Novel mutator mutants of E-coli nrdAB ribonucleotide reductase: Insight into allosteric regulation and control of mutation rates

Laboratory of Molecular Genetics, National Institute of Environmental and Health Sciences, 111 TW Alexander Drive, Research Triangle Park, NC 27709, USA.
DNA repair (Impact Factor: 3.11). 03/2012; 11(5):480-7. DOI: 10.1016/j.dnarep.2012.02.001
Source: PubMed


Ribonucleotide reductase (RNR) is the enzyme critically responsible for the production of the 5'-deoxynucleoside-triphosphates (dNTPs), the direct precursors for DNA synthesis. The dNTP levels are tightly controlled to permit high efficiency and fidelity of DNA synthesis. Much of this control occurs at the level of the RNR by feedback processes, but a detailed understanding of these mechanisms is still lacking. Using a genetic approach in the bacterium Escherichia coli, a paradigm for the class Ia RNRs, we isolated 23 novel RNR mutants displaying elevated mutation rates along with altered dNTP levels. The responsible amino-acid substitutions in RNR reside in three different regions: (i) the (d)ATP-binding activity domain, (ii) a novel region in the small subunit adjacent to the activity domain, and (iii) the dNTP-binding specificity site, several of which are associated with different dNTP pool alterations and different mutational outcomes. These mutants provide new insight into the precise mechanisms by which RNR is regulated and how dNTP pool disturbances resulting from defects in RNR can lead to increased mutation.

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Available from: Rachelle J Bienstock, Dec 18, 2013
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    • "As the mismatch extension step competes directly with the removal of the erroneous base by proofreading, elevated dNTPs can be mutagenic through this mechanism. When the specific changes in the dNTP pool mutants are known, clear predictions can be made as to the mispairings that will be promoted [19] [21]. These predictions can then be used to " mark " the strands and to verify the earlier conclusion that lagging strand replication is more accurate than leading-strand replication. "
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