proteins is under androgenic control

Nuclear matrix fraction was isolated from rat ventral prostatic nuclei previously incubated with [gamma-32P]ATP to label nuclear phosphoproteins with 32P. A significant portion of the radioactivity was recovered in the phosphoproteins intrinsic to the nuclear matrix fraction. At 12 h after androgen deprivation (i.e., when a significant portion of the nuclear androgen receptor was known to be depleted), the rate, but not the extent, of phosphorylation of nuclear proteins (predominantly nonhistone proteins) was markedly reduced. Nuclear matrix fraction isolated from such preparations demonstrated a profound reduction in the rate of incorporation of 32P into the matrix-associated proteins without any apparent change in the gel electrophoretic profile of these proteins. The results indicate that the cAMP-independent protein kinase activity which catalyzes the phosphorylation of nuclear matrix proteins is under androgenic control. This may be germane to nuclear matrix-associated initial events in androgen action.     

Proteolytic degradation of nuclear matrix proteins in the rat liver, Zajdela's hepatoma and hepatoma 22A in the presence of ATP

An intense proteolytic degradation of both proteins and phosphoproteins has been observed in isolated nuclear matrices from rat liver, Zajdela Hepatoma and Hepatoma 22a, incubated with NP-40, DTT and gamma-[32P] ATP being most intense in Hepatoma 22a. Practically all phosphoproteins of Hepatoma 22a nuclear matrix degraded. This implies either an extremely high proteolytic activity in the preparation or the presence of a specific to phosphoproteins protease absent from rat liver and Zajdela Hepatoma nuclear matrices.     

Characterization of the phenol soluble and insoluble nonhistone proteins of in vivo (32)P-labelled rat liver nuclei by high-resolution gel electrophoresis

The (32)P-labelling patterns of phenol soluble and insoluble nonhistone proteins of in vivo labelled rat liver nuclei freed of the soluble nuclear proteins have been determined after separation by high-resolution gel electrophoresis. The bulk of the proteins of the nuclear residues was phenol soluble. Seven percent of the proteins of the nuclear residues was obtained with the aqueous phase. As shown in this paper both fractions contain (32)P-labelled proteins but they represent different types of nonhistone proteins.     

Phosphorylation of a nonhistone protein fraction which coextracts with the high-mobility-group proteins of chromatin

³²P-labelled chromatin proteins from rat liver and ventral prostate were fractionated according to the procedure designed to enrich high-mobility-group (HMG) nonhistone proteins. This fraction, however, reproducibly demonstrated small amounts of apparently basic nonhistone proteins other than HMG nonhistone proteins. These proteins appeared to be tissue specific and were highly labelled with ³²P. The ³²P-labelled phosphoproteins were soluble in trichloroacetic or perchloric acid, migrated in acid-urea polyacrylamide gels, and demonstrated pI values ranging from 6.8 to 7.5. The HMG proteins 1 and 2 showed no incorporation of radioactivity under these experimental conditions.     

Phosphorylation and DNA binding of nuclear rat liver proteins soluble at low ionic strength.

Proteins were extracted from isolated rat liver nuclei with 0.15 M NaCl and 0.35 M NaCl at pH 8.0. The number of phosphoproteins in these extracts was determined by labeling with 32P and autoradiography after two-dimensional gel electrophoresis. Two proteins, B22p and B24p, contained small amounts of 32P and sedimented with the 30S nuclear informofer particle. With the exception of two phosphoproteins, CB and CN', all of the phosphoproteins found in the 0.35 M NaCl extract. Approximately 20% of the 0.15 M NaCl soluble proteins bound to rat liver DNA in 0.05 M KCl-0.05 M Tris-HCl (pH 8). Of these proteins, 1-2% bound to DNA in 0.15 M KCl and were eluted with 2 M KCl. This DNA bound fraction which contained both phosphorylated and nonphosphorylated proteins was similar in both the 0.15 and 0.35 M NaCl extracts. However, two major proteins (C13 and C14) and three minor proteins (C15, C25, Cg') were present only in the 0.15 M NaCl extract. The results of the present study show that there are marked similarities in the two-dimensional gel electrophoretic, phosphorylation, and DNA binding properties of rat liver nuclear proteins soluble in either 0.15 or 0.35 M NaCl.     

