Wyniki wyszukiwania - Biblioteka Nauki

1

Bacterial DNA repair genes and their eukaryotic homologues: 5. The role of recombination in DNA repair and genome stability

100%

Nowosielska A.

Acta Biochimica Polonica

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2007

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tom 54

|

nr 3

483-494

EN

Recombinational repair is a well conserved DNA repair mechanism present in all living organisms. Repair by homologous recombination is generally accurate as it uses undamaged homologous DNA molecule as a repair template. In Escherichia coli homologous recombination repairs both the double-strand breaks and single-strand gaps in DNA. DNA double-strand breaks (DSB) can be induced upon exposure to exogenous sources such as ionizing radiation or endogenous DNA-damaging agents including reactive oxygen species (ROS) as well as during natural biological processes like conjugation. However, the bulk of double strand breaks are formed during replication fork collapse encountering an unrepaired single strand gap in DNA. Under such circumstances DNA replication on the damaged template can be resumed only if supported by homologous recombination. This functional cooperation of homologous recombination with replication machinery enables successful completion of genome duplication and faithful transmission of genetic material to a daughter cell. In eukaryotes, homologous recombination is also involved in essential biological processes such as preservation of genome integrity, DNA damage checkpoint activation, DNA damage repair, DNA replication, mating type switching, transposition, immune system development and meiosis. When unregulated, recombination can lead to genome instability and carcinogenesis.

2

Essential role of the BRCA2B gene in somatic homologous recombination in Arabidopsis thaliana

100%

Amritha P. P. , Shah J. M.

BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology

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2023

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tom 104

|

nr 4

3

Current experimental strategies for investigating human hematopoietic stem cell biology

86%

Ratajczak M. Z. , Gewirtz A. M.

Folia Histochemica et Cytobiologica

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1996

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tom 34

|

nr 2

4

Chloroplast transformation reveals that tonbacco ycf5 is involved in photosynthesis

86%

Tsuruya K. , Suzuki M. , Plader W. , Sugita C. , Sugita M.

Acta Physiologiae Plantarum

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2006

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tom 28

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nr 4

EN

Hypothetical chloroplast reading frame 5 (ycf5) is encoded by the chloroplast genome and potentially specifies a protein of 313 amino acids in tobacco. A northern blot analysis showed that ycf5 transcripts accumulated at substantial levels in the chloroplasts, but not in the proplastids of nonphotosynthetic cultured cells. In an attempt to determine the function of ycf5, we constructed mutant alleles for the targeted deletion of ycf5. The mutant allele was introduced into the tobacco chloroplast genome by biolistic chloroplast transformation to replace the corresponding wild-typeycf5 alleles by homologous recombination. Homoplasmic ycf5-knockout tobacco plants displayed a pale-green phenotype. An analysis of the transient increase in chlorophyll fluorescence suggested that the electron flow around photosystem II (PSII) was completely impaired in the ycf5-deficient transformants. These findings indicate that ycf5 is indeed a functional gene, and that its gene product is involved in the generation of functional PSII units. This is the first report of the isolation and characterization of ycf5-knockout mutants in higher plants.

5

Non-homologous DNA end joining.

72%

Pastwa E. , Błasiak J.

