This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Johnson, R. E. Articles by Prakash, S. Search for Related Content PubMed PubMed Citation Articles by Johnson, R. E. Articles by Prakash, S.

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

Robert E. Johnson, Lajos Haracska, 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 (Pol ) 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 with template A and incoming dTTP and with template G and incoming dCTP have revealed that in the Pol 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 , 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 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.

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

This article has been cited by other articles:

• 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]