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U Pfeffer

Publications and source records attributed to U Pfeffer.

32 records · Page 2Linked to original sources
PubMed1992

Post-transcriptional control of H3 histone variants synthesis.

In cultured HeLa cells the rates of H3.1 and H3.2 synthesis measured by pulse labeling experiments reflect the steady state content of the two histone variants. This pattern, however, is largely modified when histone translation is carried out in vitro on RNA isolated from the same cell line. In vivo, H3.1 and H3.2 are synthesized approximately at the same rates while the product of H3 mRNA translation in vitro is mostly represented by H3.1 histones. Factors which have so far been invoked for the control of histone messenger RNA stability and translation efficiency are not sufficient to explain our data which in addition indicate that histone H3.1 and H3.2 have different roles in the organization of the genetic material.

Autoradiography↗
PubMed1991

Cell cycle dependent alterations of chromatin structure in situ as revealed by the accessibility of the nuclear protein AF-2 to monoclonal antibodies.

We have recently described a novel nuclear antigen, AF-2, which is related to cell cycle dependent alterations of chromatin structure. We show by two parameter flow cytometry on a cell by cell basis that the antigen is accessible to specific monoclonal antibodies only in mitotic and postmitotic early G1-phase cells. The evaluation of nuclease susceptibility and AF-2 antigen accessibility reveals different subcompartments of the G1-phase of the cell cycle with distinct chromatin conformations. Digestion with DNase I seems to alter the chromatin structure according to concentration and this is reflected by an increase of the antigen accessibility. Chromatin in the more condensed early G1-phase is specifically digested by lower concentrations of the enzyme than chromatin in later stages of interphase. Chromatin from cells in the late-G1, S-, and G2-phases shows a higher relative resistance to DNase I and a reduced accessibility of the AF-2 antigen to monoclonal antibodies. Nuclease S1 has a similar effect on chromatin topology, as revealed by the reaction with anti-AF-2 antibodies, without digestion of detectable amounts of DNA. The antigen becomes available to the antibodies in almost all cells by digestion with high concentrations of DNase I or Nuclease S1.

Antibodies, Monoclonal↗
PubMed1991

A novel protein related to cell cycle-dependent alterations of chromatin structure.

We have detected a novel nuclear antigen, AF-2, which appears to be involved in cell cycle-dependent alterations of chromatin structure. Specific monoclonal antibodies detect the antigen spread over the whole cell during mitosis and in islet-like structures in the nuclei of a subpopulation of cells in interphase. Upon nucleolytic digestion of fixed cells, the antigen becomes available to the antibodies in all cells, indicating that AF-2 antigen is present during the whole cell cycle but differentially accessible. Digestion with the single strand specific S1 nuclease reveals that the alteration of chromatin structure induced by the introduction of nicks into the DNA rather than the digestion of DNA bound to the immunogenic epitope accounts for the change in accessibility of AF-2 antigen in interphase nuclei. The epitope recognized by the antibody in human cells is present in two polypeptides of 65 and 36 kDa, respectively, which are tightly bound to chromatin and cross-linkable to the nuclear matrix. The proteins also occur in the midbody during cytokinesis. The immunogenic epitope is conserved between man and fission yeast.

Antibodies, Monoclonal↗
PubMed1989

Histone acetylation in conjugating Tetrahymena thermophila.

We have monitored histone acetylation during conjugation of the ciliated protozoan Tetrahymena thermophila using antibodies against the tetraacetylated form of H4 histone (Pfeffer, U., N. Ferrari, and G. Vidali. 1986. J. Biol. Chem. 261:2496-2498). During meiosis, the three prezygotic divisions, fertilization, and the first postzygotic division, micronuclei, do not contain highly acetylated forms of H4 histone. However, after the second postzygotic division, when anteriorly located micronuclei begin to develop into new macronuclei, they are strongly stained by the anti-tetraacetylated H4 histone antibody. In the old macronucleus, histones are actively deacetylated when it has ceased to transcribe but before it is eliminated. Histone acetylation processes analyzed here appear to be correlated to the commitment to transcription rather than to the transcription process itself. This is in good correlation with evidence we have obtained in chick erythrocyte nuclei during reactivation upon fusion with mammalian cells (Pfeffer, U., N. Ferrari, F. Tosetti, and G. Vidali. 1988. Exp. Cell Res. 178:25-30). Furthermore, it becomes clear from our data that histone acetylation occurs in close correlation to the position of nuclei within the cytoplasm of T. thermophila. Mechanisms that control differential histone acetylation and deacetylation are discussed.

Acetylation↗
PubMed1988

In vivo binding of retinol to chromatin. The binding is mediated by a lipoprotein.

We have previously shown that exposure of responding cells to vitamin A leads to profound modifications of chromatin structure as revealed by an increased susceptibility to DNase I digestion, modified patterns of histone acetylation, and impaired synthesis of a nonhistone chromosomal protein (Ferrari, N., and Vidali, G. (1985) Eur. J. Biochem. 151, 305-310). The present results show that these effects are most probably due to the direct interaction between retinol and chromatin, and analysis of mononucleosomes and higher oligomers obtained from retinol-treated cells shows that retinol is indeed tightly bound to chromatin. Enzymatic digestions of vitamin A containing nucleosomes with proteinase K, phospholipase C, and phospholipase A2 support a model where the final binding of retinol to chromatin is mediated by a lipoprotein: the recognition of the binding sites on DNA being dictated by the proteic component while the hydrophobic retinol is solubilized in the fatty acid moiety.

