Control of histone acetylation : Cell-cycle dependence of deacetylase activity in Physarum nuclei

Nuclei from naturally synchronous plasmodia of Physarum polycephalum were assayed for histone deacetylase activity. The substrate for the assay was a peptide comprising the amino terminal region (residues 1–23) of calf thymus histone H4. The deacetylase activity per nucleus remained constant during S phase and early G2 phase and then doubled in a linear fashion during mid and late G2 phase reaching its maximum level at metaphase. The data imply that H4 acetylation is linked to prior chromatin structural changes.     

Cell-cycle dependence of dolichyl phosphate biosynthesis

The cell-cycle dependence of dolichyl phosphate biosynthesis has been investigated in mouse L-1210 cells fractionated by centrifugal elutriation. Dolichyl phosphate levels increased linearly through the cell cycle, reaching a value in late S phase twice that of early G1. The cell-cycle dependences of four dolichyl phosphate metabolizing enzymes have been measured: cis-prenyltransferase, CTP-dependent dolichol kinase, dolichyl phosphatase, and dolichyl pyrophosphatase. The kinase, the cis-prenyltransferase, and the pyrophosphatase showed cell-cycle variations, increasing through G1 to a maximum in S phase while the monophosphatase activity was cell-cycle independent. The rate of accumulation of dolichyl phosphate was not affected by growing the cells in mevalonolactone-supplemented media. The evidence presented is consistent with models in which either the cis-prenyltransferase or the kinase/phosphatase couple (or both) regulates the levels of dolichyl phosphate in the cell.     

Calf liver nuclear N-acetyltransferases. Purification and properties of two enzymes with both spermidine acetyltransferase and histone acetyltransferase activities.

Calf liver contains two nuclear N-acetyltransferases which are separated by chromatography on hydroxylapatite. Both acetyltransferase A and acetyltransferase B will transfer acetate from acetyl-CoA to either histone or spermidine. The same protein catalyzes the reaction with both substrates; this is shown by a constant ratio of spermidine to histone activity over a 5,000-fold purification and identical heat denaturation kinetics for both spermidine and histone acetyltransferase activity with each enzyme. Histone is preferentially acetylated when both acceptors are present. Both enzymes preferentially acetylate polyamines (spermidine, spermine, and diaminodipropylamine) to diamines. Acetyltransferase A acetylates histones in the order: whole histone greater than H4 greater than H2A greater than H3 greater than H2B greater than H1; acetyltransferase B in the order: whole histone greater than H4 = H3 greater than H2A greater than H2B greater than H1. Michaelis constants are 2 X 10(-4)M for spermidine and 9 X 10(-6)M for acetyl-CoA. Acetyltransferase A has a molecular weight of 150,000; acetyltransferase B 175,000. Both enzymes are strongly inhibited by p-chloromercuribenzoate and weakly inhibited by EDTA.     

Casein kinase II is a predominantly nuclear enzyme

Casein kinase II (CK II) has been implicated in regulating multiple processes related to cell growth, proliferation, and differentiation. To better understand the function(s) and regulation of this ubiquitous kinase, it is important to know its subcellular distribution. However, this issue has been the subject of contradictory reports. In this study, we have used indirect immunofluorescence microscopy and cell fractionation to study the subcellular distribution of all three subunits of chicken CK II, alpha, alpha', and beta. We examined primary chick embryo fibroblasts, virally transformed chicken hepatoma cells, as well as HeLa cells transiently transfected with cDNAs encoding chicken CK II subunits. We found that each of the three CK II subunits was located predominantly in the cell nucleus, irrespective of the cell type analyzed or the procedure used for cell fixation. No major differences were detected in the subcellular distributions of individual CK II subunits, and no evidence was obtained for subunit redistributions during interphase of the cell cycle. During mitosis, the bulk of the enzyme was dispersed throughout the cell, though a fraction of all three subunits was associated with the mitotic spindle. Biochemical studies based on mechanical enucleation of chicken cells confirmed the predominantly nuclear location of all three CK II subunits. Finally, immunoblotting experiments were carried out to study the expression of CK II subunits. A survey of different adult chicken tissues revealed substantial tissue-specific differences in the levels of CK II protein, but no evidence was obtained for pronounced tissue specificity in the expression of individual CK II subunits. These results strongly suggest that CK II functions primarily in regulating nuclear activities, and that the two catalytic subunits, alpha and alpha', may carry out overlapping functions.     

Cell-cycle dependence of heat-induced interphase death in mouse L5178Y cells.

