Complementary Functions of Plant AP Endonucleases and AP Lyases during DNA Repair of Abasic Sites Arising from C:G Base Pairs.

Abasic (apurinic/apyrimidinic, AP) sites are ubiquitous DNA lesions arising from spontaneous base loss and excision of damaged bases. They may be processed either by AP endonucleases or AP lyases, but the relative roles of these two classes of enzymes are not well understood. We hypothesized that endonucleases and lyases may be differentially influenced by the sequence surrounding the AP site and/or the identity of the orphan base.

Active DNA Demethylation in Plants.

Methylation of cytosine (5-meC) is a critical epigenetic modification in many eukaryotes, and genomic DNA methylation landscapes are dynamically regulated by opposed methylation and demethylation processes. Plants are unique in possessing a mechanism for active DNA demethylation involving DNA glycosylases that excise 5-meC and initiate its replacement with unmodified C through a base excision repair (BER) pathway. Plant BER-mediated DNA demethylation is a complex process involving numerous proteins, as well as additional regulatory factors that avoid accumulation of potentially harmful intermediates and coordinate demethylation and methylation to maintain balanced yet flexible DNA methylation patterns.

DNA Base Excision Repair in Plants: An Unfolding Story With Familiar and Novel Characters.

Base excision repair (BER) is a critical genome defense pathway that deals with a broad range of non-voluminous DNA lesions induced by endogenous or exogenous genotoxic agents. BER is a complex process initiated by the excision of the damaged base, proceeds through a sequence of reactions that generate various DNA intermediates, and culminates with restoration of the original DNA structure. BER has been extensively studied in microbial and animal systems, but knowledge in plants has lagged behind until recently.

Characterization of an AP endonuclease from sugarcane - ScARP1.

Plants are sessile organisms that need to cope with different conditions. The Base Excision Repair (BER) pathway is an important mechanism protecting the genome from DNA lesions. Apurinic/apyrimidinic (AP) endonucleases are key BER enzymes that process AP sites arising either spontaneously or as BER intermediates.

Characterization of a novel cysteine-rich antifungal protein from Fusarium graminearum with activity against maize fungal pathogens.

Filamentous fungi are an invaluable source for biocontrol strategies and for production and development of different antifungal polypeptides. Within this context, cysteine-rich antifungal AFP-like peptides stand out among many different antimicrobial compounds given their production easiness, stability, versatility, and efficacy. AFP from Aspergillus giganteus represents the hallmark of this still increasing family of antifungal polypeptides.

Monitoring base excision repair in Chlamydomonas reinhardtii cell extracts.

Base excision repair (BER) is a major defense pathway against spontaneous DNA damage. This multistep process is initiated by DNA glycosylases that recognise and excise the damaged base, and proceeds by the concerted action of additional proteins that perform incision of the abasic site, gap filling and ligation. BER has been extensively studied in bacteria, yeasts and animals.

Nonenzymatic release of N7-methylguanine channels repair of abasic sites into an AP endonuclease-independent pathway in .

Abasic (apurinic/apyrimidinic, AP) sites in DNA arise from spontaneous base loss or by enzymatic removal during base excision repair. It is commonly accepted that both classes of AP site have analogous biochemical properties and are equivalent substrates for AP endonucleases and AP lyases, although the relative roles of these two types of enzymes are not well understood. We provide here genetic and biochemical evidence that, in , AP sites generated by spontaneous loss of N7-methylguanine (N7-meG) are exclusively repaired through an AP endonuclease-independent pathway initiated by FPG, a bifunctional DNA glycosylase with AP lyase activity.

Dual control of ROS1-mediated active DNA demethylation by DNA damage-binding protein 2 (DDB2).

By controlling gene expression, DNA methylation contributes to key regulatory processes during plant development. Genomic methylation patterns are dynamic and must be properly maintained and/or re-established upon DNA replication and active removal, and therefore require sophisticated control mechanisms. Here we identify direct interplay between the DNA repair factor DNA damage-binding protein 2 (DDB2) and the ROS1-mediated active DNA demethylation pathway in Arabidopsis thaliana.

An AP endonuclease functions in active DNA demethylation and gene imprinting in Arabidopsis [corrected].

