Cytosine unstacking and strand slippage at an insertion-deletion mutation sequence in an overhang-containing DNA duplex.
Base unstacking in template strands, when accompanied by strand slippage, can result in deletion mutations during strand extension by nucleic acid polymerases. In a GCCC mutation hot-spot sequence, which was previously identified to have a 50% probability of causing such mutations during DNA replication by a Y-family polymerase, a single-base deletion mutation could result from such unstacking of any one of its three template cytosines. In this study, the intrinsic energetic differences in unstacking among these three cytosines in a solvated DNA duplex overhang model were examined using umbrella sampling molecular dynamics simulations. The free energy profiles obtained show that cytosine unstacking grows progressively more unfavorable as one moves inside the duplex from the 5'-end of the overhang template strand. Spontaneous strand slippage occurs in response to such base unstacking in the direction of both the major and minor grooves for all three cytosines. Unrestrained simulations run from three distinct strand-slipped states and one non-strand-slipped state suggest that a more duplexlike environment can help stabilize strand slippage. The possible underlying reasons and biological implications of these observations are discussed in the context of nucleic acid replication active site dynamics.
Laboratory of Computational and Structural Biology, Division of Genetics, Biggs Laboratory, Wadsworth Center, New York State Department of Health , Empire State Plaza, PO Box 509 , Albany, New York 12201-0509, United States.
Swati R
SR
Manjari
Janice D
JD
Pata
Nilesh K
NK
Banavali
D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003596:Cytosine / Q000737:chemistry* / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004261:DNA Replication; D043243:DNA Sequence, Unstable; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009010:Monte Carlo Method; D016254:Mutagenesis, Insertional; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009690:Nucleic Acid Conformation; D016945:Sulfolobus acidocaldarius / Q000201:enzymology
D019843:Archaeal Proteins; D050505:Mutant Proteins; D003596:Cytosine; D004247:DNA; D004259:DNA-Directed DNA Polymerase