Template-specific stimulation of RNA synthesis by phosphorylated non-histone chromatin proteins

Transcriptional inhibition by a non-histone protein from low mobility group in homologous and heterologous in vitro systems

An acidic non-histone chromosomal protein of low mobility group (LMG) with pI of 5-5.5 and molecular weight of 160 kDa (named LMG160), has been isolated from rat liver nuclei and its inhibitory effect on transcription of DNA in vitro has been detected in a heterologous prokaryotic in vitro transcription system (T7 RNA polymerase) and also confirmed in the homologous cell-free system of rat liver nuclear extract. The results indicate that in the presence of non-histone protein LMG160, in vitro RNA synthesis represses in the both systems, which can suggest a functional role for this non-histone chromosomal protein.

Dephosphorylation of nuclear non-histone proteins in submandibular glands of rats treated with isoproterenol

Protein phosphatase that removed [32P]phosphate from non-histone proteins, i.e., phenol-soluble acidic proteins, more rapidly and strongly than from histone proteins was present in nuclei of rat submandibular glands, but was not associated with chromatin. Cyclic AMP (10(-4)-10(-2) mM) stimulated the dephosphorylation of non-histone proteins, but not that of histone proteins. After a single injection of isoproterenol (IPR), the dephosphorylation of non-histone proteins in rat submandibular gland nuclei increased within 15 min, reached a maximum in 30 min and returned to normal control levels within 4 h. The stimulation of dephosphorylation of non-histone proteins induced by IPR was not observed after prior treatment of the animals with dichloroisoproterenol. The dephosphorylation of histone proteins was not affected by the injection of IPR. Stimulation of beta-adrenoceptors with IPR in rat submandibular glands resulted in increase in cyclic AMP and decrease in RNA synthesis in the tissues in the first few hours after the injection. This decrease in RNA synthesis was temporary and was preceded by the increase in cyclic AMP level and in the dephosphorylation of non-histone acidic proteins in the tissues. These results suggest that protein phosphatase in nuclei plays an important part in the events controlling RNA synthesis by regulating the state of phosphorylation of non-histone acidic proteins. In addition, the phosphatase may be regulated by a function of the cytoplasmic membranes.

In vitro secondary activation (memory effect) of avian vitellogenin II gene in isolated liver nuclei

The vitellogenin II gene is specifically reactivated in vitro (secondary stimulation, memory effect) in purified liver nuclei that had ceased to express the gene in vivo a month after the roosters had received a single injection of estradiol (primary stimulation). The in vitro reactivation depends on the addition to the nuclei of nuclear and cytoplasmic extracts from estradiol-stimulated livers, polyamines (0.1-1.0 mM), and calmodulin (0.1 mM). Under identical incubation conditions the vitellogenin gene could not be reactivated in oviduct, embryonic, and immature chicken liver nuclei. Two other genes, those for ovalbumin and lysozyme, which are regulated by estradiol in the oviduct, could not be activated in the liver nuclei. The correct initiation of vitellogenin gene transcription in the liver nuclei was tested by primer extension studies. Addition of the antiestrogen tamoxifen (0.1 microM) to the system decreased vitellogenin mRNA synthesis by about 45% without affecting total RNA synthesis. Addition of quercetin (0.1 mM) and trans-flupenthixol (0.2 mM), inhibitors of nuclear protein kinase II and calmodulin-dependent kinase, respectively, inhibited the synthesis of vitellogenin mRNA by about 55% without affecting total RNA synthesis. The inhibitory effects of the antiestrogen and the kinase inhibitors were not additive, suggesting that both classes of inhibitor act on the same target or related targets. Depleting the estradiol receptors from the cell and nuclear extracts by means of estradiol-receptor antibodies covalently bound to Matrex beads reduced the stimulation of the vitellogenin gene by 40%. We conclude that in addition to the estradiol receptor and phosphorylation of nuclear protein(s) there are additional factors responsible for the in vitro secondary activation of the avian vitellogenin II gene.

Developmental changes in the synthesis of nonhistone nuclear proteins relative to the appearance of a short nucleosomal DNA repeat length in cerebral hemisphere neurons

Fluctuations in the pattern of synthesis of nonhistone nuclear proteins were noted in cerebral hemisphere neurons during early postnatal development of the rat. Noteworthy changes included the synthesis of an acidic nuclear protein of relative molecular weight 41,000 (41K), two chromatin-associated basic proteins (37K and 38K) and several high molecular weight chromatin acidic proteins. These changes in the synthesis of nonhistone nuclear proteins occur at a developmental stage when a short nucleosomal DNA repeat length has appeared in cerebral hemisphere neurons.