Concentration of particular high molecular mass phosphoproteins in rat liver nuclei and nuclear matrix decreases following inhibition of RNA synthesis by α-amanitin

Purified liver nuclei were isolated from rats treated with non-lethal doses of α-amanitin, actinomycin D, galactosamine or cycloheximide. The nuclei were incubated in the presence of adenosine 5′-[γ-³²P]triphosphate, and digested with DNAase or DNAase plus high salt concentrations to prepare nuclear residual structures. Using SDS-polyacrylamide gel electrophoresis followed by autoradiography, samples from untreated rats were shown to contain major phosphoproteins in the range 76–260 kDa, with a prominent triplet of bands with 110, 117 and 128 kDa. Treatment of animals with α-amanitin or high doses of actinomycin D and galactosamine caused a significant decrease in the concentration of a few phosphorylated species, including the 110 kDa protein in whole nuclei, and their disappearance from the nuclear matrix or residual ribonucleoprotein structures after 1–3 h. The changes were reversible, complete recovery being observed after 5 h in the case of α-amanitin. No similar results were obtained with nuclei from rats treated with the translation inhibitor cycloheximide. The data are discussed in view of a possible effect of certain high molecular mass phosphoproteins on reactions of the heterogeneous nuclear RNA/mRNA pathway in the cell.     

NONHISTONE NUCLEAR PROTEINS OF RAT BRAIN

Abstract— The rat brain was dissected into cerebral cortex, cerebellum and the remaining regions. From the nuclei, isolated from these three brain sections, were extracted two fractions of nuclear sap proteins (proteins soluble in 014 M NaCl and proteins soluble in 01 M Tris-HCl buffer pH 7-6) and two fractions of nonhistone chromosomal proteins (one soluble in 0-35 M NaCl and one which is not soluble at this salt concentration). Each of these four fractions of the nonhistone nuclear proteins was further separated by polyacrylamide gel electrophoresis. The electrophoretic patterns of the studied fractions of nuclear proteins are qualitatively identical regardless of the brain section from which the analysed protein fraction was isolated. In addition, there arc no qualitative differences in the electrophoretic patterns of nonhistone chromosomal proteins which are and which are not soluble in 0-35 M NaCl. In contrast to the qualitative similarity of the electrophoretic patterns of proteins from different sections of the brain, the amount of the nonhistone nuclear proteins is characteristic for each studied brain section. The ratio of the total nonhistone nuclear proteins to DNA is highest in the brain cortex and lowest in the cerebellum. The most expressed difference between the nuclei is in the ratio of the nonhistone chromosomal proteins soluble in 0-35 M NaCl to DNA. This ratio is 0-52 in the cortex. 0-38 in the mixture of noncortical and noncerebel-lar regions and only 0-18 in the cerebellum. The amount of the three fractions of nonhistone nuclear proteins in the nuclei of individual brain sections is proportional to the activity of the genome in these nuclei. The only exception are the nonhistone chromosomal proteins which are not soluble in 0-35 M NaCl. These proteins and the histones are present in the same amounts in nuclei isolated from all three studied sections of the brain. The results support a proposal that the nonhistone nuclear proteins are involved in the expression of the genetic activity of the cell, without the majority of the proteins in any of the four fractions being the specific regulatory molecules.     

Studies in vitro of the effects of adenosine 3'':5''-cyclic monophosphate on the phosphorylation of nuclear proteins in isolated rat heart nuclei.

