Genetics

The Bases of Breakpoints

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Science  13 Dec 2002:
Vol. 298, Issue 5601, pp. 2093
DOI: 10.1126/science.298.5601.2093b

Microorganisms can restructure their genomes in response to environmental pressures. When glucose is scarce, budding yeast sequentially acquire mutations that enable “evolved” clones to assimilate glucose more rapidly than their ancestors. Further work has hinted that this capacity is enabled by gene amplification, but other mechanisms may come into play in other evolutionary contexts, such as speciation and tumor progression.

Dunham et al. used microarray-based comparative genomic hybridization (CGH) to screen nutritionally challenged yeast at single-gene resolution. They found that genome rearrangements occurred nonrandomly and were especially frequent near transposon-related sequences. Moreover, some of these rearrangements probably account for the observed increases in fitness. For example, three clones displayed an identical transposon-associated breakpoint adjacent to the gene encoding citrate synthase—the entry point into the tricarboxylic acid cycle—and three clones had amplifications in hexose transporters. Cha and Kleckner (Reports, 26 July, p. 602) have suggested that transposon sites are fragile in some way, and Dunham et al. contend that they provision yeast with adaptive resources and may relate to processes by which mammalian genomes evolve during tumorigenesis. — CA

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.242624799 (2002).

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