Evidence for polyphosphate in phosphorylated nonhistone nuclear proteins

Structural studies of eucaryotic nuclear proteins have revealed the presence of bound polymeric phosphates. 32P-labeled and nonlabeled nonhistone nuclear proteins (NHPs) were isolated from rat liver nuclei and subjected to various controlled hydrolytic conditions. The analysis of protease-trypsin limit peptides revealed the presence of six phosphorylated, homogeneous fragments with phosphate/amino acid molar ratios greater than unity, ranging from 1.3 to 79. Alkaline beta elimination of phosphoester bonds released polymeric phosphates with chain lengths from 2 to over 200, as determined by using two-dimensional chromatographic analysis. The identity of these labeled polymeric phosphates was established to be polyphosphate by a number of criteria, including chromatographic mobility, gravimetric precipitation to constant specific activity, generation of orthophosphate on hydrolysis, and the determination of the delta H of hydrolysis of phosphoanhydride bonds. The evidence suggests that, in addition to the phosphomonoesters of serine and threonine, multiple phosphoanhydride linkages can result in the formation of polyphosphorylated NHPs. Previous investigators have demonstrated that exogenous, free polyphosphate causes destabilization of chromatin and enhancement of transcription in vitro. Although the function of the polyphosphorylated NHPs is currently unknown, such findings have possible functional implications with regard to the postulated role of NHPs as positive modifiers of gene expression.

Gene control by phosphoproteins: a theoretical model for eukarotic DNA regulation

Although gene regulatory mechanisms in eukaryotic cells are complex, some progress is being made in understanding them. Chromosomal proteins may play a significant role in genome function and gene control. More specifically, a central role may be played by the nuclear nonhistone proteins. It appears that both viral transformation and steroid hormone action may be associated with the phosphorylation of these proteins. Recent studies have revealed that some oncogenic viruses are capable of producing viral transforming proteins with protein kinase activity. This suggests how they may subvert normal gene regulatory mechanisms. Furthermore, the effects of the steroid-receptor complex on nuclear nonhistone proteins may be similar to the effects of these viral transforming proteins, but in a controlled sense. A model of gene-regulatory, nuclear phosphorylation reactions is formulated which suggests how some oncogenic viruses may control normal gene regulatory mechanisms and how steroid hormones may interact with these same mechanisms. Such a model may reveal how disruption of these same mechanisms leads to carcinogenesis.

Gene control by phosphoproteins: a theoretical model for eukaryotic DNA regulation

Although gene regulatory mechanisms in eukaryotic cells are complex, some progress is being made in understanding them. Chromosomal proteins may play a significant role in genome function and gene control. More specifically, a central role may be played by the nuclear nonhistone proteins. It appears that both viral transformation and steroid hormone action may be associated with the phosphorylation of these proteins. Recent studies have revealed that some oncogenic viruses are capable of producing viral transforming proteins with protein kinase activity. This suggests how they may subvert normal gene regulatory mechanisms. Furthermore, the effects of the steroid-receptor complex on nuclear nonhistone proteins may be similar to the effects of these viral transforming proteins, but in a controlled sense. A model of gene-regulatory, nuclear phosphorylation reactions is formulated which suggests how some oncogenic viruses may control normal gene regulatory mechanisms and how steroid hormones may interact with these same mechanisms. Such a model may reveal how disruption of these same mechanisms leads to carcinogenesis.

Hypothesis: is viral transformation mediated by alterations in chromosomal proteins?

Efforts to clarify the mechanisms of viral carcinogenesis have been hampered, no doubt, by the lack of understanding of the complex gene-regulatory processes in the eukaryotic genome. However, numerous investigators have produced enlightening information concerning potential gene-regulatory, nuclear phosphorylation reactions. In addition, equally interesting studies involving transforming viruses have revealed that some viral products responsible for transformation have an associated protein kinase activity. These similar biochemical processes may suggest how some transforming viruses could subvert normal gene-regulatory processes.

