Studies on nuclear phosphoproteins of rat ventral prostate: Incorporation of 32P from [γ-32]ATP

Systemic administration of antisense oligonucleotides simultaneously targeting CK2α and α' subunits reduces orthotopic xenograft prostate tumors in mice

CK2 is a highly conserved, ubiquitous, signal responsive protein serine/threonine kinase. CK2 promotes cell proliferation and suppresses apoptosis, and increased CK2 expression is observed in all cancers examined. We previously reported that direct injection of antisense (AS) CK2α phosphorothioate oligonucleotides (PTO) into xenograft prostate tumors in mice significantly reduced tumor size. Downregulation of CK2α in tumor cells in vivo appeared to result in overexpression of CK2α' protein. This suggested that in cancer cells downregulation of CK2α might be compensated by CK2α' in vivo, prompting us to design a bispecific (bs) AS PTO (bs-AS-CK2) targeting both catalytic subunits. bs-AS-CK2 reduced CK2α and α' protein expression, decreased cell proliferation, and induced apoptosis in cultured cells. Biodistribution studies of administered bs-AS-CK2 oligonucleotide demonstrated its presence in orthotopic prostate xenograft tumors. High dose injections of bs-AS-CK2 resulted in no damage to normal liver or prostate, but induced extensive cell death in tumor tissue. Intraperitoneal treatment with bs-AS-CK2 PTO decreased orthotopic tumor size and downregulated both CK2 mRNA and protein expression. Tumor reduction was accomplished using remarkably low doses and was improved by dividing the dose using a multi-day schedule. Decreased expression of the key signaling pathway proteins NF-κB p65 and AKT was also observed. We propose that the molecular downregulation of CK2 through bispecific targeting of the two catalytic subunits may be uniquely useful for therapeutic elimination of tumors.

Androgen and estrogen receptors in hepatocellular carcinoma and the surrounding liver in women

Androgen receptors (AR) and estrogen receptors (ER) were consecutively assayed for hepatocellular carcinoma (HCC) and the surrounding liver was removed surgically from 19 female patients. Patient age ranged from 43 to 79 years, with an average of 61 +/- 9 years. All patients had underlying liver disease (liver cirrhosis in 16, liver fibrosis in two, and chronic hepatitis in one). Seven (37%) of 19 HCC had AR ranging from 2.3 to 82.6 fmol/mg of cytosol protein. The AR titer was higher in the HCC than in the liver in these cases. Three cases also had ER. ER existed in seven (37%) tumors (range, 2.4 to 25.6 fmol/mg of protein). AR and ER were detected in 11 (65%) and ten (58%) of 17 nonneoplastic liver tissues, respectively. Serum alpha-fetoprotein (AFP) level, hepatitis B virus markers, or histopathologic types of HCC had no correlation with the presence or absence of AR or ER and their titers. Also, there was no correlation between the AR and ER positivities. Further studies are mandatory to determine the genuine role of sex hormone receptors in the development and growth of HCC in humans.

Active uptake of testosterone by androgen receptors of hepatocellular carcinoma in humans

Hepatocellular carcinoma (HCC) is more prevalent in males than it is in females, which has often been explained by the fact that alcoholism and chronic hepatitis B virus infection are more prevalent among males. The current studies, using biochemical and autoradiographic methods, verified that HCC contains higher concentrations of androgen receptors than the surrounding liver parenchyma and that extrinsically given testosterone are actively taken up by such tumors. These results may suggest that HCC is an androgen-dependent tumor and that, therefore, this tumor is more prevalent in males than it is in females.

Purification of nuclear cAMP-independent protein kinases from rat ventral prostate

Two nuclear cAMP-independent protein kinases (designated PK-N1 and PK-N2) were purified from rat ventral-prostate and liver. The yield of enzyme units was 4-5% and 7-9% for each enzyme from the prostatic nuclei and liver nuclei, respectively. The average fold purification for prostatic nuclear protein kinase N1 and N2 was 1360 and 1833, respectively. The respective average specific activity of the two enzymes towards casein was 81,585 and 110,000 nmol 32P incorporated/hr/mg of enzyme. Protein kinase N1 comprised one polypeptide of Mr 35,000 which underwent phosphorylation in the presence of Mg2+ + ATP. Protein kinase N2 comprised two polypeptides Mr 40,000 and 30,000 of which only the Mr 30,000 polypeptide was autophosphorylated. Both enzymes were active towards casein, phosvitin, dephosphophosvitin, spermine-binding protein, and non-histone proteins in vitro. Little activity was detected towards histones. Both enzymes were stimulated by 150-200 mM NaCl. MgCl2 requirement varied with the protein substrate but was between 2-4 mM for both enzymes. With dephosphophosvitin as substrate, the apparent Km for ATP for N1 protein kinase was 0.01 mM. GTP did not replace ATP in this reaction. Protein kinase N2 was active in the presence of ATP or GTP. The apparent Km was 0.01 mM for ATP, but 0.1 mM for GTP.

