title: The presence of 3'-5' exonuclease activity in rat brain neurons and its role in template-driven extension of 3'-mismatched primers by DNA-polymerase beta in aging neurons.
abstract: A three-step reaction strategy has been developed to examine the mechanism of extension of a mismatched primer in an oligoduplex substrate by rat neuronal extracts and DNA polymerase beta. The results revealed that in the case of duplexes with a mismatch at 3'-end of primer, significant extension by DNA polymerase beta has taken place only after the removal of the mismatched base, thus indicating the presence of a proof reading 3'-5' exonuclease activity in neuronal extracts of all ages. A closer examination of the neuronal exonuclease activity revealed that bases are excised from the 3' end in a sequential and nonspecific manner, although initial excision of a mismatched base was slightly faster. Further, the excision efficiency is seen to decrease with the age of the animal but apparently does not go below a critical level so as to become a rate-limiting factor for the DNA-repair activity.
authors.affiliation: ICMR-Advanced Center for Research on Aging and Brain, Department of Biochemistry, University of Hyderabad, Hyderabad, India.
authors.forename: T Hari
authors.initials: TH
authors.lastname: Krishna
authors.forename: Anjana
authors.initials: A
authors.lastname: Hemkal
authors.forename: Kalluri Subba
authors.initials: KS
authors.lastname: Rao
mesh_terms: D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D019951:DNA Polymerase beta / Q000378:metabolism; D017931:DNA Primers; D005092:Exonucleases / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D013698:Templates, Genetic
chemical_list: D017931:DNA Primers; D019951:DNA Polymerase beta; D005092:Exonucleases