Substrate specificity studies on a calf thymus nuclear phosphoprotein kinase

1. The protein kinase activity associated with the phosphoprotein fraction of calf thymus nuclei has been examined for its ability to phosphorylate exogenous phosphoprotein substrates. beta-Casein and phosvitin are both efficient phosphate acceptors. Phosphorylation of alpha s1 and beta-caseins was shown, directly, to occur at threonyl-49 and threonyl-41 respectively. Both threonyl residues occur within the sequence Thr-Glu-Asp. 2. alpha s1-Casein becomes a much better substrate for the kinase when partially dephosphorylated. A similar response is shown by a phosphopeptide containing the alpha s1-casein phosphate cluster and is due to a new phosphorylation site becoming available. Efficient phosphorylation of beta-casein requires that the phosphate cluster (residues 15-19) be intact and results are presented which are consistent with there being a similar requirement for phosphorylation of the site created in alpha s1-casein by partial dephosphorylation. 3. Comparison of genetic variants of beta-casein as phosphate acceptors for the kinase shows that the presence of lysyl residues close to the phosphorylation site markedly depresses the rate of phosphorylation. Maleylation of beta-casein increases the rate of phosphorylation for all of the variants tested, although to varying extents. Treatment of maleylated beta-casein with trypsin to remove the N-terminal phosphopeptide inhibits phosphorylation by the kinase. 4. The structural determinants of beta-casein allowing it to be efficiently phosphorylated by the kinase are concluded to be the presence of a sequence surrounding the phosphorylation site, which is rich in acidic amino acid residues and from which basic residues are absent. The acidic phosphate cluster of beta-casein also promotes phosphorylation either by interacting directly with the enzyme or through its influence on the conformation of beta-casein.

Characterization of a non-histone chromosomal protein which stimulates RNA polymerase II

A non-histone chromosomal protein was extracted and purified 177-fold from rat liver nuclei which stimulated RNA synthesis in vitro catalyzed by wheat germ RNA polymerase II with either liver chromatin, or native or denaturated calf thymus DNA as template. The stimulatory non-histone chromosomal protein fraction was characterized as having a molecular weight of 66 000 and a pI = 8.2--9.0. No activity was found with Escherichia coli RNA polymerase and liver chromatin. The binding of the stimulatory non-histone chromosomal protein occurred exclusively with the chromatin template and not with RNA polymerase II as assessed by its interference with actinomycin D but not with alpha-amanitin, respectively.

Regulation of transcription by DNA-bound non-histone nuclear proteins

Purified non-histone proteins from mouse mammary cells bind specifically to homologous DNA or chromatin. Complexes of non-histone protein with DNA or chromatin, isolated on agarose columns, were transcribed with both Escherichia coli RNA polymerase and RNA polymerase B from calf thymus. The fact that complexing of DNA with non-histone proteins increases transcription by E. coli RNA polymerase but not by RNA polymerase B suggests different mechanisms of transcription by these two enzymes. Similar experiments with mouse and Drosophila chromatin indicate that non-histone proteins specifically stimulate the transcription of mouse chromatin by RNA polymerase B. Non-histone proteins stimulate the transcription of mouse mammary tumor virus sequences in chromatin by RNA polymerase B but not by E. coli RNA polymerase. We conclude that those non-histone proteins bound specifically to chromatin are able to activate the transcription of specific genes by eukaryotic RNA polymerase.

Translocation of cytosol protein kinase into nuclei and the induction of tyrosine hydroxylase in NBD-2 neuroblastoma cells

Exposure of neuroblastoma cells (NBD-2) to 8-bromo-adenosine 3',5'-cyclic monophosphate (0.2-1.0 mM) (8-Br-cAMP) for 15 min caused a long term increase in the Vmax of tyrosine-3-monooxygenase activity (TH) beginning about 1 day after 8-Br-cAMP application. Cyclic AMP-dependent histone kinase was maximally activated in about 30 min and stayed activated above pretreatment levels for one hour. In cells exposed to 8-Br-cAMP for 15 min, separation of soluble and particle bound histone kinase showed that the total histone kinase activity in the soluble fraction decreased by 40%. This decrease was accompanied by an increase in protein kinase activity in the particulate fraction, suggesting enzyme translocation. After translocation, the enzyme appears to acquire a different substrate affinity because it prefers as a PO43- acceptor, acidic protein rather than histone. In NBD-2 cells this kinase appears to precede, and may be related to, the delayed increase in TH Vmax.

