KINETIC STUDIES OF TWO ERROR-PRONE DNA REPAIR ENZYMES: POSSIBLE MECHANISMS FOR VIRAL MUTAGENESIS

 
 
 
 

KINETIC STUDIES OF TWO ERROR-PRONE DNA REPAIR ENZYMES: POSSIBLE MECHANISMS FOR VIRAL MUTAGENESIS

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Title: KINETIC STUDIES OF TWO ERROR-PRONE DNA REPAIR ENZYMES: POSSIBLE MECHANISMS FOR VIRAL MUTAGENESIS
Author: Showalter, Alexander Keith
Description: This work describes the kinetic characterization of two DNA processing enzymes from the African Swine Fever Virus. The two enzymes, a DNA polymerase and a DNA ligase, have been predicted on the basis of sequence homology to function in repair of the viral genome during infection. Such a role would suggest that the viral DNA polymerase, like most other DNA polymerases, selectively catalyzes the formation of Watson-Crick, as opposed to mismatched, base pairs. The pre-steady-state kinetic analysis described in this work, however, indicates that the viral DNA polymerase is among the most error-prone known, with equivalent catalytic efficiencies for formation of the G:C Watson-Crick base pair and the G:G mismatched base pair. It is thus proposed that this polymerase operates in a mutagenic repair pathway, in which the viral response to chemical damage to its DNA includes the introduction of point mutations. One prediction put forth on the basis of this hypothesis is that the viral DNA ligase would have an attenuated ability to discriminate against substrates containing a mismatched base pair; the products of error-prone synthesis by the polymerase. This prediction is supported by steady-state kinetic analysis of the viral ligase, whose ability to discriminate between a nicked substrate containing all Watson-Crick base pairs versus a substrate containing a G:G mismatch is decreased by at least 2-3 orders of magnitude relative to that of bacteriophage T4 DNA ligase. Verification of the prediction is taken as preliminary support of the mutagenic viral DNA repair pathway. Further mechanistic and biological implications of these findings are considered.
Permanent Link: http://rave.ohiolink.edu/etdc/view?acc_num=osu1016207119
http://hdl.handle.net/2374.OX/4628
Date: 2002

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