Wyniki wyszukiwania - Biblioteka Nauki

1

Size-dependent properties of nanostructured metal particles

100%

Schmid G.

Bulletin of the Polish Academy of Sciences. Chemistry

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1998

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tom Vol. 46, No. 3

229-235

EN

Ligand stabilized transition metal clusters exhibit size-dependent electronic behaviour. From the current-voltage characteristics of a 17 nm Pd cluster it can be followed that it behaves bulk-like at room temperature, but shows a Coulomb blockade at 4.2 K. Contrary to that, 1.4 nm Au clusters show a Coulomb blockade already at room temperature and a series of single electron transitions at 90 K. Quantum size behaviour of a series of Pd clusters is also demostrated by specific heat and susceptibility measurements. Activation energies for electron transitions between three-dimensionally organized 1.4 nm gold clusters, separated by spacer molecules of varying lengths, have been determined. Nanoporous alumina membranes serve as matrices to generate cluster wires which will be used to study electron transitions between clusters in one dimension.

2

The subcellular distribution of the p53 tumour suppressor, and organismal ageing

63%

Wesierska-Gadek J. , Schmid G.

Cellular and Molecular Biology Letters

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2005

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tom 10

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nr 3

3

Poly[ADP-ribose] polymerase-1 regulates the stability of the wild-type p53 protein

63%

Wesierska-Gadek J. , Schmid G.

Cellular and Molecular Biology Letters

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2001

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tom 06

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nr 2

4

Physiological ageing: role of p53 and PARP-1 tumor suppressors in the regulation of terminal senescence

51%

Wesierska-Gadek J. , Ranftler C. , Schmid G.

Journal of Physiology and Pharmacology. Supplement

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2005

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tom 56

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nr 2

77-88

EN

Ageing of organisms is among the most complex processes currently known. Understanding the molecular mechanism of physiological ageing is one of the most essential issues in biology and medicine because it is not possible to predict when and how a certain individual will start ageing. In the past centuries human life expectancies increased. Extension of life span is associated with increased susceptibility to a number of chronic diseases. Insight into the cellular and molecular targets of the ageing process would offer the opportunity to prevent at least some of the destructive processes. In the present paper the involvement of two tumor suppressor proteins: wild-type p53 and poly(ADP-ribose)polymerase-1 (PARP-1) in the regulation of cellular senescence and physiological ageing was reviewed. Moreover, the interaction and cross-talk between p53 and PARP1-1 was discussed.

5

Role of P53 tumor suppressor in ageing: regulation of transient cell cycle arrest and terminal senescence

51%

Wegierska-Gadek J. , Wojciechowski J. , Ranftler C. , Schmid G.

Journal of Physiology and Pharmacology

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2005

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tom 56

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nr 1

EN

In this study we investigated the function of p53 as a regulator of cell cycle progression in cycling and senescent cells. Using the conditional temperature-sensitive (ts) mutant we could prevent the detrimental effect of constitutive expression of high levels of wt p53 protein. High levels of wt p53 inhibited cell proliferation by blocking the cells to progress from G1 to S phase of the cell cycle. Flow cytometric analysis revelaed a maintenance of G1 cell population for a longer time depending on the prolonged expression of wt p53 protein. The p53 mediated inhibition of cell proliferation and of the cycle was reversible. However, a spontaneous increase of wt p53 occurring in ageing normal human MRC-5 fibroblasts was associated with irreversible reduction of proliferative potential. The accumulation of G1 cells was detected by flow cytometry. By the measurement of DNA content it is not possible to discriminate between cells arrested in G1 and Go phase, therefore, the expression of G1 markers was determined. Analysis of the expression of distinct cell cycle regulators revealed that quiescent MRC-5 cells were in Go phase. Our results indicate that cell cycle arrest occurring in senescent cells is associated with the Go transition.

6

Advantage of a baculovirus expression system for protein-protein interaction studies. Involvement of posttranslational phosphorylation in the interaction between wt p53 protein and poly[ADP-ribose] polymerase-1

51%

Schmid G. , Wojciechowski J. , Wesierska-Gadek J.

Acta Biochimica Polonica

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2005

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tom 52

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nr 3

EN

We recently observed an interaction between poly(ADP-ribose) polymerase-1 (PARP-1) and the tumor suppressor p53 protein. However, more extensive studies on both proteins, especially those on characterization of their domains involved in the interaction were difficult due to very low expression levels of p53 in mammalian cells. Therefore, we generated recombinant proteins for such studies. To clarify which domains of human PARP-1 and of human wild-type (wt) p53 were involved in this protein-protein interaction, we generated baculoviral constructs encoding full length or distinct functional domains of both proteins. Full length PARP-1 was simultaneously coexpressed in insect cells with full length wt p53 protein or its distinct truncated fragments and vice versa. Reciprocal immunoprecipitation of Sf9 cell lysates revealed that the central and carboxy-terminal fragments of p53 each were sufficient to confer binding to PARP-1, whereas the amino-terminal part harbouring the transactivation functional domain was dispensable. On the other hand, the amino-terminal and central fragments of PARP-1 were both necessary for complex formation with p53 protein. Since the most important features of p53 protein are regulated by phosphorylation, we addressed the question whether its phosphorylation is essential for the binding between the two proteins. Baculovirally expressed wt p53 was post-translationally modified. At least six distinct p53 isomers were resolved by immunoblotting following two-dimensional separation of baculovirally expressed wt p53 protein. Using specific phospho-serine antibodies, we identified phosphorylation of baculovirally expressed p53 protein at five distinct sites. To define the role of p53 phosphorylation, pull-down assays using untreated and dephosphorylated p53 protein were performed. Dephosphorylated p53 failed to bind PARP-1, indicating that complex formation between the two proteins was regulated by phosphorylation of p53. The marked phosphorylation of p53 at Ser392 observed in unstressed cells suggests that the phosphorylated carboxy-terminal part of p53 undergoes complex formation with PARP-1 resulting in masking of the NES and thereby preventing its export.