Programmed DNA Deletion As an RNA-Guided System of Genome Defense

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Science  06 Jun 2003:
Vol. 300, Issue 5625, pp. 1581-1584
DOI: 10.1126/science.1084737

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Genomewide DNA rearrangements occur in many eukaryotes during development, but their functions and mechanisms are poorly understood. Previous studies have implicated a sequence-recognition mechanism based on RNA-mediated interactions between nuclei in ciliated protozoa. In this study, we found that the process recognized and deleted a foreign gene integrated in a Tetrahymena chromosome, suggesting an unusual mechanism of genome surveillance. We further found that injection of double-stranded RNA into the cell at specific developmental stages triggers efficient deletion of the targeted genomic regions. Together the results indicate an RNA-based mechanism that directs genomewide DNA rearrangements and serves to disable invading genetic agents.

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