Related Research Articles
The SOS response is a global response to DNA damage in which the cell cycle is arrested and DNA repair and mutagenesis is induced. The system involves the RecA protein. The RecA protein, stimulated by single-stranded DNA, is involved in the inactivation of the repressor (LexA) of SOS response genes thereby inducing the response. It is an error-prone repair system that contributes significantly to DNA changes observed in a wide range of species.
DNA glycosylases are a family of enzymes involved in base excision repair, classified under EC number EC 3.2.2. Base excision repair is the mechanism by which damaged bases in DNA are removed and replaced. DNA glycosylases catalyze the first step of this process. They remove the damaged nitrogenous base while leaving the sugar-phosphate backbone intact, creating an apurinic/apyrimidinic site, commonly referred to as an AP site. This is accomplished by flipping the damaged base out of the double helix followed by cleavage of the N-glycosidic bond.
The adaptive response is a form of direct DNA repair in E. coli that protects DNA from damage by external agents or by errors during replication. It is initiated against alkylation, particularly methylation, of guanine or thymine nucleotides or phosphate groups on the sugar-phosphate backbone of DNA. Under sustained exposure to low-level treatment with alkylating mutagens, E. coli can adapt to the presence of the mutagen, rendering subsequent treatment with high doses of the same agent less effective.
In genetics, crosslinking of DNA occurs when various exogenous or endogenous agents react with two nucleotides of DNA, forming a covalent linkage between them. This crosslink can occur within the same strand (intrastrand) or between opposite strands of double-stranded DNA (interstrand). These adducts interfere with cellular metabolism, such as DNA replication and transcription, triggering cell death. These crosslinks can, however, be repaired through excision or recombination pathways.
AlkB (Alkylation B) is a protein found in E. coli, induced during an adaptive response and involved in the direct reversal of alkylation damage. AlkB specifically removes alkylation damage to single stranded (SS) DNA caused by SN2 type of chemical agents. It efficiently removes methyl groups from 1-methyl adenines, 3-methyl cytosines in SS DNA. AlkB is an alpha-ketoglutarate-dependent hydroxylase, a superfamily non-haem iron-containing proteins. It oxidatively demethylates the DNA substrate. Demethylation by AlkB is accompanied with release of CO2, succinate, and formaldehyde.
Deoxyribonuclease IV (phage-T4-induced) is catalyzes the degradation nucleotides in DsDNA by attacking the 5'-terminal end.
In enzymology, a methylated-DNA-[protein]-cysteine S-methyltransferase is an enzyme that catalyzes the chemical reaction
The enzyme DNA-(apurinic or apyrimidinic site) lyase, also referred to as DNA-(apurinic or apyrimidinic site) 5'-phosphomonoester-lyase or DNA AP lyase catalyzes the cleavage of the C-O-P bond 3' from the apurinic or apyrimidinic site in DNA via β-elimination reaction, leaving a 3'-terminal unsaturated sugar and a product with a terminal 5'-phosphate. In the 1970s, this class of enzyme was found to repair at apurinic or apyrimidinic DNA sites in E. coli and in mammalian cells. The major active enzyme of this class in bacteria, and specifically, E. coli is endonuclease type III. This enzyme is part of a family of lyases that cleave carbon-oxygen bonds.
DNA polymerase beta, also known as POLB, is an enzyme present in eukaryotes. In humans, it is encoded by the POLB gene.
DNA-3-methyladenine glycosylase also known as 3-alkyladenine DNA glycosylase (AAG) or N-methylpurine DNA glycosylase (MPG) is an enzyme that in humans is encoded by the MPG gene.
Endonuclease III-like protein 1 is an enzyme that in humans is encoded by the NTHL1 gene.
Tomas Robert Lindahl FRS FMedSci is a Swedish-British scientist specialising in cancer research. In 2015, he was awarded the Nobel Prize in Chemistry jointly with American chemist Paul L. Modrich and Turkish chemist Aziz Sancar for mechanistic studies of DNA repair.
In molecular biology, the BolA-like protein family consists of the morpho-protein BolA from Escherichia coli, the Fra2 protein from Saccharomyces cerevisiae, and various homologs. The BolA protein is a DNA-binding regulator; the Fra2 protein is an iron sulfur cluster protein that binds Grx3/4 and is involved in regulating iron levels .
