Repair of alkylated DNA: Recent advances
ABSTRACT Cytotoxic and mutagenic methylated bases in DNA can be generated by endogenous and environmental alkylating agents. Such damaged bases are removed by three distinct strategies. The abundant toxic lesion 3-methyladenine (3-alkyladenine) is excised by a specific DNA glycosylase that initiates a base excision-repair process. The toxic lesions 1-methyladenine and 3-methylcytosine are corrected by oxidative DNA demethylation catalyzed by DNA dioxygenases. These enzymes release the methyl moiety as formaldehyde, directly reversing the base damage. The third strategy involves the mutagenic and cytotoxic lesion O(6)-methylguanine which is also repaired by direct reversal but uses a different mechanism. Here, the methyl group is transferred from the lesion to a specific cysteine residue within the methyltransferase itself. In this review, we briefly describe endogenous alkylating agents and the extensively investigated DNA repair enzymes, mammalian 3-methyladenine-DNA glycosylase and O(6)-methylguanine-DNA methyltransferase. We provide a more detailed description of the structures and biochemical properties of the recently discovered DNA dioxygenases.
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ABSTRACT: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein with diverse biological functions in human cells. In bacteria, moonlighting GAPDH functions have only been described for the secreted protein in pathogens or probiotics. At the intracellular level, we previously reported the interaction of Escherichia coli GAPDH with phosphoglycolate phosphatase, a protein involved in the metabolism of the DNA repair product 2-phosphoglycolate, thus suggesting a putative role of GAPDH in DNA repair processes. Here, we provide evidence that GAPDH is required for the efficient repair of DNA lesions in E. coli. We show that GAPDH-deficient cells are more sensitive to bleomycin or methyl methanesulfonate. In cells challenged with these genotoxic agents GAPDH deficiency results in reduced cell viability and filamentous growth. In addition, the gapA knockout mutant accumulates a higher number of spontaneous abasic sites and displays higher spontaneous mutation frequencies than the parental strain. Pull-down experiments in different genetic backgrounds show interaction between GAPDH and enzymes of the base excision repair pathway, namely the AP-endonuclease Endo IV and uracil DNA glycosylase. This finding suggests that GAPDH is a component of a protein complex dedicated to the maintenance of genomic DNA integrity. Our results also show interaction of GAPDH with the single-stranded DNA binding protein. This interaction may recruit GAPDH to the repair sites and implicates GAPDH in DNA repair pathways activated by profuse DNA damage, such as homologous recombination or the SOS response.The International Journal of Biochemistry & Cell Biology 01/2015; 12. DOI:10.1016/j.biocel.2015.01.008 · 4.24 Impact Factor
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ABSTRACT: Abstract A tandemly repeated C-terminal domain (CTD) of the largest subunit of RNA polymerase II is functionally essential and strongly conserved in many organisms, including animal, yeast and plant models. Although present in simple, ancestral red algae, CTD tandem repeats have undergone extensive modifications and degeneration during the evolutionary transition to developmentally complex rhodophytes. In contrast, CTD repeats are conserved in both green algae and their more complex land plant relatives. Understanding the mechanistic differences that underlie these variant patterns of CTD evolution requires knowledge of CTD-associated proteins in these two lineages. To provide an initial baseline comparison, we bound potential phospho-CTD associated proteins (PCAPs) to artificially synthesized and phosphorylated CTD repeats from the unicellular red alga Cyanidioschyzon merolae and green alga Chlamydomonas reinhardtii. Our results indicate that red and green algae share a number of PCAPs, including kinases and proteins involved in mRNA export. There also are important taxon-specific differences, including mRNA splicing-related PCAPs recovered from Chlamydomonas but not Cyanidioschyzon, consistent with the relative intron densities in green and red algae. Our results also offer the first experimental indication that different proteins bind two distinct types of repeats in Cyanidioschyzon, suggesting a division of function between the proximal and distal CTD, similar to patterns identified in more developmentally complex model organisms.10/2014; 5(5). DOI:10.4161/21541264.2014.970944
Article: Stress-Induced Mutagenesis01/2012; 4(4). DOI:10.1128/ecosalplus.7.2.3