Androgen receptors in hepatocellular carcinoma and surrounding parenchyma

The androgen receptor content of normal human liver, hepatocellular carcinoma, and surrounding liver tissue was determined in patients with chronic liver disease. Androgen receptor was detected in all six normal livers obtained from 4 men and 2 women. The androgen receptor content in these 6 individuals ranged from 5.0 to 10.2 fmol/mg protein (Kd 10.6-31.8 X 10(-10) M). The livers from 2 patients with chronic active hepatitis and from 10 cirrhotic patients with hepatocellular carcinoma had detectable amounts of androgen receptor ranging from 2.0 to 14.8 fmol/mg protein (Kd 4.0-30.9 X 10(-10) M). Androgen receptor was found in the cytosol of 14 of 19 men with hepatocellular carcinoma. The titer ranged from 3.7 to 45.4 fmol/mg protein (Kd 3.2-21.4 X 10(-10) M). Hepatocellular carcinoma had a significantly higher concentration of androgen receptor than did the surrounding cirrhotic liver tissue. In 2 men and 1 woman, androgen receptor was detected in the cirrhotic liver but not in the tumor. In the remaining 3 men, both tumor and cirrhotic liver were negative for androgen receptor.

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.

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.

Endogenous phosphorylation in Dunning prostate tumors of rats treated with LH-RH analogues

We investigated phosphorylation in Dunning R-3327H prostate tumor tissue of untreated rats, and rats treated with the agonist D-Trp6-LH-RH and antagonist N-Ac-D-p-Cl-Phe1,2,D-Trp3,D-Arg6,D-Ala10-LH-RH. The total phosphorylation was significantly higher in Dunning tumors than in normal ventral and dorsal prostate. Incorporation of 32P into tumor tissue of rats treated with D-Trp6-LH-RH was significantly lower than in tumors from untreated animals. The tumor regression produced by LH-RH agonist appeared to be linked with changes in the pattern of tumor protein phosphorylation. Although inhibition of tumor growth also occurred after administration of the LH-RH antagonist, no significant changes in phosphorylation were observed. The dissimilarity of effects of the agonists and the antagonists on protein phosphorylation in rat prostate tumors may be related to the differences in the mechanisms of action of these two types of LH-RH analogues.

Fractionation and partial purification of rat liver nuclear protein kinases

We have fractional and partially purified several rat liver nuclear protein kinases by utilizing endogenous (nonhistone proteins) and exogenous acidic (dephosphophosvitin) and basic (lysine-rich histone) protein substrates. Three enzymes were active towards endogenous substrates, two towards dephosphophosvitin and two towards lysine-rich histone. Of the latter only one was cAMP-dependent, however, only minimal cAMP binding activity was detected. Several features of these enzyme reactions are described revealing distinct differences in the characteristics of each of these enzymes.

Phosphoproteins and protein kinase activities of ventral prostate chromatin during sexual maturation in the rat

1. In the ventral prostates of rats undergoing normal sexual development, chromatin-associated phosphokinase activities toward dephosphophosvitin and lysine-rich histones were maximal at 48 days of age, whereas phosphorylation of endogenous chromosomal proteins was greatest in the sexually mature adult. 2. Polyacrylamide gel electrophoretic analysis of chromatin proteins from these animals revealed age-dependent changes in the amount of phosphorylation of specific proteins. 3. These were most evident in highly phosphorylated H2SO4-soluble nonhistone proteins and in those nonhistones (13-16 K and 20-35 K mol. wt) which are insoluble in H2SO4.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins. V. The steroids

Since the induction of neoplastic cells by steroids has been well documented, an attempt is made to formulate a mechanism for explaining the resultant embryonic features of such tumour cells. Special emphasis is given to estrogen receptor complexes and their effect on chromatin proteins. Specifically a mechanism is presented for estradiol-17-beta and its ability to alter the gene expression (derepression) of mammary gland epithelial cells. In this model we explore the possible effects of small differences in receptor or repressor proteins associated with estrogens to translate quantitative steroid administration into qualitative cellular responses.