Isolated rat heart nuclei were prepared by homogenization and sucrose-density-gradient centrifugation. The protein/DNA ratio of these nuclei was 3.1:1 (w/w), and the histones/non-histone proteins/DNA proportions were 1.4:1.6:1 (by wt.). Non-histone proteins were fractionated into six major groups by elution on a quaternized anion-exchanger (QAE-Sephadex A-50 column with increasing concentrations of NaCl in 5M-urea/0.01 M-Tris/HCl buffer (pH8.3). When isolated nuclei were incubated in a medium containing [gamma-32P]ATP, a differential distribution of 32P was observed in the six fractions of nonhistone proteins. The fractions eluted from the Sephadex column with 0.35M- and 0.6M-NaCl contained contained 80% of the total radioactivity incorporated into the non-histone proteins. This incorporation into the 0.35M- and 0.6M-NaCl fractions was increased by 66 and 112% respectively in the presence of cyclic AMP. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of these two particular fractions showed a selective increase in labelling of five protein bands in the presence of cyclic AMP.     

DNA-cellulose column chromatography of phosphorylated nucleolar nonhistone proteins

Summary A salt-extraction procedure was used to isolate a nucleolar nonhistone protein fraction, containing [³²P]phosphoserine, from the nucleoli of Novikoff hepatoma ascites cells. These proteins are similar in amino-acid composition to whole nuclear (chromosomal) nonhistone proteins. DNA-cellulose column chromatography showed that this fraction contains DNA-binding phosphoproteins, some of which will bind only to homologous (Novikoff) nucleolar or nuclear DNA.     

Properties of a 110000 molecular weight protein in rat liver hnRNP particles

Particles carrying heterogeneous nuclear RNA (30–40 S-particles) were isolated from rat liver nuclei and the particle proteins separated by sodium dodecylsulfate gel electrophoresis. Some properties of a 110000 molecular weight component (P 110/103) were studied in detail: (i) P 110/103 was labeled to a 4–5 times higher specific activity than the major particle proteins in the presence of [¹⁴C]-amino acidsin vivo. (ii) In nuclei incubated with [³H]- or [³²P]-nicotinamide adenine dinucleotide P 110/103 was labeled presumably by ADP-ribosylation. (iii) A protein with the same molecular weight as P 110/103 and isolated from the nuclear extract by affinity chromatography was phosphorylated in vitro.Abbreviations hnRNA heterogeneous nuclear RNA - hnRNP and mRNP ribonucleoproteins which contain hnRNA respectively mRNA     

Degradation of phosphorylated chromosomal nonhistone proteins

In experiments with in vivo 32P-labelled nonhistone proteins of rat liver nuclei it was shown that these components are more sensitive against degradation than the mass of the nonhistone proteins. In the presence of 0.1 mM phenylmethylsulfonylfluoride and 1 mM sodium molybdate, however, they are protected against degradation.     

Properties of the genome in normal and SV-40 transformed WI-38 human diploid fibroblasts. III. Turnover of nonhisone chromosomal proteins and their phosphate groups.

The turnover of nonhistone chromosomal proteins and their phosphate groups was compared in normal and in SV-40 virus transformed WI-38 human diploid fibroblasts. Cells were pulse labelled with tryptophan-³H and ³²P for 30 minutes and the specific activities of tryptophan-³H and ³²P in the various molecular weight classes of nonhistone chromosomal proteins were determined during the first four hours following termination of labelling. While a rapid turnover of high molecular weight nonhistone polypeptides (142, 000 to 200, 000 Daltons) is evident after one hour in SV_40 transformed cells, the specific activities of these nonhistone chromosomal polypeptides are not significantly decreased in normal cells. In contrast, a rapid turnover of low molecular weight (30, 000 to 51, 000 Daltons) nonhistone chromosomal proteins occurs during the first hour in normal WI-38 cells with no corresponding decrease in the specific activities of these proteins in SV-40 transformed cells. There is no apparent net turnover of phosphate groups on nonhistone chromosomal proteins in either normal or SV-40 transformed cells four hours following pulse labelling. Rather, during the first four hours significant fluctuations are observed in the ³²P specific activities of defined molecular weight fractions. Taken together with previous reports of differences in the composition, synthesis and phosphorylation of nonhistone chromosomal proteins in normal and SV-40 transformed human diploid cells the present results further indicate the complex nature of the alterations in these proteins which accompany viral transformation.     

