Wyniki wyszukiwania - Biblioteka Nauki

1

Impaired base excision repair is related to the pathogenesis of non-alcoholic fatty liver disease

100%

Ziółkowska S. , Czarny P. , Szemraj J.

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tom 16

5-11

EN

Non-alcoholic fatty disease (NAFLD) is a liver disorder that affects up to 30% of the population, mainly in Western countries. It is estimated that up to 75% of NAFLD patients will develop a more aggressive form of the disease, non-alcoholic steatohepatitis (NASH). NAFLD can lead to fibrosis and liver failure; however, it is difficult to diagnose NAFLD due to its non-specific symptoms. Unfortunately, there is no treatment available for this disease. The risk factors of NAFLD are obesity and insulin resistance (IR). The molecular factors that seem to play an important role in the pathogenesis of NAFLD are oxidative stress as well as impaired DNA damage repair processes; a great body of evidence confirms an association with the base excision repair (BER) pathway. The activity of BER is decreased in patients with NAFLD and in animal models of this disease. In order to better understand the underlying basis of the disease, knowledge should be broadened in the area of DNA repair in NAFLD.

2

Poly(ADP-ribose) polymerase in base excision repair: always engaged, but not essential for DNA damage processing.

75%

Allinson S. L. , Dianova I. I. , Dianov G. L.

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tom 50

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nr 1

169-179

EN

Poly(ADP-ribose) polymerase (PARP-1) is an abundant nuclear protein with a high affinity for single- and double-strand DNA breaks. Its binding to strand breaks promotes catalysis of the covalent modification of nuclear proteins with poly(ADP-ribose) synthesised from NAD+. PARP-1-knockout cells are extremely sensitive to alkylating agents, suggesting the involvement of PARP-1 in base excision repair; however, its role remains unclear. We investigated the dependence of base excision repair pathways on PARP-1 and NAD+ using whole cell extracts derived from normal and PARP-1 deficient mouse cells and DNA substrates containing abasic sites. In normal extracts the rate of repair was highly dependent on NAD+. We found that in the absence of NAD+ repair was slowed down 4-6-fold after incision of the abasic site. We also established that in extracts from PARP-1 deficient mouse cells, repair of both regular and reduced abasic sites was increased with respect to normal extracts and was NAD+-independent, suggesting that in both short- and long-patch BER PARP-1 slows down, rather than stimulates, the repair reaction. Our data support the proposal that PARP-1 does not play a major role in catalysis of DNA damage processing via either base excision repair pathway.

3

Poly[ADP-ribose] polymerase in base excision repair: always engaged, but not essential for DNA damage processing

75%

Allinson S. L. , Dianova I. I. , Dianov G. L.

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nr 1

EN

Poly(ADP-ribose) polymerase (PARP-1) is an abundant nuclear protein with a high affinity for single- and double-strand DNA breaks. Its binding to strand breaks promotes catalysis of the covalent modification of nuclear proteins with poly(ADP-ribose) synthesised from NAD+ . PARP-1-knockout cells are extremely sensitive to alkylating agents, suggesting the involvement of PARP-1 in base excision repair; however, its role remains unclear. We investigated the dependence of base excision repair pathways on PARP-1 and NAD+ using whole cell extracts derived from normal and PARP-1 deficient mouse cells and DNA substrates containing abasic sites. In normal extracts the rate of repair was highly dependent on NAD+ . We found that in the absence of NAD+ repair was slowed down 4-6-fold after incision of the abasic site. We also established that in extracts from PARP-1 deficient mouse cells, repair of both regular and reduced abasic sites was increased with respect to normal extracts and was NAD+ -independent, suggesting that in both short- and long-patch BER PARP-1 slows down, rather than stimulates, the repair reaction. Our data support the proposal that PARP-1 does not play a major role in catalysis of DNA damage processing via either base excision repair pathway.

