Substrate-Dependent Millisecond Domain Motions in DNA Polymerase I2

DNA polymerase I2 (Pol I2) is a 39-kDa enzyme that performs the vital cellular function of repairing damaged DNA. Mutations in Pol I2 have been linked to various cancers, and these mutations are further correlated with altered Pol I2 enzymatic activity. The fidelity of correct nucleotide incorporati...

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Published in:Journal of molecular biology 2012-06, Vol.419 (3-4), p.171-182
Main Authors: Berlow, Rebecca B, Swain, Monalisa, Dalal, Shibani, Sweasy, Joann B, Loria, JPatrick
Format: Article
Language:English
Online Access:Get full text
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Summary:DNA polymerase I2 (Pol I2) is a 39-kDa enzyme that performs the vital cellular function of repairing damaged DNA. Mutations in Pol I2 have been linked to various cancers, and these mutations are further correlated with altered Pol I2 enzymatic activity. The fidelity of correct nucleotide incorporation into damaged DNA is essential for Pol I2 repair function, and several studies have implicated conformational changes in Pol I2 as a determinant of this repair fidelity. In this work, the rate constants for domain motions in Pol I2 have been determined by solution NMR relaxation dispersion for the apo and substrate-bound, binary forms of Pol I2. In apo Pol I2, molecular motions, primarily isolated to the DNA lyase domain, are observed to occur at 1400 sa 1. Additional analysis suggests that these motions allow apo Pol I2 to sample a conformation similar to the gapped DNA-substrate-bound form. Upon binding DNA, these lyase domain motions are significantly quenched, whereas evidence for conformational motions in the polymerase domain becomes apparent. These NMR studies suggest an alteration in the dynamic landscape of Pol I2 due to substrate binding. Moreover, a number of the flexible residues identified in this work are also the location of residues, which upon mutation lead to cancer phenotypes in vivo, which may be due to the intimate role of protein motions in Pol I2 fidelity.
ISSN:0022-2836
DOI:10.1016/j.jmb.2012.03.013