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Reduced DNA gap repair in aging rat neuronal extracts and its restoration by DNA polymerase β and DNA‐ligase
Author(s) -
Krishna T. Hari,
Mahipal S.,
Sudhakar A.,
Sugimoto H.,
Kalluri Raghu,
Rao K. Subba
Publication year - 2005
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02923.x
Subject(s) - dna ligase , dna polymerase , primer (cosmetics) , base excision repair , dna clamp , biology , dna repair , polymerase , microbiology and biotechnology , dna , dna polymerase mu , recombinant dna , dna polymerase delta , dna polymerase ii , nucleotide excision repair , biochemistry , chemistry , polymerase chain reaction , circular bacterial chromosome , gene , reverse transcriptase , organic chemistry
Synthetic deoxy‐oligo duplexes containing short gaps of 1 and 4 nucleotides were used as model substrates to assess the DNA gap repair ability of the neuronal extracts prepared from cerebral cortex of rats of different ages. Our results demonstrate that gap repair activity in neurons decreases markedly with age. The decreased activity could be restored by supplementing the neuronal extracts with pure recombinant rat liver DNA polymerase β. High levels of DNA polymerase β supplementation resulted in gap‐filling activity that proceeded essentially through addition of nucleotides through a slow distributive strand displacement mode to achieve full template length (32‐mer). However, at lower concentrations of DNA polymerase β, the gap repair takes place quickly through gap filling followed by ligation to downstream primer, in an energy efficient manner. For this to happen, the conditions required are the presence of 5′‐PO 4 on the downstream primer and supplementation of aging neuronal extracts with DNA‐ligase in addition to recombinant DNA polymerase β. These results demonstrate that aging neurons are unable to affect base excision repair (BER) due to deficiency of DNA polymerase β and DNA‐ligase and fortifying aged neuronal extracts with these two factors can restore the lost BER activity.