Non-histone chromatin proteins of B lymphocytes stimulated by lipopolysaccharide. II. Phosphorylation

Stimulation of mouse lymphocytes with the B lymphocyte specific mitogen lipopolysaccharide results in an increased rate of phosphorylation of non-histone chromatin proteins. An initial small increase in phosphorylation occurs during the first 2 h and a much larger increase after 24 h of culture with mitogen. The phosphorylated nuclear and cytoplasmic proteins were analysed by polyacrylamide gel electrophoresis and the stimulation index of each prominent peak measured. It was inferred that selective stimulation of the phosphorylation of individual proteins had occurred from: (1) the range of stimulation indices for different proteins, and (2) the appearance, after 8 h stimulation of an apparently newly phosphorylated non-histone chromatin protein of molecular weight 115 000. The pool size of ATP was monitored and showed only small changes during the first 24 h of exposure to lipopolysaccharide. Phosphatase activity was found to be associated with lymphocyte chromatin and nucleoplasm and may help to regulate the level of phosphorylation of non-histone chromatin proteins in vivo. To preserve phosphorylated proteins during their isolation phosphatase activity was inhibited by Na2MoO4. The selective changes in phosphorylation of nuclear proteins precede, and continue during, the stimulation of immunoglobulin and DNA synthesis. Our results are thus consistent with the hypothesis that phosphorylation of non-histone chromatin proteins plays a role in the regulation of gene expression in B lymphocytes.

Non-histone chromatin proteins of B lymphocytes stimulated by lipopolysaccharide

The synthesis of non-histone chromatin proteins and nucleoplasmic proteins has been followed during lipopolysaccharide-induced division and differentiation of murine B lymphocytes. Synthesis was measured by pulse labelling with [3H]leucine, extraction of proteins was under conditions designed to prevent proteolysis and analysis of labelled proteins was by polyacrylamide gel electrophoresis. The average specific activity of non-histone chromatin proteins increased 3-fold, to a maximum, after culture for 24 h with lipopolysaccharide. Comparison of the relative synthesis of individual proteins (stimulation index) reveals three distinct responses: (1) those in the largest group show low stimulation indices, generally less than two; (2) a group of four proteins have indices between 4 and 5; (3) two proteins (molecular weights 21 000 and 22 000) both show an index of 5 at 24 h rising to between 7 and 8 by 48 h when the average specific activity is falling, coinciding with the period of rapid differentiation to high rate IgM secretion. Additionaly at this time, a newly labelled protein (Mr = 36 500) appears in the nucleoplasm followed by a second protein (Mr = 63 000) appearing between 48 and 72 h. The patterns of change are consistent with an overall increase in non-histone chromatin proteins synthesis, necessary for cell division, with superimposed specific changes in synthesis of non-histone chromatin proteins which could be related to regulation of cell differentiation.

Comparison of transcription stimulating, phenol-soluble non-histone chromosomal proteins in normal rat liver and transplantable hepatocellular carcinomas

The non-histone chromosomal proteins (NHCP) of a rapidly and slowly proliferating transplantable hepatocellular carcinoma (THC) were compared to those of normal and regenerating rat liver. The total quantity of NHCP is approximately threefold higher in the THCs than in either normal rat liver at 4 h and 44 h regenerating rat liver. Only those NHCP that can be extracted from chromatin by 0.35 M NaCl were further examined and it was observed that the proteins of this highly complex fraction could be further fractionated by their differential phenol-solubility. The phenol-soluble 0.35 NHCP contained protein(s) capable of stimulating the level of DNA-directed RNA synthesis in vitro. The total amount of this stimulatory activity was 5 times higher in the rapidly growing THC and 1.6 times higher in the slowly growing THC than in normal rat liver. In order to assess the contribution of cell-cycle dependent alterations on the increase in the amount of stimulatory activity in the THCs, 44 h regenerating rat livers were examined. This tissue represents a mix of cells in various stages of the cell cycle which is similar to that found in the THCs. It was found that the total quantity of NHCP in the 44 h regenerating rat liver was the same as in normal rat liver. The total amount of the stimulatory activity also was similar in both the normal and 44 h regenerating rat liver. The amount of the stimulatory activity was found to double in 4 h regenerating rat liver, however. These data suggest that the alterations observed in the NHCP of the THCs are not due solely to cell cycle dependent changes, but may represent malignancy dependent alterations.