In DNA repair, the Ada regulon is a set of genes whose expression is essential to adaptive response, which is triggered in prokaryotic cells by exposure to sub-lethal doses of alkylating agents. This allows the cells to tolerate the effects of such agents, which are otherwise toxic and mutagenic.
DNA oxidative demethylase (EC 1.14.11.33, alkylated DNA repair protein, alpha-ketoglutarate-dependent dioxygenase ABH1, alkB (gene)) is an enzyme with systematic name methyl DNA-base, 2-oxoglutarate:oxygen oxidoreductase (formaldehyde-forming). This enzyme catalyses the following chemical reaction
DNA-3-methyladenine glycosylase I is an enzyme with systematic name alkylated-DNA glycohydrolase . This enzyme catalyses the following chemical reaction
DNA-formamidopyrimidine glycosylase is an enzyme with systematic name DNA glycohydrolase . FPG is a base excision repair enzyme which recognizes and removes a wide range of oxidized purines from correspondingly damaged DNA. It was discovered by Zimbabwean scientist Christopher J. Chetsanga in 1975.
Double-stranded uracil-DNA glycosylase is an enzyme with systematic name uracil-double-stranded DNA deoxyribohydrolase (uracil-releasing). This enzyme catalyses a specific chemical reaction: it hydrolyses mismatched double-stranded DNA and polynucleotides, releasing free uracil.
AlkD is an enzyme belonging to a family of DNA glycosylases that are involved in DNA repair. It was discovered by a team of Norwegian biologists from Oslo in 2006. It was isolated from a soil-dwelling Gram-positive bacteria Bacillus cereus, along with another enzyme AlkC. AlkC and AlkD are most probably derived from the same protein as indicated by their close resemblance. They are also found in other prokaryotes. Among eukaryotes, they are found only in the single-celled species only, such as Entamoeba histolytica and Dictyostelium discoideum. The enzyme specifically targets 7mG (methyl-guanine) in the DNA, and is, therefore, unique among DNA glycosylases. It can also act on other methylpurines with less affinity. It indicates that the enzyme is specific for locating and cutting (excision) of chemically modified bases from DNA, exactly at 7mG, whenever there are errors in replication. It accelerates the rate of 7mG hydrolysis 100-fold over the spontaneous depurination. Thus, it protects the genome from harmful changes induced by chemical and environmental agents. Its crystal structure was described in 2008. It is the first HEAT repeat protein identified to interact with nucleic acids or to contain enzymatic activity.
Christopher J. Chetsanga is a prominent Zimbabwean scientist who is a member of the African Academy of Sciences and The World Academy of Sciences. He discovered two enzymes involved in DNA repair. He has also held various academic administrative posts like Vice-Chancellor, Director and Dean.
References
- ↑ Evensen G, Seeberg E (April 1982). "Adaptation to alkylation resistance involves the induction of a DNA glycosylase". Nature. 296 (5859): 773–775. Bibcode:1982Natur.296..773E. doi:10.1038/296773a0. PMID 7040984. S2CID 4318955.
- ↑ Karran P, Hjelmgren T, Lindahl T (April 1982). "Induction of a DNA glycosylase for N-methylated purines is part of the adaptive response to alkylating agents". Nature. 296 (5859): 770–773. Bibcode:1982Natur.296..770K. doi:10.1038/296770a0. PMID 7040983. S2CID 4367726.
- ↑ Riazuddin S, Lindahl T (May 1978). "Properties of 3-methyladenine-DNA glycosylase from Escherichia coli". Biochemistry. 17 (11): 2110–2118. doi:10.1021/bi00604a014. PMID 352392.
- ↑ Thomas L, Yang CH, Goldthwait DA (March 1982). "Two DNA glycosylases in Escherichia coli which release primarily 3-methyladenine". Biochemistry. 21 (6): 1162–1169. doi:10.1021/bi00535a009. PMID 7041972.
- ↑ Krokan HE, Bjørås M (April 2013). "Base excision repair". Cold Spring Harbor Perspectives in Biology. 5 (4): a012583. doi:10.1101/cshperspect.a012583. PMC 3683898 . PMID 23545420.