Cell Nucleus↗
PubMed1988

Histone acetylation: a step in gene activation.

Cellular ageing appears to consist mainly in a loss of adaptability and a progressive decrease in the capacity of the cell to maintain homeostasis. Such age related phenomenon can be the result of stochastic or of programmed events, and may occur through changes in the base pairs or coding of the DNA, through increasing levels of error in transcription and finally through alterations at the translation step of proteins synthesis. The purpose of this chapter is to present histone acetylation as a key event in the control of chromatin structure and transcription.

Acetylation↗
PubMed1988

Histone hyperacetylation is induced in chick erythrocyte nuclei during reactivation in heterokaryons.

Transcriptionally inactive avian red blood cell nuclei were reactivated by Sendai virus-induced fusion of chicken erythrocytes with HeLa cells. We have used antibodies which specifically recognize the tetraacetylated form of H4 histone to show that histone hyperacetylation is an event required for chromatin reorganization leading to a transcriptionally competent chromatin structure.

Acetylation↗
PubMed1987

Nucleosomal structure as probed by H3 histone thiol reactivity. Conformation of H3 histone variants is differently affected by thiol group reagents.

Two H3 histone variants are found in equal amount in HeLa cells, and they have been characterized by two-dimensional gel electrophoresis followed by reaction with specific antibodies. These molecules are the only cysteine-containing histones, and they have been used as the target for thiol-specific reagents, in intact nuclei, isolated nucleosomes, histone complexes, and purified histones. Cysteine residues are available to N-ethylmaleimide only when histones are disassembled from the core particles. Upon reaction with these reagents, one of the H3 variants undergoes profound conformational changes, as revealed by an altered electrophoretic mobility.

Acetylation↗
PubMed1986

Availability of hyperacetylated H4 histone in intact nucleosomes to specific antibodies.

Specific antibodies against the tetra-acetylated form of H4 histone have been elicited in the rabbit. They do not cross-react with the non-, mono-, and di-acetylated forms of the histone molecule but a slight cross-reactivity with the tri-acetylated form of H4 histone is observed. Our studies also show that hyperacetylated H4 histones are recognized by the antibodies in intact nucleosomes.

Acetylation↗
PubMedDate not supplied

Are there CAG repeat expansion-related disorders outside the central nervous system?

Expansions of poly-glutamine tracts in proteins that are expressed in the central nervous system cause neurodegenerative diseases. The altered proteins accumulate over long periods of time, forming nuclear inclusions, and lead to neuronal cell death. A similar mechanism could also be operant in non-dividing cells outside the central nervous system because nuclear inclusions are not limited to neurons. In addition, variations of the repeat length within the normal range may affect cellular function as it has been shown for the androgen receptor that is involved in neoplastic degeneration of several tissues. We have identified a poly-glutamine/poly-proline repeat in the homeobox gene DLX6. DLX genes are expressed in non-proliferative cells of the apical ectodermal ridge of developing limbs. Ablation of these cells leads to limb malformation. We propose that CAG triplet expansions in this gene could lead to cell death in the apical ectodermal ridge causing limb malformations. Indeed, autosomal dominant limb malformations with increasing severity in successive generations have been linked to the chromosomal region that contains DLX6. The analysis of a limited number of patients affected by split hand/foot malformation so far revealed only a slight modifier effect of repeat length within the normal range and no expansions have been detected.

Animals↗
PubMedDate not supplied

Antiangiogenic activity of chemopreventive drugs.

Tumors growing within the host form dynamic aberrant tissue that consists of host components, including the stroma, an expanding vasculature and often chronic inflammation, in addition to the tumor cells themselves. These host components can contribute to, rather than limit, tumor expansion, whereas deprivation of vessel formation has the potential to confine tumors in small, clinically silent foci. Therapeutic inhibition of vessel formation could be best suited to preventive strategies aimed at the suppression of angiogenesis in primary tumors in subjects at risk, or of micrometastases after surgical removal of a primary tumor. Our analysis of potential cancer chemopreventive molecules including N-acetylcysteine, green tea flavonoids and 4-hydroxyphenyl-retinamide has identified antiangiogenic activities that could account--at least in part--for the tumor prevention effects observed with these compounds. These drugs appear to target common mechanisms of tumor angiogenesis that may permit identification of critical targets for antiangiogenic therapy and antiangiogenic chemoprevention.

Acetylcysteine↗
PubMedDate not supplied

Occurrence of "stress"-proteins in yeast after heat-shock, acrylonitrile treatment and during the stationary growth phase.

The response of yeast cells to different kinds of "stress" is not identical. Cells of the stationary growth phase synthesize three new proteins of molecular weights 68, 27 and 24 kD, compared with cells of the exponential growth phase, while heat-shocked cells exhibit new proteins of 100, 90, 84, 70 and 24 kD. After treatment with acrylonitrile two new proteins with molecular weights of 70 and 46 kD appear. However, all three kinds of "stress" lead to the induction of a ribonuclease.

Acrylonitrile↗