771 research outputs found
Nucleotide excision repair II: From yeast to mammals
An intricate network of repair systems safeguards the integrity of genetic material, by eliminating DNA lesions induced by numerous environmental and endogenous genotoxic agents. Nucleotide excision repair (NER) is one of the most versatile DNA repair systems. Deficiencies in this process give rise to the classical human DNA repair disorders xeroderma pigmentosum (XP) and Cockayne's syndrome (CS), and to a recently recognized disease called PIBIDS, a photosensitive form of the brittle hair disorder trichothiodystrophy. This is the second of a two-part review on NER. Part I (in the previous issue of TIG) concentrated on the main characteristics of the NER pathway of E. coli and yeast. Part II compares the mammalian and yeast systems, and attempts to integrate current knowledge on the eukaryotic pathway to suggest an outline for the reaction mechanism
Phase diagram of orbital-selective Mott transitions at finite temperatures
Mott transitions in the two-orbital Hubbard model with different bandwidths
are investigated at finite temperatures. By means of the self-energy functional
approach, we discuss the stability of the intermediate phase with one orbital
localized and the other itinerant, which is caused by the orbital-selective
Mott transition (OSMT). It is shown that the OSMT realizes two different
coexistence regions at finite temperatures in accordance with the recent
results of Liebsch. We further find that the particularly interesting behavior
emerges around the special condition and J=0, which includes a new type
of the coexistence region with three distinct states. By systematically
changing the Hund coupling, we establish the global phase diagram to elucidate
the key role played by the Hund coupling on the Mott transitions.Comment: 4 pages, 6 figure
On General Axial Gauges for QCD
General Axial Gauges within a perturbative approach to QCD are plagued by
'spurious' propagator singularities. Their regularisation has to face major
conceptual and technical problems. We show that this obstacle is naturally
absent within a Wilsonian or 'Exact' Renormalisation Group approach and explain
why this is so. The axial gauge turns out to be a fixed point under the flow,
and the universal 1-loop running of the gauge coupling is computed.Comment: 4 pages, latex, talk presented by DFL at QCD'98, Montpellier, July
2-8, 1998; to be published in Nucl. Phys. B (Proc. Suppl.
Nucleotide excision repair I: from E.coli to yeast.
Genetic information is constantly deteriorating, mainly as a consequence of the action of numerous genotoxic agents. In order to cope with this fundamental problem, all living organisms have acquired a complex network of DNA repair systems to safeguard their genetic integrity. Nucleotide excision repair (NER), one of the most important of these, is a complex multi-enzyme reaction that removes a remarkably wide range of lesions. This is the first of a series of two reviews on this repair process. Part I focuses on the main characteristics of the NER pathway in E. coli and yeast. Part II, to appear in the next issue of TIG, deals with NER in mammals and compares it with the process in yeast
The human RAD54 recombinational DNA repair protein is a double-stranded DNA-dependent ATPase
DNA double-strand break repair through the RAD52 homologous recombination
pathway in the yeast Saccharomyces cerevisiae requires, among others, the
RAD51, RAD52, and RAD54 genes. The biological importance of homologous
recombination is underscored by the conservation of the RAD52 pathway from
fungi to humans. The critical roles of the RAD52 group proteins in the
early steps of recombination, the search for DNA homology and strand
exchange, are now becoming apparent. Here, we report the purification of
the human Rad54 protein. We showed that human Rad54 has ATPase activity
that is absolutely dependent on double-stranded DNA. Unexpectedly, the
ATPase activity appeared not absolutely required for the DNA repair
function of human Rad54 in vivo. Despite the presence of amino acid
sequence motifs that are conserved in a large family of DNA helicases, no
helicase activity of human Rad54 was observed on a variety of different
DNA substrates. Possible functions of human Rad54 in homologous
recombination that couple the energy gained from ATP hydrolysis to
translocation along DNA, rather than disruption of base pairing, are
discussed
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