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V Jackson

Publications and source records attributed to V Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1981

The sites of deposition of newly synthesized histone.

The chromosomal fragments produced by nuclease digestion of freshly replicated chromatin migrate more rapidly relative to bulk chromatin when analyzed in nucleoprotein gels. The cause of the anomalous migration has been studied and the evidence indicates that rather than reflecting a shorter nucleosomal repeat in vivo that it may be a consequence of nucleosome sliding during the digestion itself. The distinct electrophoretic characteristics of nucleosomal material containing newly replicated DNA have enabled us to examine their histone composition by two dimensional electrophoresis. We find that nucleosomes containing new DNA also contain newly synthesized histones H3 and H4. In contrast more than 50% of newly synthesized H2A and H2B, and essentially all of new H1, are deposited at sites on the bulk chromatin distinct from that material containing newly replicated DNA. In addition we show that newly synthesized histones H3 and H4 are bound unusually weakly when they first become associated with the chromatin.

Animals↗
PubMed1981

A reevaluation of new histone deposition on replicating chromatin.

In this study, we have density-labeled newly replicated DNA in hepatoma tissue culture cells and separated the newly replicated nucleoprotein from bulk material using density gradient centrifugation. These experiments indicate that only newly synthesized histones H3 and H4 deposit specifically on newly replicated DNA. Histones H2A and H2B show a partial preference and histone H1 shows no preference for deposition on new DNA. These experiments also indicate that for a whole cell cycle, the non-H1 histones remain associated with the same DNA upon which they were initially deposited. However, when that region is replicated during the next cell cycle, the histones distribute equally to both daughter strands. An increase or decrease in the level of histone modification (acetylation) induced by sodium butyrate treatment does not alter the in vivo stability of the histone-DNA interactions. Experiments which involved labeling SV40 minichromosomes with [3H]lysine confirm our observations that only newly synthesized histone H3 and H4 are selectively depend on replicated DNA.

Animals↗
PubMed1981

A new method for the isolation of replicative chromatin: selective deposition of histone on both new and old DNA.

We have developed a new method for isolating subcellular components after fixation of whole cells with formaldehyde. By a number of criteria we establish that the fixation does not alter or cause rearrangement of nucleosomal structure of either newly replicated or old chromatin. Using this approach we can almost completely resolve newly replicated chromatin from preexisting material on the basis of the difference in density. Newly replicated chromatin (even from cycloheximide-treated cells) appears to contain nucleosomes on both daughter strands. Exploiting the ability to separate newly synthesized chromatin, we have reexamined the question of the deposition of new histone at the replication fork. We find that newly synthesized histones H3 and H4 are deposited onto new DNA and stay in place for a significant time. In contrast new H1 is deposited on old DNA and new H2A-H2B, while they may be transiently bound to new DNA, are largely associated with preexisting chromatin.

Animals↗
PubMed1981

Use of whole-cell fixation to visualize replicating and maturing simian virus 40: identification of new viral gene product.

Formaldehyde fixation of simian virus 40 (SV40)-infected CV-1 cells at appropriate times after infection permits us to isolate crosslinked complexes of SV40 minichromosomes during the time of DNA replication and during packaging with viral proteins. Such crosslinked complexes can be separated on the basis of density on CsCl/guanidine . HCl density gradients. During the course of these studies we observed the presence of a low molecular weight protein in a region of the gradient much enriched with viral nucleoproteins. This protein is present only in infected cells and has a molecular weight and amino acid composition consistent with it being the product of the so-called SV40 agnogene.

Amino Acid Sequence↗
PubMed1979

Comparative studies on highly metabolically active histone acetylation.

Histone acetate is hydrolyzed rapidly in logarithmically dividing hepatoma tissue culture cells (Jackson, V., Shires, A., Chalkley, R. and Granner, D.K. (1975) J. Biol. Chem. 250, 4856--4863). The phenomenon has been analyzed further in hepatoma tissue culture cells at various stages of the cell cycle, in stationary phase, and in the presence of actinomycin D. We also investigated the phenomenon in Tetrahymena pyriformis macronuclei, bovine thymocytes, and human foreskin fibroblasts. The data suggest that this highly metabolically active histone acetylation while altered in mitotic cells, is independent of the overall rate of cell division, and is only slightly sensitive to actinomycin D. Finally, we conclude that the same general phenomenon is found in both cancerous and normal cells and is apparently common to cells from various stages of the evolutionary scale.

Acetylation↗
PubMed1978

Falciparum malaria in seamen.

Three cases of Plasmodium falciparum malaria in seamen, all acquired while working off tropical West Africa, and all in patients coming in for treatment at a New Orleans hospital during one six-week period, are described in the context of the importance of considering recent travel history for arrival at the correct diagnosis and treatment. Two of the three patients whose cases are reported had taken some form of malarial chemoprophylaxis during their voyage.

Adult↗
PubMed1978

Studies on histone organization in the nucleosome using formaldehyde as a reversible cross-linking agent.

