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   in Aging Neurons

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 extensi...

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Bibliographic Details
Published in:Neurochemical research 2004-04, Vol.29 (4), p.761-770
Main Authors: Krishna, T. Hari, Hemkal, Anjana, Rao, Kalluri Subba
Format: Article
Language:English
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Summary: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.
ISSN:0364-3190
1573-6903
DOI:10.1023/B:NERE.0000018848.58358.95