Decrease in ADP-ribosylation of HeLa non-histone proteins from interphase to metaphase

Variations for non-histones in the ADP-ribosylating activities of interphase and metaphase cells were investigated. 32P-Labeled nicotinamide adenine dinucleotide ([32P]NAD), the specific precursor for the modification, was used to radioactively label proteins. Permeabilized interphase and mitotic cells, as well as isolated nuclei and chromosomes, were incubated with the label. One-dimensional and two-dimensional gels of the proteins of total nuclei and chromatin labeled with [32P]NAD showed more than 100 modified species. Changing the labeling conditions resulted in generally similar patterns of modified proteins, though the overall levels of incorporation and the distributions of label among species were significantly affected. A less complex pattern was found for nuclear scaffolds. The major ADP-ribosylated proteins included the lamins and poly(ADP-ribose) polymerase. Inhibitors of ADP-ribosylation were effective in preventing the incorporation of label by most non-histones. Snake venom phosphodiesterase readily removed protein-bound 32P radioactivity. A fundamentally different distribution of label from that of interphase nuclei and chromatin was found for metaphase chromosome non-histones. Instead of 100 or more species, the only major acceptor of label was poly(ADP-ribose) polymerase. This profound change during mitosis may indicate a structural role for ADP-ribosylation of non-histone proteins.     

The nuclear matrix continues DNA synthesis at in vivo replicational forks

Alkaline cesium chloride gradient analysis of in vivo [3H]bromodeoxyuridine-labeled and in vitro [alpha-32P]dCTP-labeled DNA was used to determine whether in vitro DNA synthesis in regenerating rat liver nuclei and nuclear matrices continued from sites of replication initiated in vivo. At least 70 and 50% of the products of total nuclear and matrix-bound in vitro DNA synthesis, respectively, were continuations of in vivo initiated replicational forks. The relationship of the in vitro DNA synthetic sites in total nuclei versus the nuclear matrix was examined by using [3H]bromodeoxyuridine triphosphate to density label in vitro synthesized DNA in isolated nuclei and [alpha-32P]dCTP to label DNA synthesized in isolated nuclear matrix. A minimum of about 40% of matrix-bound DNA synthesis continued from sites being used in vitro by isolated nuclei. Furthermore, nuclear matrices prepared from in vitro labeled nuclei were 5-fold enriched in DNA synthesized by the nuclei and were several-fold enriched, compared to total nuclear DNA, in a particularly high density labeled population of DNA molecules.     

Partial purification and properties of a chromatin-associated phosphoprotein kinase from rat liver nuclei.

A phosphoprotein kinase (EC 2.7.1.37) KIVb, from rat liver nuclei, was purified 75-fold by phosphocellulose chromatography and gel filtration on Sephadex G-200. The enzyme, which has an apparent molecular weight of 55 000, phosphorylates casein and chromatin-bound nonhistone proteins more readily than histones or ribosomal proteins. It exhibits an absolute requirement for divalent cation with optimum activity at 15--20 mM Mg2+. Maximal kinase activity is achieved at 100 mM NaCl. The pH vs. activity curve is biphasic with optima at pH 6.5 and pH 8.0. The Km value for casein is 280 mug/ml and the Km for ATP is 6-10(-6) M. Kinase KIVb phosphorylates numerous nonhistone nuclear proteins as shown by electrophoretic analysis. The addition of kinase KIVb to reaction mixtures containing nonhistone proteins results in the phosphorylation of a spectrum of polypeptides similar to those that are phosphorylated by endogenous nuclear kinases. Nonhistone proteins bound to chromatin appear to be better substrates for KIVb than nonhistones dissociated from chromatin. A comparison of nuclear phosphoproteins phosphorylated either in the intact animal or in vitro (by the addition of kinase KIVb) indicates some differences and some similarities in the patterns of phosphorylation.     

Identification of lamin B and histones as 1,25-dihydroxyvitamin D3-regulated nuclear phosphoproteins in HL-60 cells.