A new procedure is described which allows selective reversal of formaldehyde cross-linking in both histone-histone and histone-DNA of nuclei isolated from calf thymus. All ten possible dimers of the four non-H1 histones, H3, H2B, H2A and H4, are observed, the major dimers being H3-H3, H3-H2A, H2B-H2A, H2a-H2A and two separate dimers of H2B-H4. Although oligomers of the non-H1 histones are formed by prolonged treatment with this reagent, 50% of the histones continue to remain resistant to cross-linking with each other. For those histones which cross-linking with each other. For those histones which cross-link, the site of cross-linking within the molecules is located in the "core" (trysin-resistant) regionand therfore indicates proximities for these molecules within the nucleosome. The core region also cross-links to DNA, indicating intimate interactions between this region in all the non-H1 histones with DNA.

Binding Sites↗
PubMed1977

Is dopamine a neurohormone of the adrenal medulla? Studies with morphine stimulation.

Dopamine (da) concentrations in rat adrenals, plasma and brain were variably elevated 1 h after a large parenteral dose of morphine. In adrenals, unlabelled DA increased 2-fold and labelled DA, synthesized from 3H-tyrosine, increased more than 4-fold. The increases could be prevented by inhibition of DA-synthesizing enzymes and spinal cord transection, respectively. Labelled DA in plasma increased 2.7-fold after morphine in intact rats but did not increase in those with spinal cord transection. It is concluded that: (1) morphine stimulates the adrenal by increasing nerve impulse flow, (2) increased nerve impulse flow increases DA synthesis and levels, and (3) the increased DA levels result in increased release of DA into the bloodstream.

Adrenal Medulla↗
PubMed1976

Deposition of histone onto the replicating chromosome: newly synthesized histone is not found near the replication fork.

We have studied the site of deposition of newly synthesized histone. It appears to be randomly distributed over the chromosomal material and does not become associated specifically with immediately post-replicational DNA, nor is it deposited in discrete continuous regions distal to the sites of DNA synthesis. The newly synthesized DNA, however, rapidly acquires a complement of chromosomal proteins; presumably, preexisting histones must migrate to become associated with post-replicational DNA.

Cells, Cultured↗
PubMed1975

Studies on highly metabolically active acetylation and phosphorylation of histones.

The capacity to effectively label tumor cell hostones using very short pulses of [3-H]acetate and [32-P]phosphate (1 to 10 min) has been developed. Four histone fractions F3, F2a1, F2a2, and F2b are extensively acetylated in short time periods. About 70% of the acetate accumulated on the histone during a short pulse is removed with a half-life of similar to 3 min. The rest of the metabolically active acetate is removed with a half-life of 30 to 40 min. Histones F2a1, F2a2, and F1 are acetylated at the NH2 terminus and this modification is metabolically stable. In short pulses, histones are labeled with 32-P in the order F2a2 greater than F1 greater than F3 greater than F2a1 greater than F2b. All fractions have a fairly rapid turnover time (t1/2 similar 20 to 40 min) except F1 phosphate which turns over some 5 times more slowly.

Acetates↗
PubMed1975

Phosphorylation of the lysine-rich histones throughout the cell cycle.

The phosphorylating of the lysine-rich histone at various stages in the cell cycle has been studied. In rapidly dividing cell populations the lysine-rich histone is phosphorylated rapidly after synthesis and more slowly once bound to the chromosome. The half-life of hydrolysis of such interphase phosphorylation in 5 hr except during mitosis when the phosphata hydrolysis increases almost three-fold. During mitosis there is extensive phosphorylation at sites different from those phosphorylated during interphase and a smaller measure of sites common to both mitotic and interphase cells. The sites of mitotic phosphorylation are most critically distinguished from those phosphorylated in interphase by the rapidly hydrolysis of M-phase phosphohistone when the cells divide and enter the G1 phase of the cell cycle.

Autoradiography↗
PubMed1975

The phosphorylation region of lysine-rich histone in dividing cells.

N-Bromosuccinimide cleavage of in vivo 32P-labelled lysine-rich histone isolated from rapidly dividing cells has been studied. N-Bromosuccinimide cleaves F1-histone into two fragments, a small N-terminal piece and a larger C-terminal portion. The phosphate-induced microheterogeneity and associated radioactivity which has been linked to cell replication, is found in the carboxyterminal fragment, No phosphorous is found associated with the amino-terminal fragment when histone phosphorylation is associated with cell division. The specific tryptic phosphopeptides obtained from in vivo labelled F1 are clearly different from those obtained from in vitro incubations of free F1-histones and cytoplasmic protein kinase.

Animals↗
PubMed1975

Deposition of histones onto replicating chromosomes.

The mode of distribution of newly synthesized and pre-existing histones has been studied during the process of chromosome replication. Newly synthesized histone was labeled with [3H]lysine and newly synthesized DNA was density labeled with iododeoxyuridine. The histone was covalently linked to DNA, and radiolabeled histone was analyzed on CsCl density gradients. We have defined conditions that do not give rise to histone randomization during isolation, and also developed a method of defining the distribution of histones in chromatin on a density gradient in the unavoidable presence of nonhistone protein. Three possible modes of distribution of histone onto the replicating chromosome can be conceived; we describe experiments designed to distinguish unequivocally among these possibilities and conclude that histones are deposited randomly onto the chromosome.

Carcinoma, Hepatocellular↗