Book of Abstracts: Albany 2009
June 16-20 2009
© Adenine Press (2008)
DNA Structure-induced Genetic Instability
Naturally occurring DNA repeat sequences can form non-canonical DNA structures such as H-DNA and Z-DNA, which are abundant in mammalian genomes. Here we show that both H-DNA and Z-DNA structures are intrinsically mutagenic in mammalian cells. We found that the endogenous H-DNA-forming sequence in the human c-MYC promoter induced mutation frequencies ~20-fold over background, largely in the form of double-strand breaks (DSBs). In mammalian cells, Z-DNA-forming CG(14) repeats also lead to DSBs, resulting in deletions. We found that the non-B DNA-induced deletions were, in part, replication-independent, and were likely initiated by ?repair processing? cleavages surrounding the non-B-DNA structures (Wang & Vasquez, PNAS, 2004; Wang et al., PNAS, 2006). We are performing studies to determine the role of repair enzymes in H-DNA and Z-DNA-induced genetic instability in mammalian cells. Our findings suggest that both H-DNA and Z-DNA, which have been reported to correlate with chromosomal breakpoints in human tumors, are sources of genetic instability, and demonstrate that naturally occurring DNA sequences are mutagenic in mammalian cells and may contribute to evolution and disease. We have constructed novel transgenic mutation-reporter mice containing the H-DNA sequence from the human c-MYC promoter, or a Z-DNA-forming sequence from the human BCL-2 gene, both of which map to chromosomal breakpoints in human cancers (Wang et al., JNCI, 2008). We have detected genetic instability induced by these DNA structures in ~20% of the offspring, suggesting that these structures are mutagenic in a chromosomal context in a living organism.
Department of Carcinogenesis