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Translesion Synthesis (translesion + synthesis)

Distribution by Scientific Domains

Life Sciences	60%
Chemistry	30%

Selected Abstracts

Translesion Synthesis of 1,3-GTG Cisplatin DNA Lesions

CHEMBIOCHEM, Issue 11 2010
Sabine Schneider Dr.
Low-fidelity polymerases: Cells can copy genetic material even in the presence of DNA lesions. Here we show that this bypass process is also possible for the strongly helix disturbing cisplatin 1,3-GTG lesion. A key polymerase involved in the translesion synthesis (TLS) process is Pol ,. The results have implication for the resistance problem associated with cisplatin chemotherapy. [source]

Molecular genetics of Xeroderma pigmentosum variant

EXPERIMENTAL DERMATOLOGY, Issue 5 2003
Alexei Gratchev
Skin abnormalities result from an inability to repair UV-damaged DNA because of defects in the nucleotide excision repair (NER) machinery. Xeroderma pigmentosum is genetically heterogeneous and is classified into seven complementation groups (XPA-XPG) that correspond to genetic alterations in one of seven genes involved in NER. The variant type of XP (XPV), first described in 1970 by Ernst G. Jung as ,pigmented xerodermoid', is caused by defects in the post replication repair machinery while NER is not impaired. Identification of the XPV gene was only achieved in 1999 by biochemical purification and sequencing of a protein from HeLa cell extracts complementing the PRR defect in XPV cells. The XPV protein, polymerase (pol),, represents a novel member of the Y family of bypass DNA polymerases that facilitate DNA translesion synthesis. The major function of pol, is to allow DNA translesion synthesis of UV-induced TT-dimers in an error-free manner; it also possesses the capability to bypass other DNA lesions in an error-prone manner. Xeroderma pigmentosum V is caused by molecular alterations in the POLH gene, located on chromosome 6p21.1,6p12. Affected individuals are homozygous or compound heterozygous for a spectrum of genetic lesions, including nonsense mutations, deletions or insertions, confirming the autosomal recessive nature of the condition. Identification of POLH as the XPV gene provides an important instrument for improving molecular diagnostics in XPV families. [source]

Identification of a novel REV1-interacting motif necessary for DNA polymerase , function

GENES TO CELLS, Issue 2 2009
Eiji Ohashi
When a replicative DNA polymerase (Pol) is stalled by damaged DNA, a "polymerase switch" recruits specialized translesion synthesis (TLS) DNA polymerase(s) to sites of damage. Mammalian cells have several TLS DNA polymerases, including the four Y-family enzymes (Pol,, Pol,, Pol, and REV1) that share multiple primary sequence motifs, but show preferential bypass of different DNA lesions. REV1 interacts with Pol,, Pol,, and Pol, and therefore appears to play a central role during TLS in vivo. Here we have investigated the molecular basis for interactions between REV1 and Pol,. We have identified novel REV1-interacting regions (RIRs) present in Pol,, Pol, and Pol,. Within the RIRs, the presence of two consecutive phenylalanines (FF) is essential for REV1-binding. The consensus sequence for REV1-binding is denoted by x-x-x-F-F-y-y-y-y (x, no specific residue and y, no specific residue but not proline). Our results identify structural requirements that are necessary for FF-flanking residues to confer interactions with REV1. A Pol, mutant lacking REV1-binding activity did not complement the genotoxin-sensitivity of Polk -null mouse embryonic fibroblast cells, thereby demonstrating that the REV1-interaction is essential for Pol, function in vivo. [source]

DNA binding properties of human DNA polymerase ,: implications for fidelity and polymerase switching of translesion synthesis

GENES TO CELLS, Issue 12 2004
Rika Kusumoto
The human XPV (xeroderma pigmentosum variant) gene is responsible for the cancer,prone xeroderma pigmentosum syndrome and encodes DNA polymerase , (pol ,), which catalyses efficient translesion synthesis past cis -syn cyclobutane thymine dimers (TT dimers) and other lesions. The fidelity of DNA synthesis by pol , on undamaged templates is extremely low, suggesting that pol , activity must be restricted to damaged sites on DNA. Little is known, however, about how the activity of pol , is targeted and restricted to damaged DNA. Here we show that pol , binds template/primer DNAs regardless of the presence of TT dimers. Rather, enhanced binding to template/primer DNAs containing TT dimers is only observed when the 3,-end of the primer is an adenosine residue situated opposite the lesion. When two nucleotides have been incorporated into the primer beyond the TT dimer position, the pol ,-template/primer DNA complex is destabilized, allowing DNA synthesis by DNA polymerases , or , to resume. Our study provides mechanistic explanations for polymerase switching at TT dimer sites. [source]