Cell lysis and eosin staining were observed in L5178Y cells within the first 3 h of post-hyperthermia incubation at 37 degrees C, after which both leveled to a plateau. Lysis and eosin staining were proportional to the severity of heat in asynchronous cells, whereas it was maximum in the most heat-sensitive M phase, intermediate in S, and least in heat-resistant G1 for the same heat treatment. Further, leakage of labeled [3H]thymidine and a decrease in radioactivity retained within heated cells coincided with an increase in eosin staining, indicating that the dye uptake was due to membrane damage. It was presumed that the eosin-stained fraction represented dead cells. The percentage eosin-stained cells reached a plateau, and this level was used to determine survival; when the results were compared with those obtained by the colony formation method, they were identical. By comparing the two survival assay methods we concluded that cell death after hyperthermia in L5178Y cells is mainly by interphase death in all phases of the cell cycle. The reasons for this conclusion are that a reduction in survival could be detected within one generation of L5178Y cells by the eosin staining method, and the survival values obtained by this method were identical to those obtained by the colony formation method.     

Phosphorylation and protein kinase activities of chromosomal non histone proteins from chick embryo fibroblasts.

Confluent chick embryo fibroblasts were cultured in vitro in (i) medium which prevented the cells from dividing, (ii) medium which stimulated the cells to divide synchronously, (iii) medium without lysine in which the cells were blocked in G1. Chromosomal non histone proteins (NHP) were extracted from cells pulse labelled with 32P phosphate, and the radioactivity analyzed by acrylamide gel electrophoresis. Several radioactive peaks were found all along the gel in the NHP from confluent and stimulated cells. The highest phosphorylation was found in the fast moving proteins, but the stimulation of the cells increases the phosphorylation of the slower moving proteins. In the NHP from cells cultured in the medium without lysine only the slow migrating proteins were phosphorylated. NHP were extracted from unlabelled cell cultures in the three different media, incubated with [gamma-32P] ATP and analyzed by acrylamide gel electrophoresis. Highly labelled peaks were observed in the fast moving proteins from stimulated cells and from cells cultured in a medium deprived from lysine. By comparing in vivo and in vitro phosphorylation, it can be concluded that in confluent cells the turnover of bound phosphate is slow. In stimulated cells there is a fast turnover of the phosphate bound to fast turnover of the phosphate bound to a small group of fast migrating proteins and very little turnover of the phosphate bound to slow migrating proteins. The cells were incubated with labelled lysine and NHP analyzed by gel electrophoresis. The radioactivity of individual NHP varied with the culture conditions, but in all cases, there was little radioactivity in the fast moving proteins. The phosphate groups submitted to a fast turnover are bound to stable proteins. Phosvitin and casein kinase activities were measured in the NHP fractions. Nine-ten peaks of activities were observed with each substrate. Some variations were observed which apparently correlate with the culture conditions.     

Purification and characterization of two porcine liver nuclear histone acetyltransferases

Two forms of porcine histone acetyltransferase (types I and II) have been purified to apparent homogeneity from liver nuclei. Both activities are extracted from nuclei by 0.5 M NaCl and display a native Mr of 110,000 as determined by gel filtration. Saline enzyme extracts were subject to ammonium sulfate precipitation and sequential chromatography on Q-Sepharose, Sephacryl S-200, hydroxylapatite, and Mono Q supports. The histone acetyltransferase type I fraction contains three polypeptide chains with apparent Mr values of 105,000, 62,000, and 45,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cyanogen bromide peptide mapping and immunoblotting suggest that the Mr 62,000 and 45,000 polypeptides are derived by cleavage of the Mr 105,000 polypeptide. Histone acetyltransferase type II contains two different subunits with apparent Mr values of 50,000 and 40,000, respectively. The amino acid composition, heat inactivation profiles, and Michaelis constants with respect to both acetyl coenzyme A and histones were indistinguishable for types I and II. However, affinity-purified polyclonal antibodies to both forms of the enzyme do not cross-react; cyanogen bromide-derived in situ cleavage digest patterns show few similarities; and the turnover number for type I is approximately 15-fold lower than that for type II. We estimate that there is one enzyme molecule for every 500 nucleosomes. The existence of two distinct forms of nuclear histone acetyltransferase in pig liver suggests that they may have separate functions in vivo.     

Role of cadmium in activating nuclear protein kinase C and the enzyme binding to nuclear protein.

Specific effects of cadmium on nuclear protein kinase C activity were found with 3T3/10T1/2 mouse fibroblast and rat liver nuclei. Treatment of the mouse fibroblasts in culture with 12-O-tetradecanoylphorbol-13-acetate resulted in the stimulation of nuclear protein kinase C activity in a "fixed" pool which is defined by its resistance to chelator extraction, whereas the chelator extractable enzyme activity, defined as the "labile" pool was unaffected. Cadmium was found to potentiate the effect of the phorbol ester, directed specifically to nuclei, since the particulate protein kinase C activity was not changed under similar treatment. In a reconstituted system consisting of rat liver nuclei and rat brain protein kinase C, cadmium stimulated the binding of the enzyme to a 105-kDa nuclear protein. The binding of a 105-kDa protein to protein kinase C is attributed strictly due to the cadmium effect, whereas a 50-kDa protein binding to protein kinase C was only enhanced by cadmium. We propose a mechanistic model, where cadmium substitutes zinc in the regulatory domain of protein kinase C rendering the putative protein-protein binding site exposed.     