4

Bacterial DNA repair genes and their aukaryotic homologues: 1. Mutations in genes involved in base excision repair [BER] and DNA-end processors and their implication in mutagenesis and human disease

51%

Krwawicz J. , Arczewska K. D. , Speina E. , Maciejewska A. , Grzesiuk E.

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tom 54

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nr 3

EN

Base excision repair (BER) pathway executed by a complex network of proteins is the major system responsible for the removal of damaged DNA bases and repair of DNA single strand breaks (SSBs) generated by environmental agents, such as certain cancer therapies, or arising spontaneously during cellular metabolism. Both modified DNA bases and SSBs with ends other than 3'-OH and 5'-P are repaired either by replacement of a single or of more nucleotides in the processes called short-patch BER (SP-BER) or long-patch BER (LP-BER), respectively. In contrast to Escherichia coli cells, in human ones, the two BER sub-pathways are operated by different sets of proteins. In this review the selection between SP- and LP-BER and mutations in BER and end-processors genes and their contribution to bacterial mutagenesis and human diseases are considered.

5

Oxidative damage to DNA and antioxidant status in aging and age-related diseases

51%

Olinski R. , Siomek A. , Rozalski R. , Gackowski D. , Foksinski M. , Guz J. , Dziaman T. , Szpila A. , Tudek B.

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tom 54

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nr 1

EN

Aging is a complex process involving morphologic and biochemical changes in single cells and in the whole organism. One of the most popular explanations of how aging occurs at the molecular level is the oxidative stress hypothesis. Oxidative stress leads in many cases to an age-dependent increase in the cellular level of oxidatively modified macromolecules including DNA, and it is this increase which has been linked to various pathological conditions, such as aging, carcinogenesis, neurodegenerative and cardiovascular diseases. It is, however, possible that a number of short-comings associated with gaps in our knowledge may be responsible for the failure to produce definite results when applied to understanding the role of DNA damage in aging and age-related diseases.

6

Mismatch dependent uracil-thymine-DNA glycosylases excise exocyclic hydroxyethano and hydroxypropano cytosine adducts

44%

Borys-Brzywczy E. , Arczewska K. D. , Saparbaev M. , Hardeland U. , Schar P. , Kusmierek J. T.

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nr 1

EN

Exocyclic adducts of DNA bases, such as etheno- and hydroxyalkano- ones, are generated by a variety of bifunctional agents, including endogenously formed products of lipid peroxidation. In this work we selectively modified cytosines in the 5’-d(TTT TTT CTT TTT CTT TTT CTT TTT T)-3’ oligonucleotide using: chloroacetaldehyde to obtain 3,N4-α-hydroxyethano- (HEC) and 3,N4-etheno- (epsilonC), acrolein to obtain 3,N4-α-hydroxypropano- (HPC) and crotonaldehyde to obtain 3,N4αhydroxy-γ-methylpropano- (mHPC) adducts of cytosine. The studied adducts are alkali-labile which results in oligonucleotide strain breaks at the sites of modification upon strong base treatment. The oligonucleotides carrying adducted cytosines were studied as substrates of Escherichia coli Mug, human TDG and fission yeast Thp1p glycosylases. All the adducts studied are excised by bacterial Mug although with various efficiency: εC > HEC > HPC > mHPC. The yeast enzyme excises efficiently εC≥HEC>HPC, whereas the human enzyme excises only εC. The pH-dependence curves of excision of εC, HEC and HPC by Mug are bell shaped and the most efficient excision of adducts occurs within the pH range of 8.6–9.6. The observed increase of excision of HEC and HPC above pH 7.2 can be explained by deprotonation of these adducts, which are high pKa compounds and exist in a protonated form at neutrality. On the other hand, since εC is in a neutral form in the pH range studied, we postulate an involvement of an additional catalytic factor. We hypothesize that the enzyme structure undergoes a pH-induced rearrangement allowing the participation of Lys68 of Mug in catalysis via a hydrogen bond interaction of its ε-amino group with N4 of the cytosine exocyclic adducts.