The Akman lab is interested in DNA damage, mutagenesis, and genomic instability.  We use a human cell mutation reporting plasmid in which to site-specifically place chemically synthesized DNA base adducts in the tRNA gene supF.  These constructs allow us to analyze the biology of specific well characterized DNA base adducts with regard to their mutagenic potential and modes of repair.  Currently, we are studying N2-ethyl and isopropyl deoxyguanosine and N6-isopropyl deoxyadenosine adducts that result from exposure of DNA to alkylating carcinogens.

Additionally, in collaboration with the Vaughn lab we are interested in the role of unusual non-Watson-Crick DNA structures in fostering genomic instability.  We have identified, purified, and expressed an enzyme from rapidly replicating human cells that recognizes and resolves Hoogsteen bonded quadruplex DNA.  We are currently exploring the biologic roles of this enzyme in: (1) maintaining genomic stability of polydeoxyguanidylate containing regions of DNA, e.g., the telomere, and (2) modulating transcription of replication-associated genes, e.g., c-myc.

Competition of unlabelled structures in standard G4-DNA resolvase assay shows that recombinant G4-DNA resolvase has approximately 300-fold greater specificity for G4-DNA than potential duplex helicase substrates. a, An illustrative G4-DNA resolvase assay on non-denaturing PAGE with increasing amounts of unlabelled competing DNA structures. Lanes 1-7 correspond to 0, equimolar, 3-fold, 10-fold, 30-fold, 100-fold, or 300-fold molar excess of unlabelled competitor, respectively. b, Graphic representation of change in G4-DNA resolvase activity caused by unlabelled competitors (Mean ± S.D. of percent change in activity compared to no competitor, reactions set up in triplicate; S.D. < 1% in all cases). Percent of activity is measured by the amount of monomer produced with competitor normalized to amount of monomer formed without competitor.

Publications (selected): 

Harrington C., Lan Y., Akman  S.A.  The identification and characterization of a G4-DNA resolvase activity.  J. Biol. Chem. 272:24631-24636, 1997.

Waters, S.B., Akman, S.A.: A new assay to quantify in vivo repair of G:T mispairs by base excision repair.  Mutat. Res. 487:109-119, 2001.

Dai, J, Park, G, Wright, MW, Adams, M, Akman, SA, Manderville, RA: Detection and characterization of a glutathione conjugate of Ochratoxin A.  Chem. Res. Tox. 15:1581-1588, 2002.

Manderville, R.A., Calcutt, M.W., Dai, J., Park, G., Gillman, I.G., Noflte, R.E., Mohammed, A.K., Dizdaroglu, M., Rodriguez, H., Akman, S.A. Stoichiometric preference in copper-promoted oxidative DNA damage by Ochratoxin A.  Implications for DNA strand scission by a dicopper complex.  J. Inorg. Biochem. 95:87-96, 2003.

Perrino, FW, Blans, P, Harvey, S, Gelhaus, SL, McGrath, C, Akman, SA, Jenkins, GS, LaCourse, WR, Fishbein, JC: The N²-ethylguanine and the O⁶-ethyl- and O⁶-methylguanine lesions in DNA: contrasting responses from the "bypass" DNA polymerase eta and the replicative DNA polymerase alpha. Chem. Res. Toxicol., 16:1616-1623, 2003.

Hart LS, Yannone, SM, Naczki, CC, Orlando, JS, Waters, SB, Akman, SA, Chen, DJ, Ornelles, D, and Koumenis, C: The adenovirus E4orf6 protein inhibits DNA double strand break repair and radiosensitizes human tumor cells in an E1B-55K-independent manner. J. Biol. Chem. 280:1474-1481, 2005.