Protein kinase C-related kinase targets nuclear localization signals in a subset of class IIa histone deacetylases

Class IIa histone deacetylases (HDACs) -4, -5, -7 and -9 undergo signal-dependent nuclear export upon phosphorylation of conserved serine residues that are targets for 14-3-3 binding. Little is known of other mechanisms for regulating the subcellular distribution of class IIa HDACs. Using a biochemical purification strategy, we identified protein kinase C-related kinase-2 (PRK2) as an HDAC5-interacting protein. PRK2 and the related kinase, PRK1, phosphorylate HDAC5 at a threonine residue (Thr-292) positioned within the nuclear localization signal (NLS) of the protein. HDAC7 and HDAC9 contain analogous sites that are phosphorylated by PRK, while HDAC4 harbors a non-phosphorylatable alanine residue at this position. We provide evidence to suggest that the unique phospho-acceptor cooperates with the 14-3-3 target sites to impair HDAC nuclear import.

Structured summary

MINT-7710106:HDAC5 (uniprotkb:Q9UQL6) physically interacts (MI:0915) with PRK2 (uniprotkb:Q16513) by pull down (MI:0096)     

Multiple nuclear protein kinase activities in rat liver and hepatoma 3924A.

Multiple protein kinase activities were isolated from nuclei of rat and hepatoma 3924A, and purified 40- to 140-fold, respectively. Hepatic protein kinase-I exhibited high activity with casein as substrate, but was relatively inactive with either liver and hepatoma chromatin or mixed histone. In contrast, hepatoma protein kinase-I showed equivalent activity with casein and liver chromatin. Protein kinase-IIA, -IIB and-IIC from both tissues were more active with liver chromatin in comparison to casein and hepatoma chromatin, and exhibited similar electrophoretic profiles of 32P-chromatin.     

Mechanism of action of cyclic AMP-dependent histone kinase. Substrate specificity of the catalytic enzyme unit]

Interaction of several nucleotide derivates with homogenous catalytic subunit of cyclo-AMP-dependent histone kinase from pig brain is studied. Inhibition constants of these compounds are calculated, and the affinity of inhibitors to the enzyme active site is evaluated. The nature of heterocyclic base is found to be the main contribution into binding with substrate. The enzyme specificity with respect to a number of bivalent metal ions is studied, and Mg2+ is demonstrated to be the only efficient enzyme activator. It is shown by means of stationary kinetics that histone kinase-catalysed phosphotransferase reaction has a "ping-pong"-like mechanism.     

Variable dependence on protein kinase stimulatory modulator for cyclic GMP stimulation of histone phosphorylation by rat liver cyclic GMP-dependent protein kinase.

Various histone fractions from several sources differ markedly in their degree of dependence on protein kinase stimulatory modulator for maximum phosphorylation by rat liver cyclic GMP-dependent protein kinase in the presence of cyclic GMP. DEAE-cellulose and QAE-Sephadex chromatography of arginine-rich and mixed histones resulted in the histones displaying increased dependence on the modulator. This increased dependence was apparently due to the removal of contaminating modulator as heat-stable modulator activity could be eluted from the DEAE-cellulose column. Lysine-rich histone was not markedly dependent on the modulator before or after QAE-Sephadex chromatography.     

Clathrin-coated vesicles contain two protein kinase activities. Phosphorylation of clathrin beta-light chain by casein kinase II

Incubation of clathrin-coated vesicles with Mg2+-[gamma-32P]ATP results in the autophosphorylation of a 50-kDa polypeptide (pp50) (Pauloin, A., Bernier, I., and Jollès, P. (1982) Nature 298, 574-576). We describe here a second protein kinase that is associated with calf brain and liver coated vesicles. This kinase, which phosphorylates casein and phosvitin but not histone and protamine using either ATP or GTP, co-fractionates with coated vesicles as assayed by gel filtration, electrophoresis, and sedimentation. The enzyme can be extracted with 0.5 M Tris-HCl or 1 M NaCl, and can be separated from the pp50 kinase as well as the other major coat proteins. We identified this enzyme as casein kinase II based on physical and catalytic properties and by comparative studies with casein kinase II isolated from brain cytosol. It has a Stokes radius of 4.5 nm, a catalytic moiety of approximately 45 kDa, and labels a polypeptide of 26 kDa when the pure enzyme is assayed for autophosphorylation. Its activity is inhibited by heparin and not affected by cAMP, phospholipids, or calmodulin. This protein kinase preferentially phosphorylates clathrin beta-light chain. The phosphorylation is markedly stimulated by polylysine and inhibited by heparin. Isolated beta-light chain as well as beta-light chain in triskelions or in intact coated vesicles is phosphorylated. All of the phosphate (0.86 mol of Pi/mol of clathrin beta-light chain) is incorporated into phosphoserine.