Biological roles of translesion synthesis DNA polymerases in eubacteria

MOLECULAR MICROBIOLOGY, Issue 3 2010
Dan I. Andersson
Summary Biological systems are strongly selected to maintain the integrity of their genomes by prevention and repair of external and internal DNA damages. However, some types of DNA lesions persist and might block the replication apparatus. The universal existence of specialized translesion synthesis DNA polymerases (TLS polymerases) that can bypass such lesions in DNA implies that replication blockage is a general biological problem. We suggest that the primary function for which translesion synthesis polymerases are selected is to rescue cells from replication arrest at lesions in DNA, a situation that, if not amended, is likely to cause an immediate and severe reduction in cell fitness and survival. We will argue that the mutagenesis observed during translesion synthesis is an unavoidable secondary consequence of this primary function and not, as has been suggested, an evolved mechanism to increase mutation rates in response to various stresses. Finally, we will discuss recent data on additional roles for translesion synthesis polymerases in the formation of spontaneous deletions and in transcription-coupled TLS, where the coupling of transcription to TLS is proposed to allow the rescue of the transcription machinery arrested at DNA lesions. [source]

The processing of a Benzo(a)pyrene adduct into a frameshift or a base substitution mutation requires a different set of genes in Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 2 2000
Nathalie Lenne-Samuel
Replication through a single DNA lesion may give rise to a panel of translesion synthesis (TLS) events, which comprise error-free TLS, base substitutions and frameshift mutations. In order to determine the genetic control of the various TLS events induced by a single lesion, we have chosen the major N2-dG adduct of (+)- anti -Benzo(a)pyrene diol epoxide [(+)- anti -BPDE] adduct located within a short run of guanines as a model lesion. Within this sequence context, in addition to the major event, i.e. error-free TLS, the adduct also induces base substitutions (mostly G , T transversions) and ,1 frameshift mutations. The pathway leading to G , T base substitution mutagenesis appears to be SOS independent, suggesting that TLS is most probably performed by the replicative Pol III holoenzyme itself. In contrast, both error-free and frameshift TLS pathways are dependent upon SOS-encoded functions that belong to the pool of inducible DNA polymerases specialized in TLS (translesional DNA polymerases), namely umuDC (Pol V) and dinB (Pol IV). It is likely that, given the diversity of conformations that can be adopted by lesion-containing replication intermediates, cells use one or several translesional DNA polymerases to achieve TLS. [source]

Arabidopsis thaliana Y-family DNA polymerase , catalyses translesion synthesis and interacts functionally with PCNA2

THE PLANT JOURNAL, Issue 6 2008
Heather J. Anderson
Summary Upon blockage of chromosomal replication by DNA lesions, Y-family polymerases interact with monoubiquitylated proliferating cell nuclear antigen (PCNA) to catalyse translesion synthesis (TLS) and restore replication fork progression. Here, we assessed the roles of Arabidopsis thaliana POLH, which encodes a homologue of Y-family polymerase , (Pol,), PCNA1 and PCNA2 in TLS-mediated UV resistance. A T-DNA insertion in POLH sensitized the growth of roots and whole plants to UV radiation, indicating that AtPol, contributes to UV resistance. POLH alone did not complement the UV sensitivity conferred by deletion of yeast RAD30, which encodes Pol,, although AtPol, exhibited cyclobutane dimer bypass activity in vitro, and interacted with yeast PCNA, as well as with Arabidopsis PCNA1 and PCNA2. Co-expression of POLH and PCNA2, but not PCNA1, restored normal UV resistance and mutation kinetics in the rad30 mutant. A single residue difference at site 201, which lies adjacent to the residue (lysine 164) ubiquitylated in PCNA, appeared responsible for the inability of PCNA1 to function with AtPol, in UV-treated yeast. PCNA-interacting protein boxes and an ubiquitin-binding motif in AtPol, were found to be required for the restoration of UV resistance in the rad30 mutant by POLH and PCNA2. These observations indicate that AtPol, can catalyse TLS past UV-induced DNA damage, and links the biological activity of AtPol, in UV-irradiated cells to PCNA2 and PCNA- and ubiquitin-binding motifs in AtPol,. [source]

A charged residue at the subunit interface of PCNA promotes trimer formation by destabilizing alternate subunit interactions

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2009
Bret D. Freudenthal
Eukaryotic proliferating cell nuclear antigen (PCNA) is an essential replication accessory factor that interacts with a variety of proteins involved in DNA replication and repair. Each monomer of PCNA has an N-terminal domain A and a C-terminal domain B. In the structure of the wild-type PCNA protein, domain A of one monomer interacts with domain B of a neighboring monomer to form a ring-shaped trimer. Glu113 is a conserved residue at the subunit interface in domain A. Two distinct X-ray crystal structures have been determined of a mutant form of PCNA with a substitution at this position (E113G) that has previously been studied because of its effect on translesion synthesis. The first structure was the expected ring-shaped trimer. The second structure was an unanticipated nontrimeric form of the protein. In this nontrimeric form, domain A of one PCNA monomer interacts with domain A of a neighboring monomer, while domain B of this monomer interacts with domain B of a different neighboring monomer. The B,B interface is stabilized by an antiparallel ,-sheet and appears to be structurally similar to the A,B interface observed in the trimeric form of PCNA. The A,A interface, in contrast, is primarily stabilized by hydrophobic interactions. Because the E113G substitution is located on this hydrophobic surface, the A,A interface should be less favorable in the case of the wild-type protein. This suggests that the side chain of Glu113 promotes trimer formation by destabilizing these possible alternate subunit interactions. [source]