Acidic-phosphoprotein phosphatase activity of rat ventral prostate nuclei: apparent lack of effect of androgens

A protein phosphatase activity has been demonstrated in nuclei of rat ventral prostate utilizing 32P-labelled phosvitin as a model acidic phosphoprotein substrate. This phosphoprotein phosphatase has a pH optimum of 6.7, is unaffected by the sulphydryl protecting agent 2-mercaptoethanol, and requires a divalent cation for maximal activity. Of the various divalent cations tested, Mg2+ is the most effective in reactivating the EDTA-inhibited enzyme. The phosphatase is inhibited by sodium flouride, sodium oxalate, N-ethylmaleimide, ATP and ADP but is relatively insensitive to ammonium molybdate. Increased ionic strength of the reaction medium also causes a reduction in the enzyme activity, e.g., by 48% at 200 mM sodium chloride. The activity of the acidic phosphoprotein phosphatase did not change significantly at 48 h or 96 h post-orchiectomy when expressed per unit of nuclear protein. However, it is reduced by approx. 30% at these times after castration if based on DNA content. The decline in activity per nucleus reflects the decrease in the realtive nuclear protein content observed at 48 h or 96 h post-orchiectomy. This suggests that the decline in the phosphorylation of prostatic nuclear acidic proteins which occurs upon androgen withdrawal is not due to increased nuclear phosphatase activity.

The effect of gamma-radiation on the interaction of DNA with nuclear non-histone proteins

The interaction of nuclear sap proteins and chromatin non-histone proteins with DNA was studied by two methods: membrane filter technique and chromatography of 32P-labelled proteins on DNA-containing columns. Irradiated DNA binds a slightly greater amount of these proteins and much more firmly than the native DNA. The effect is caused by the appearance of the locally denatured sites in irradiated DNA. Irradiation of non-histone proteins disturbs their specific interaction with DNA more easily than the non-specific binding.

Testicular chromatin activation in hypophysectomized rats

Incorporation of labeled thymidine into testicular DNA of hypophysectomized rats began to increase after the administration of testosterone propionate and choriogenic gonadotrophin. While the thymidine incorporation reached maximum in 4 days, the DNA polymerase activity did not culminate until 8 days after the initiation of hormone treatment. The high molecular weight (6--8 S), presumably cytoplasmic DNA polymerase accounted almost entirely for this increase. Administration of testosterone propionate and chorionic gonadotrophin to hypophysectomized rats results in an increase of testicular RNA polymerase and chromatin templating activity. Chain elongation and initiation studies revealed that the increased templating capacity of androgen-stimulated testicular chromatin was almost entirely caused by the increase in the number of initiation sites. While the nuclear polymerase I responded relatively rapidly to hormone stimulation and reached a prominent maximum in about three days, the activity of polymerase II was more sluggish and not as prominent. The in vivo incorporation of ortho[32P]phosphate into chromosomal phosphoproteins occurred early during the androgen treatment and reached a maximum in about 20 h. The protein phosphokinase activity peaked later, approx. 72 h after the first administration of hormones.

Comparison of some properties of chromatin non-histone proteins and nuclear sap proteins

The properties of rat liver and thymus non-histone and nuclear sap proteins were compared. The distribution of total, labile-bound and 0.35 M NaCl extractable non-histone proteins from one organ on polyacrylamide-gel electrophoresis in the presence of sodium dodecylsulphate is quite similar. On electrophoresis non-labelled and 32P-labelled non-histone and nuclear sap proteins from one organ differ from one another both qualitatively and quantitatively. We did not find an appreciable difference between non-labelled non-histone proteins isolated from liver and thymus. The distribution of 32P-labelled non-histone proteins from various organs differs quantitatively rather than qualitatively. Non-labelled and 32P-labelled nuclear sap proteins from liver and thymus differ significantly. 'Free' nuclear sap proteins and the proteins of ribonucleoprotein particles from thymus nuclei contain a great quantity of identical polypeptides, whereas other polypeptides are specific to each of these protein fractions. Upon incubation of nuclei with [gamma-32P]ATP the label is incorporated into all the fractions of nuclear protein. The nuclear proteins are phosphorylated at decreasing rates in the order: labile-bound non-histone proteins greater than firmly bound non-histone proteins greater than 'free' nuclear sap proteins = proteins of ribonucleoprotein particles greater than histones. Nuclear sap and non-histone proteins contain protein kinases capable of phosphorylating both these proteins and histones. Histone phosphorylation is sharply inhibited after addition of DNA, the protein kinases of nuclear sap phosphorylating less effectively the histones complexed with DNA than the non-histone proteins. Both non-histone and nuclear sap proteins contain fractions interacting in vitro with DNA. Denatured DNA binds twice as much 32P-labelled nuclear sap proteins and a little more 32P-labelled non-histone proteins than native DNA. Denatured DNA binds non-histone and nuclear sap proteins much more effectively than native DNA. It was shown by the membrane filter technique that the major part of the nuclear sap and non-histone proteins interacting with native DNA binds to it non-specifically. A certain portion of non-histone and nuclear sap proteins interacts specifically with homologous denatured DNA. The possible role of non-histone and nuclear sap proteins in the regulation of transcription is discussed.