Acta Biochimica Polonica

|

2003

|

tom 50

|

nr 4

891-908

EN

DNA double-strand breaks (DSBs) are a serious threat for the cell and when not repaired or misrepaired can result in mutations or chromosome rearrangements and eventually in cell death. Therefore, cells have evolved a number of pathways to deal with DSB including homologous recombination (HR), single-strand annealing (SSA) and non-homologous end joining (NHEJ). In mammals DSBs are primarily repaired by NHEJ and HR, while HR repair dominates in yeast, but this depends also on the phase of the cell cycle. NHEJ functions in all kinds of cells, from bacteria to man, and depends on the structure of DSB termini. In this process two DNA ends are joined directly, usually with no sequence homology, although in the case of same polarity of the single stranded overhangs in DSBs, regions of microhomology are utilized. The usage of microhomology is common in DNA end-joining of physiological DSBs, such as at the coding ends in V(D)J (variable(diversity) joining) recombination. The main components of the NHEJ system in eukaryotes are the catalytic subunit of DNA protein kinase (DNA-PKcs), which is recruited by DNA Ku protein, a heterodimer of Ku70 and Ku80, as well as XRCC4 protein and DNA ligase IV. A complex of Rad50/Mre11/Xrs2, a family of Sir proteins and probably other yet unidentified proteins can be also involved in this process. NHEJ and HR may play overlapping roles in the repair of DSBs produced in the S phase of the cell cycle or at replication forks. Aside from DNA repair, NHEJ may play a role in many different processes, including the maintenance of telomeres and integration of HIV-1 genome into a host genome, as well as the insertion of pseudogenes and repetitive sequences into the genome of mammalian cells. Inhibition of NHEJ can be exploited in cancer therapy in radio-sensitizing cancer cells. Identification of all key players and fundamental mechanisms underlying NHEJ still requires further research.

6

RNA recombination in brome mosaic virus, a model plus strand RNA virus

72%

Figlerowicz M. , Bujarski J. J.

Acta Biochimica Polonica

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1998

|

tom 45

|

nr 4

EN

Studies on the molecular mechanism of genetic recombination in RNA viruses have progressed at the time when experimental systems of efficient recombination crossovers were established. The system of brome mosaic virus (BMV) represents one of the most useful and most advanced tools for investigation of the molecular aspects of the mechanism of RNA-RNA recombination events. By using engineered BMV RNA components, the occurrence of both homologous and nonhomologous crosses were demonstrated among the segments of the BMV RNA genome. Studies show that the two types of crossovers require different RNA signal sequences and that both types depend upon the participation of BMV replicase proteins. Mutations in the two BMV-encoded replicase polypeptides (proteins 1a and 2a) reveal that their different regions participate in homologous and in nonhomologous crossovers. Based on all these data, it is most likely that homologous and nonhomologous recombinant crosses do occur via two different types of template switching events (copy-choice mechanism) where viral replicase complex changes RNA templates during viral RNA replication at distinct signal sequences. In this review we discuss various aspects of the mechanism of RNA recombination in BMV and we emphasize future projections of this research.

7

Non-homologous DNA end joining

58%

Pastwa E. , Blasiak J.

Acta Biochimica Polonica

|

2003

|

tom 50

|

nr 4

EN

DNA double-strand breaks (DSBs) are a serious threat for the cell and when not repaired or misrepaired can result in mutations or chromosome rearrangements and eventually in cell death. Therefore, cells have evolved a number of pathways to deal with DSB including homologous recombination (HR), single-strand annealing (SSA) and non-homologous end joining (NHEJ). In mammals DSBs are primarily repaired by NHEJ and HR, while HR repair dominates in yeast, but this depends also on the phase of the cell cycle. NHEJ functions in all kinds of cells, from bacteria to man, and depends on the structure of DSB termini. In this process two DNA ends are joined directly, usually with no sequence homology, although in the case of same polarity of the single stranded overhangs in DSBs, regions of microhomology are utilized. The usage of microhomology is common in DNA end-joining of physiological DSBs, such as at the coding ends in V(D)J (variable(diversity) joining) recombination. The main components of the NHEJ system in eukaryotes are the catalytic subunit of DNA protein kinase (DNA-PKcs), which is recruited by DNA Ku protein, a heterodimer of Ku70 and Ku80, as well as XRCC4 protein and DNA ligase IV. A complex of Rad50/Mre11/Xrs2, a family of Sir proteins and probably other yet unidentified proteins can be also involved in this process. NHEJ and HR may play overlapping roles in the repair of DSBs produced in the S phase of the cell cycle or at replication forks. Aside from DNA repair, NHEJ may play a role in many different processes, including the maintenance of telomeres and integration of HIV-1 genome into a host genome, as well as the insertion of pseudogenes and repetitive sequences into the genome of mammalian cells. Inhibition of NHEJ can be exploited in cancer therapy in radio- sensitizing cancer cells. Identification of all key players and fundamental mechanisms underlying NHEJ still requires further research.