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

We examined incorporation of 32P 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 32P 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 phosphorylation 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.

Characterization of protein kinases from adrenal medulla. A study of cytosol and nuclear enzymes

Since phosphorylation of chromosomal proteins by cyclic AMP-dependent protein kinases (EC 2.7.1.37) enhances template activity of adrenal medulla chromatin (9), we have studied the properties and regulation of protein kinases isolated from chromaffin cell cytosol and nuclei. DEAE-cellulose chromatography revealed three peaks of kinase activity in the nucleus (nPKI, nPKII, nPKIII) and two in the cytosol (cPKI, cPKII). The three nuclear enzymes, as well as cPKII, did not require cyclic AMP to express their catalytic activity. nPKI and nPKIII preferred acidic substrates as PO3-4 acceptors, while nPKII and the cytosol enzymes preferred basic PO3-4 acceptors. Enzyme recombination experiments using protein kinase regulatory subunits from cytosol suggested that cPKII was the catalytic subunit of cPKI. In contrast, the nuclear enzymes were not catalytic subunits of the cyclic AMP-dependent protein kinase in the cytosol (cPKI). Only the cytosol protein kinases could be inhibited by endogenous heat-stable protein kinase inhibitors. The nuclear and cytosol cyclic AMP-independent protein kinases were distinguishable on the basis of their sedimentation constants as well as Mc2+ and Mn2+ requirements.

Protein which interacts with a stimulatory factor of RNA polymerase II of Ehrlich ascites tumor cells

When partially purified Ehrlich ascites tumor RNA polymerase II was further purified on a column of phosphocellulose, stimulation of its catalysis of RNA synthesis by stimulatory factor S-II was greatly decreased. This decrease in sensitivity to the stimulatory factor was reversible: the enzyme eluted from phosphocellulose became sensitive to the factor when mixed with a protein fraction eluted from the phosphocellulose at high salt concentration. Evidence was obtained that this protein, named helper protein, binds, to the enzyme eluted from phosphocellulose, causing it to recover sensitivity to stimulatory factor S-II.

Purification and properties of a nuclear protein kinase from rat mammary gland

A nuclear protein kinase that shows a high degree of substrate specificity for the phosphorylation of the acidic proteins casein, phosvitin and non-histone chromatin proteins, rather than the basic proteins histones and protamine, was partially purified from lactatingrat mammary gland. The enzyme is associated with the acidic protein fraction of chromatin. Nuclear kinase requires Co(2+) for activity, and other bivalent cations such as Mg(2+) and Mn(2+) can substitute partially for Co(2+). The kinase is further activates (2-3-fold) by various salts, their concentration for maximum stimulation being: NaCl, 150mm; KCl, 200mm; sodium acetate, 300mm. The sedimentation coefficient of the nuclear kinase is 8.9S and its mol.wt. is approx. 300000 by gel-exclusion chromatography. The enzyme is not activated by cyclic AMP or cyclic GMP and is inhibited neither by the regulatory subunit of mammary cyclic AMP-dependent protein kinase nor by the heat-stable protein kinase inhibitor from ox heart. Analysis of (32)P-labelled protein products reveals that the kinase transfers the terminal phosphate of ATP to serine and threonine residues of proteins. The enzyme, however, has specificity for the phosphorylation of threonine in casein and serine in phosvitin. Molecular size and enzymic characteristics of the nuclear protein kinase are clearly different from those of the cytosol enzyme previously characterized.

Stimulation of synthesis of the proteins of 30-S nuclear ribonucleoprotein particles in human amnion U cells by viral infection

Early increase in RNA synthesis induced in human amnion U cells by infection with poliovirus is accompanied by an increased incorporation of amino acids into non-histone nuclear proteins with an approximate molecular weight of 40 000. These proteins are the main polypeptides of the 30-S nuclear ribonucleoprotein particles. After fractionation of nuclear proteins by extraction with solutions of different ionic strength, these polypeptides are present in the fraction of nuclear sap proteins soluble in 0.1 M Tris - HCl buffer, pH 7.6, and in the fraction of non-histone chromosomal proteins which are soluble in 0.35 M NaCl. The increase in synthesis of non-histone nuclear proteins with an approximate molecular weight of 40 000, observed in the infected cells, represents an increase in the synthesis of proteins concerned with post-transcriptional events and, therefore, is the result and not the cause of gene activation.