Active DNA demethylation in plants occurs through base excision repair, beginning with removal of methylated cytosine by the ROS1/DME subfamily of 5-methylcytosine DNA glycosylases. Active DNA demethylation in animals requires the DNA glycosylase TDG or MBD4, which functions after oxidation or deamination of 5-methylcytosine, respectively. However, little is known about the steps following DNA glycosylase action in the active DNA demethylation pathways in plants and animals.

Arabidopsis ZDP DNA 3'-phosphatase and ARP endonuclease function in 8-oxoG repair initiated by FPG and OGG1 DNA glycosylases.

Oxidation of guanine in DNA generates 7,8-dihydro-8-oxoguanine (8-oxoG), an ubiquitous lesion with mutagenic properties. 8-oxoG is primarily removed by DNA glycosylases distributed in two families, typified by bacterial Fpg proteins and eukaryotic Ogg1 proteins. Interestingly, plants possess both Fpg and Ogg1 homologs but their relative contributions to 8-oxoG repair remain uncertain.

The DNA repair protein XRCC1 functions in the plant DNA demethylation pathway by stimulating cytosine methylation (5-meC) excision, gap tailoring, and DNA ligation.

DNA methylation patterns are the dynamic outcome of antagonist methylation and demethylation mechanisms, but the latter are still poorly understood. Active DNA demethylation in plants is mediated by a family of DNA glycosylases typified by Arabidopsis ROS1 (repressor of silencing 1). ROS1 and its homologs remove 5-methylcytosine and incise the sugar backbone at the abasic site, thus initiating a base excision repair pathway that finally inserts an unmethylated cytosine.

Using Arabidopsis cell extracts to monitor repair of DNA base damage in vitro.

Base excision repair (BER) is a major pathway for the removal of endogenous and exogenous DNA damage. This repair mechanism is initiated by DNA glycosylases that excise the altered base, and continues through alternative routes that culminate in DNA resynthesis and ligation. In contrast to the information available for microbes and animals, our knowledge about this important DNA repair pathway in plants is very limited, partially due to a lack of biochemical approaches.

Arabidopsis ARP endonuclease functions in a branched base excision DNA repair pathway completed by LIG1.

Base excision repair (BER) is an essential cellular defence mechanism against DNA damage, but it is poorly understood in plants. We used an assay that monitors repair of damaged bases and abasic (apurinic/apyrimidinic, AP) sites in Arabidopsis to characterize post-excision events during plant BER. We found that Apurinic endonuclease-redox protein (ARP) is the major AP endonuclease activity in Arabidopsis cell extracts, and is required for AP incision during uracil BER in vitro.

Homologous recombination is stimulated by a decrease in dUTPase in Arabidopsis.

Deoxyuridine triphosphatase (dUTPase) enzyme is an essential enzyme that protects DNA against uracil incorporation. No organism can tolerate the absence of this activity. In this article, we show that dUTPase function is conserved between E.

Arabidopsis uracil DNA glycosylase (UNG) is required for base excision repair of uracil and increases plant sensitivity to 5-fluorouracil.

Uracil in DNA arises by misincorporation of dUMP during replication and by hydrolytic deamination of cytosine. This common lesion is actively removed through a base excision repair (BER) pathway initiated by a uracil DNA glycosylase (UDG) activity that excises the damage as a free base. UDGs are classified into different families differentially distributed across eubacteria, archaea, yeast, and animals, but remain to be unambiguously identified in plants.

Single-nucleotide and long-patch base excision repair of DNA damage in plants.

Base excision repair (BER) is a critical pathway in cellular defense against endogenous or exogenous DNA damage. This elaborate multistep process is initiated by DNA glycosylases that excise the damaged base, and continues through the concerted action of additional proteins that finally restore DNA to the unmodified state. BER has been subject to detailed biochemical analysis in bacteria, yeast and animals, mainly through in vitro reproduction of the entire repair reaction in cell-free extracts.

Influence of the chloride channel of Fusarium oxysporum on extracellular laccase activity and virulence on tomato plants.

CLC-type voltage-gated chloride channels are a family of proteins which mediate chloride transport across the plasma and intracellular membranes. A clc1 gene from the vascular wilt fungus Fusarium oxysporum was characterized and disrupted. The predicted Clc1 protein contained highly conserved transmembrane and CBS domains of this protein family and showed significant identities to the Saccharomyces cerevisiae GEF1 and the Cryptococcus neoformans CLC-A chloride channels.