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31.
32.
2-Deoxyribonolactone (3) is produced in DNA as a result of reaction with a variety of DNA damaging agents. The lesion undergoes beta-elimination to form a second metastable electrophilic product (4). In this study, DNA containing 2-deoxyribonolactone (3) and its beta-elimination product (4) are generated at specific sites using a photolabile nucleotide precursor. 2-Deoxyribonolactone is not incised by any of the 8 AP lyases tested. One enzyme, Escherichia coli endonuclease III, cross-links to 3, and the lesion strongly inhibits excision of typical abasic sites by this enzyme. Two of the enzymes, FPG and NEIL1 known to cleave normal abasic sites (1) by effecting beta,delta-elimination form cross-links to the butenolide lesion (4). The observed results are ascribable to characteristics of the enzymes and the lesions. These enzymes are also important for the removal of oxidative base lesions. These results suggest that high concentrations of 3 and 4 may exert significant effects on the repair of normal AP site and oxidative base lesions in cells by reducing the cellular activity of these BER enzymes either via cross-linking or competing with binding to the BER enzymes. 相似文献
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A parsimony analysis was performed on restriction sites at the Hba-ps4
pseudogene locus within one of four inversions associated with mouse t
haplotypes. The results suggest that all t haplotypes form a monophyletic
group and that the in (17)4 inversion originated before the radiation of
the Mus musculus species complex but after the divergence of the lineages
leading to M. spretus, M. abbotti, and M. hortulanus. A time frame based on
the evolutionary rate of mouse pseudogenes places the origin of this t
haplotype inversion at 1.5 Mya, or approximately 1.5 Myr after the origin
of the more proximal t complex inversion, in (17)2. The accumulated
evidence indicates that complete t haplotypes have been assembled in a
stepwise manner, with each of these inversions occurring on separate
chromosomal lineages and at different evolutionary times. In addition, the
evolutionary relationships of pseudogene sequences resulting from genetic
exchange between wild-type and t haplotype alleles were examined. Analysis
of sequences from the 5' and 3' sides of a putative site of recombination
resulted in cladograms with different topologies. The implications for
hypotheses concerning the evolutionary forces acting on t haplotypes and
their rapid propagation throughout worldwide populations of mice are
discussed.
相似文献
36.
Using oligonucleotide synthesis, we demonstrate a rapid and efficient method for the construction of DNA duplexes containing defined DNA lesions at specific positions. These DNA lesions include apyrimidinic sites, reduced apyrimidinic sites, and base-damage analogues consisting of O-methyl- or O-benzylhydroxylamine-modified apyrimidinic sites. A 49 base pair DNA duplex containing these lesions was specifically incised by the UvrABC nuclease complex. The incision sites occurred predominantly at the eighth phosphodiester bond 5' and the fifth phosphodiester bond 3' to the lesion. Multiple incisions were observed 3' to the lesion. The extent of DNA incisions was base-damage analogues greater than reduced apyrimidinic sites greater than apyrimidinic sites. Introduction of 3' or 5' nicks at the site of a base-damage analogue by treatment of these substrates with either endonuclease III or endonuclease IV reduced, but did not abolish, subsequent incision by the UvrABC complex, whereas introduction of a 3' nick at an abasic site increased the incision efficiency of the UvrABC complex. These data demonstrate a convergence of base and nucleotide excision repair pathways in the removal of specific base damages. 相似文献
37.
We have shown previously that endonuclease III from Escherichia coli, its yeast homolog Ntg1p and E. coli endonuclease VIII recognize single dihydrouracil (DHU) lesions efficiently. However, these enzymes have limited capacities for completely removing DHU, when the lesion is present on duplex DNA as a tandem lesion. A duplex 30-mer (duplex1920) containing tandem DHU lesions at positions 19 and 20 from the 5' terminus was used as a substrate for human endonuclease III (hNTH) and endonuclease VIII (NEIL1). Two cleavage products, 18beta and 19beta were formed, when duplex1920 was treated with hNTH. The 18beta corresponded to the expected beta-elimination product generated from duplex1920, when the 5'-DHU of the tandem DHU was processed by hNTH. Similarly, 19beta is the beta-elimination product generated, when the 3'-DHU of the tandem DHU was processed by hNTH; 19beta thus still contained a DHU lesion at the 3' terminus. When these hNTH reaction products were further treated with human APE1, a single new product that corresponded to an 18mer was observed. These data suggested that human APE1 can help to process the 3' terminals following the action of hNTH on DHU lesions. Similarly, when duplex1920 was treated with NEIL1, two cleavage products, 18p and 19p were observed. The 18p and 19p corresponded to the expected beta,delta-elimination products derived from NEIL1 induced cleavage at the 5'-DHU and 3'-DHU of the tandem DHU, respectively. The 3'-phosphoryl group present in 18p can be readily removed by T4 polynucleotide kinase (PNK) to yield an 18mer that is suitable for repair synthesis. However, 19p required the participation of both PNK and APE1 to generate the 18mer. Together, we suggest that the processing of DNA-containing tandem DHU lesions, initiated by hNTH and NEIL1 can be channeled into two sub-pathways, the PNK-independent, APE1-dependent and the PNK, APE1-dependent pathways, respectively. 相似文献
38.
Claribel Cruz-García Alison E Murray Jorge LM Rodrigues Jeffrey A Gralnick Lee Ann McCue Margaret F Romine Frank E Löffler James M Tiedje 《BMC microbiology》2011,11(1):64
Background
EtrA in Shewanella oneidensis MR-1, a model organism for study of adaptation to varied redox niches, shares 73.6% and 50.8% amino acid sequence identity with the oxygen-sensing regulators Fnr in E. coli and Anr in Pseudomonas aeruginosa, respectively; however, its regulatory role of anaerobic metabolism in Shewanella spp. is complex and not well understood. 相似文献39.
Carlos G PinheiroJr Eduardo LM Naves Pierre Pino Etienne Losson Adriano O Andrade Guy Bourhis 《Biomedical engineering online》2011,10(1):31
We have now sufficient evidence that using electrical biosignals in the field of Alternative and Augmented Communication is
feasible. Additionally, they are particularly suitable in the case of people with severe motor impairment, e.g. people with
high-level spinal cord injury or with locked-up syndrome. Developing solutions for them implies that we find ways to use sensors
that fit the user's needs and limitations, which in turn impacts the specifications of the system translating the user's intentions
into commands. After devising solutions for a given user or profile, the system should be evaluated with an appropriate method,
allowing a comparison with other solutions. This paper submits a review of the way three bioelectrical signals - electromyographic,
electrooculographic and electroencephalographic - have been utilised in alternative communication with patients suffering
severe motor restrictions. It also offers a comparative study of the various methods applied to measure the performance of
AAC systems. 相似文献