Duplications between direct repeats stabilized by DNA secondary structure occur preferentially in the leading strand during DNA replication.
To ascertain a leading or lagging strand preference for duplication mutations, several short DNA sequences, i.e. mutation inserts, were designed that should demonstrate an asymmetric propensity for duplication mutations in the two complementary DNA strands during replication. The design of the mutation insert involved a 7-bp quasi inverted repeat that forms a remarkably stable hairpin in one DNA strand, but not the other. The inverted repeat is asymmetrically placed between flanking direct repeats. This sequence was cloned into a modified chloramphenicol acetyltransferase (CAT) gene containing a -1 frameshift mutation. Duplication of the mutation insert restores the reading frame of the CAT gene resulting in a chloramphenicol resistant phenotype. The mutation insert showed greater than a 200-fold preference for duplication mutations during leading strand, compared with lagging strand, replication. This result suggests that misalignment stabilized by DNA secondary structure, leading to duplication between direct repeats, occurred preferentially during leading strand synthesis.
Hashem
Vera I
VI
Laboratory of DNA Structure and Mutagenesis, Center for Genome Research, Institute of Biosciences and Technology, Texas A&M University System Health Sciences Center, 2121 West Holcombe Blvd., Houston, TX 77030-3303, USA.
Sinden
Richard R
RR
D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D017931:DNA Primers; D004261:DNA Replication; D009690:Nucleic Acid Conformation; D016133:Polymerase Chain Reaction
D017931:DNA Primers; D004247:DNA