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3)-induced differentiation of HL-60 leukemia cells is accompanied by a number of cellular changes including regulation of oncogene expression and induction of terminal differentiation. We investigated the mechanism by which 1,25-(OH)2D3 induces these changes. We detected 10 nuclear phosphoproteins, designated p66, p45, p36, p33, p32, p27, p22, p19, p18 and p17, that show alterations in phosphorylation within 6-40 h of 1,25-(OH)2D3 treatment. When phosphorylation reactions were performed with isolated nuclei (in vitro), three of these proteins were phosphorylated in a calcium and phospholipid dependent manner: p66, p36, and p19 P66 was phosphorylated in response to 1,25-(OH)2D3 and purified in a manner similar to that used for nuclear lamins. Western blot analysis of 2-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels confirmed its identity as lamin B. Phosphorylation of p17 and p18 decreased following 1,25-(OH)2D3 treatment. We separated p17 and p18 by SDS-PAGE and obtained N-terminal amino acid sequence to identify these phosphorproteins as histones H2b and H3, respectively. P19 and p22 were both DNA-cellulose binding proteins whose phosphorylation was altered by 1,25-(OH)2D3 treatment. Increased phosphorylation of p27 was detected using 2-dimensional SDS-PAGE. Phosphorylation of nuclear proteins in the intact cell (in vivo), revealed increases in p66, p45, p36, and p33 phosphorylation and a decrease in p17 phosphorylation following 1,25-(OH)2D3 treatment. We detected an increase in phosphorylation of p32, which was extracted with salt from nuclei and migrated on SDS-PAGE similar to histone H1. Thus, we have identified 1,25-(OH)2D3-sensitive nuclear phosphoproteins, including lamin B and several histones. We have also detected and characterized several less abundant nuclear DNA binding phosphoproteins whose phosphorylation was affected by 1,25-(OH)2D3.     

Effect of triiodothyronine on rat liver chromatin protein kinase.

1. Injection of triiodothyronine to rats stimulates protein kinase activity in liver chromatin nonhistone proteins. A significant increase was found after two daily injections. A 4-fold increase was observed with the purified enzyme after eight daily injections of the hormone. No variations were observed in cytosol protein kinase activity. Electrophoretic pattern, effect of heat denaturation, effect of p-hydroxymercuribenzoate seem to indicate that the enzyme present in treated rats is not identical to the enzyme in control animals, which suggests that thyroid hormone has induced nuclear protein kinase. Diiodothyronine, 3, 3', 5'-triiodothyronine have no effect on protein kinase. 2. Chromatin non-histone proteins isolated from rats injected with triiodothyronine incorporated more 32P when incubated with [gamma-32P]ATP than the chromatin proteins from untreated rats. Thyroidectomy reduced the in vitro 32P incorporation. It is suggested that some of the biological activity of thyroid hormone could be mediated through its effect on chromatin non-histone proteins.     

Phosphohistidine is found in basic nuclear proteins of Physarum polycephalum

Nuclear extracts of the true slime mold, Physarum polycephalum, show protein histidine kinase activity towards exogenous histones [(1985) J. Biol. Chem. 260, 16106-16113]. Physarum microplasmodia were labeled with [32P]phosphate in vivo and two basic proteins containing alkali-stable phosphate were detected. The labeled proteins comigrated with Physarum histones H1 (approximately) and H2A and phosphoamino acid analysis showed that each protein contained [32P]-phosphohistidine. The H2A-like protein was also labeled in isolated nuclei incubated with [35S]thio-ATP. We conclude that some Physarum nuclear proteins contain phosphohistidine.     

A protein-tyrosine kinase in the nuclear matrix from rat liver

Protein kinase activity in isolated nuclei from rat liver was detected in situ after electrophoresis on SDS-polyacrylamide gel containing no exogenous protein substrate. After renaturation of polypeptides, the gel was incubated with [gamma-32P]ATP and divalent cations. Among five major protein kinase activities observed as radioactive bands by autoradiography, a protein kinase autophosphorylating on tyrosine (Mr 30,000) was identified and found to be localized in the nucleus, particularly in the nuclear matrix. The intensity of the activity band representing the level of the protein-tyrosine kinase in rat liver nuclei did not appreciably change during 3-24 h after partial hepatectomy.