Presence and androgen control of an alkaline phosphatase in the nucleus of rat ventral prostate

The presence of alkaline phosphatase (EC 3.1.3.1) activity has been demonstrated in nuclei of rat ventral prostate. This enzyme activity remained after washing of isolated nuclei with 0.5% Triton X-100; an acid phosphatase initially present with the nuclear fraction was removed by this treatment. The nuclear alkaline phosphatase, examined by utilizing p-nitrophenyl phosphate as substrate, had a pH optimum of 9.5-10.3, and a broad substrate specificity: p-nitrophenyl phosphate greater than phosphothreonine greater than beta-glycerophosphate greater than phosphoserine. The nuclear phosphatase was sensitive to denaturation by heat or urea treatments and was also inhibited by Pi, L-phenylalanine, homoarginine, dithiothreitol, and EDTA. The EDTA-inhibited enzyme was maximally reactivated by Zn2+, although Mg2+, or Ca2+ were also effective at somewhat higher concentrations. Orchiectomy of adult rats resulted in an increase in the nuclear alkaline phosphatase activity (2-3-fold at 24 or 48 h postorchiectomy). A decline in the protein: DNA ratio also occurred following orchiectomy, but the increase in phosphatase specific activity was evident whether expressed per unit of protein or per unit of DNA. Testosterone replacement following orchiectomy abolished the increase in nuclear phosphatase activity. The results suggest that the prostatic nuclear alkaline phosphatase may be involved in events related to inactivation of the prostate nucleus following androgen deprivation.

The differential response of prostatic nucleolar and extra-nucleolar protein phosphokinase activities following androgen deprivation

Protein phosphokinase activities of nucleolar and extra-nucleolar compartments of rat ventral prostate nuclei were measured using the model acidic phosphoprotein, dephosphophosvitin, as substrate. Following orchiectomy, the activity in both of these fractions declined; however, the kinase activity of the nucleolus decreased at a much greater rate than that in the extra-nucleolar portion of the nucleus. Testosterone maintenance of castrated animals prevented this decline in activity. The regulation of protein phosphokinases which phosphorylate prostatic nucleolar acidic proteins may be an important mechanism in the androgen mediated activation of the nucleolus in this target tissue.

Phosphorylation of non-histone proteins in the regulation of chromosome structure and function

Non-histone chromosomal proteins are phosphorylated and dephosphorylated within the intact nucleus by two independent sets of reactions, a protein kinase reaction which transfers the terminal phosphate group of a variety of nucleoside and deoxynucleoside triphosphates to serine and threonine residues in the proteins, and a phosphatase reaction which cleaves these phosphoserine and phosphothreonine bonds and releases inorganic phosphate. Several lines of evidence are consistent with the hypothesis that the phosphorylation and dephosphorylation of these proteins is involved in gene control mechanisms, including the findings that phosphorylated non-histone proteins are highly heterogeneous and their phosphorylation patterns are tissue specific, changes in their phosphorylation correlate with changes in chromatin structure and gene acticity, addition of phosphorylated non-histone proteins increases RNA synthesis in vitro. and phosphorylated non-histone proteins bind specifically to DNA. Cyclic AMP has both stimulatory and inhibitory properties on non-histone protein phosphorylation, depending on the enzyme fraction and substrate employed A specific protein component whose phosphorylation is inhibited by cyclic AMP has been found to be associated with RNA polymerase. The cyclic AMP-induced decrease in the phosphorylation of this protein correlates with an enhancement of RNA synthesis in vitro. These results suggest that both phosphorylation and dephosphorylation of chromatin-associated proteins may be involved in the control of gene readout.

Phosvitin phosphate content. Implications for protein kinase assay

The maximal rates of the protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) reaction studied with chicken egg yolk phosvitin as substrate are dependent on the level of dephosphorylation of phosvitin. 30 per cent dephospho-phosvitin gives the optimal initial rates. With varying levels of dephosphorylation, the apparent Km for the substrate also changes in a biphasic manner. If this factor is taken into account, and a suitable adjustment is made for the concentration of dephospho-phosvitin in the reaction it is possible to achieve maximal rates for the kinase reaction with phosvitin preparations of varying levels of dephosphorylation. Such a consideration is important for comparing the results of protein kinase studies using phosvitin as the substrate.