PARENT SESSION
1:30 PM to 3:30 PM
Wednesday, April 24, 2002
Poster Session 35 Other
Room: Nevada Exhibition Center
(P39-371) Generation of Genomic Instability by Formation of Breakage-Prone Chromosomal Rearrangement Junction Sequences.
Allen, Rebecca*,1, Moore, Stephen1, Grosovsky, Andrew1, 1 Department of Cell Biology and Neuroscience, 5419 Boyce Hall, Unversity of California, Riverside, CA
ABSTRACT-
Previous studies in our lab have led to the hypothesis that chromosomal rearrangements can generate novel breakage-prone sites, resulting in chromosomal instability acting predominantly in cis. Several lines of evidence support this hypothesis. For example, genomic instability can be efficiently induced by specific breakage of large blocks of centromeric region heterochromatin on chromosome 16q by treatment with 2,6-diaminopurine (DAP). Chromosome 16q was then repeatedly broken and rearranged during outgrowth of DAP-treated clones, thereby establishing a link between the initial site of damage and the occurrence of persistent chromosomal instability. Similar results have been observed with gamma-ray induced instability; sub-clonal analysis demonstrated that delayed chromosomal rearrangements were significantly clustered near the site of previously identified chromosomal rearrangement junctions in unstable parental clones. This study investigates the hypothesis that integration of transfected sequences into host chromosomes could create breakage-prone junction regions and persistent genomic instability without exposure to DNA-damage agents. These junctions would mimic some of the unstable chromosomal rearrangements induced by DAP or radiation, and thus provide a test of the broader hypothesis that instability can to some extent be attributed to the formation of novel chromosomal breakage hot spots. These experiments were performed using human-hamster hybrid AL cells containing a single human chromosome 11, which was used to monitor instability in a chromosomal painting assay. Initial experiments were performed by transfection with alpha heterochromatin DNA, which resulted in chromosomal instability in 36% of the transfected clones. Parallel exposure to gamma-radiation resulted in a similar level and type of chromosomal instability, although control transfections with plasmid alone did not lead to karyotypic instability. Heterochromatic sequences in mammalian genomes represent approximately 9% of the total DNA, and are frequently associated with chromosomal rearrangement breakpoints. Therefore, this mechanism could potentially account for a significant fraction of induced genomic instability.
KEYWORDS: instability, heterochromatin