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Molecular and Cellular Biology, September 2006, p. 6435-6441, Vol. 26, No. 17
0270-7306/06/$08.00+0     doi:10.1128/MCB.00851-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Role of Hoogsteen Edge Hydrogen Bonding at Template Purines in Nucleotide Incorporation by Human DNA Polymerase {iota}

Robert E. Johnson, Lajos Haracska,{dagger} Louise Prakash, and Satya Prakash*

Sealy Center for Molecular Science, University of Texas Medical Branch at Galveston, 6.104 Blocker Medical Research Building, 11th and Mechanic Streets, Galveston, Texas 77555-1061

Received 12 May 2006/ Returned for modification 14 June 2006/ Accepted 20 June 2006

Human DNA polymerase {iota} (Pol {iota}) differs from other DNA polymerases in that it exhibits a marked template specificity, being more efficient and accurate opposite template purines than opposite pyrimidines. The crystal structures of Pol {iota} with template A and incoming dTTP and with template G and incoming dCTP have revealed that in the Pol {iota} active site, the templating purine adopts a syn conformation and forms a Hoogsteen base pair with the incoming pyrimidine which remains in the anti conformation. By using 2-aminopurine and purine as the templating residues, which retain the normal N7 position but lack the N6 of an A or the O6 of a G, here we provide evidence that whereas hydrogen bonding at N6 is dispensable for the proficient incorporation of a T opposite template A, hydrogen bonding at O6 is a prerequisite for C incorporation opposite template G. To further analyze the contributions of O6 and N7 hydrogen bonding to DNA synthesis by Pol {iota}, we have examined its proficiency for replicating through the 6O-methyl guanine and 8-oxoguanine lesions, which affect the O6 and N7 positions of template G, respectively. We conclude from these studies that for proficient T incorporation opposite template A, only the N7 hydrogen bonding is required, but for proficient C incorporation opposite template G, hydrogen bonding at both the N7 and O6 is an imperative. The dispensability of N6 hydrogen bonding for proficient T incorporation opposite template A has important biological implications, as that would endow Pol {iota} with the ability to replicate through lesions which impair the Watson-Crick hydrogen bonding potential at both the N1 and N6 positions of templating A.

* Corresponding author. Mailing address: Sealy Center for Molecular Science, University of Texas Medical Branch at Galveston, 6.104 Blocker Medical Research Building, 11th and Mechanic Streets, Galveston, TX 77555-1061. Phone: (409) 747-8602. Fax: (409) 747-8608. E-mail: s.prakash{at}utmb.edu.

{dagger} Present address: Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary.

Molecular and Cellular Biology, September 2006, p. 6435-6441, Vol. 26, No. 17
0270-7306/06/$08.00+0     doi:10.1128/MCB.00851-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Donny-Clark, K., Broyde, S. (2009). Influence of local sequence context on damaged base conformation in human DNA polymerase {iota}: molecular dynamics studies of nucleotide incorporation opposite a benzo[a]pyrene-derived adenine lesion. Nucleic Acids Res 0: gkp745v1-gkp745 [Abstract] [Full Text]  
  • Pence, M. G., Blans, P., Zink, C. N., Hollis, T., Fishbein, J. C., Perrino, F. W. (2009). Lesion Bypass of N2-Ethylguanine by Human DNA Polymerase {iota}. J. Biol. Chem. 284: 1732-1740 [Abstract] [Full Text]  
  • Johnson, R. E., Yu, S.-L., Prakash, S., Prakash, L. (2007). A Role for Yeast and Human Translesion Synthesis DNA Polymerases in Promoting Replication through 3-Methyl Adenine. Mol. Cell. Biol. 27: 7198-7205 [Abstract] [Full Text]  
  • Frank, E. G., Woodgate, R. (2007). Increased Catalytic Activity and Altered Fidelity of Human DNA Polymerase {iota} in the Presence of Manganese. J. Biol. Chem. 282: 24689-24696 [Abstract] [Full Text]  


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