Some effects of chlorambucil on nuclear protein phosphorylation in the Yoshida ascites sarcoma

The ability of nuclei, isolated from Yoshida ascites sarcoma cells, to phosphorylate nuclear proteins in the presence of [gamma-32P]ATP has been investigated. Comparisons were made between a strain sensitive to the effects of the alkylating agent, chlorambucil, with a corresponding resistant strain both before and after drug-treatment of tumour-bearing animals. There was no gross quantitative differences between the drug-sensitive and-resistant untreated cells but treatment resulted in increased levels in the sensitive strain. Qualitative differences were seen before treatment in the phosphorylation pattern of the tris-saline-soluble nuclear sap fraction. The high molecular weight species in the fraction from sensitive cells showed phosphorylations which were absent, or present at very low levels, in the corresponding fraction from drug-resistant cells. Changes were observed in the tris-saline-soluble and non-histone protein fractions from drug-sensitive cells following treatment of tumour-bearing animals. Only minor alterations in patterns of phosphorylation were seen in fractions from drug-resistant cells.

A protein cofactor that stimulates the activity of DNA-dependent RNA polymerase I on double-stranded DNA

Partially purified rat liver RNA polymerase I chromatographed on ribosomal RNA-Sepharose loses most (96%) of its activity assayed on native calf-thymus DNA templates, but loses little (8%) of its activity assayed on poly(deoxycytidylic acid) template. Polymerase I is not stimulated by polymerase II protein factor, or by bovine serum albumin. However, it is stimulated by histones, polylysine, and spermine. Addition of a protein fraction eluted by high ionic strength from the rRNA-Sepharose also restores activity on native calf-thymus DNA. Further purification yields a fraction containing two proteins of 11 000 and 12 000 molecular weight. Both proteins are distinct from histones by electrophoresis in sodium dodecyl sulfate and in acid urea. Both proteins are basic, insensitive to heat, bind to DNA, and stimulate polymerase I activity. The degree of stimulation of polymerase I is dependent upon both the enzyme/DNA and the factor/DNA ratio. The protein factors also stimulate polymerase II activity about half as effectively as polymerase I.

Assembly of DNA with histones and nonhistone chromosomal proteins in vitro

We have examined, by protein binding assays, thermal denaturation, and circular dichroism, the possible effects of histones on nonhistone chromosomal protein (NHCP) interactions with DNA. For these studies, we have fractionated mouse Krebs II chromosomal proteins into three discrete fractions: Mo, 5 M urea-soluble NHCP; M1, 5 M urea-1 M NaCl-soluble NHCP from 5 M urea-extracted chromatin; and M3, 5 M urea-3 M NaCl-soluble chromosomal proteins from 5 M urea-1 M NaCl-extracted chromatin. These fractions contain heterogeneous populations of NHCP, and were found to differentially affect histone binding to DNA by methods of reconstitution, or by direct binding of M0, M1, or M3 to urea-salt reconstituted DNA with histones. M0 was found to exert a unique effect on the thermal denaturation and circular dichroic spectra of DNA-histone complexes. M0 from Krebs II chromatin was also found to complete for DNA sites in the presence of M0 from mouse liver chromatin. In addition, in 5 M urea, pH 8.0, histone binding to DNA reached saturation at 1.85 mg/mg of DNA, higher than the in vivo ratio of 1.00 mg/mg of DNA. Saturation of histone binding to DNA occurred only in the presence of 5 M urea, resulting in a reduction of nonspecific histone-histone interactions on DNA.

Enhanced template activity in chromatin from adrenal medulla after phosphorylation of chromosomal proteins

Translocation of protein kinase to the nucleus had been implicated earlier in the transsynaptic control of gene expression mediated by cholinergic nerves in adrenal medulla. Phosphorylation of chromosomal proteins by adenosine 3',5'-monophosphate-dependent protein kinase and adenosine 3',5'-monophosphate enhances the template activity of chromatin from adrenal medulla. When homologous RNA polymerase II is used the relative activation is greater than that obtained with Escherichia coli RNA polymerase. The substrate for such phosphorylation does not seem to be RNA polymerase II. Phosphorylation of specific acidic protein probably mediates this enhancement of template activity.