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In Saccharomyces cerevisiae, telomeres repress transcription of genes located nearby. This region-specific gene inactivation is thought to involve the packaging of telomeric domains into silent chromatin. To gain insight into the mechanism of telomeric silencing, a genetic assay to examine the spread of silencing along the distal right arm of chromosome V was developed. The frequency of silencing a telomere-adjacent URA3 gene decreased with increasing distance of the gene's promoter from the telomere, irrespective of transcriptional orientation. The distance over which telomeric silencing of URA3 was observed was extended by weakening the gene's promotermspecifically, by deleting PPR1, the trans-activator of URA3. The silent telomeric domain was extended even farther by increasing the gene dosage of SIR3. These results suggest that a gene's promoter is a key determinant in controlling silencing on that gene and that SIR3 is a crucial component of the silent chromatin domain that initiates at the telomere and is assembled inwardly along the yeast chromosome. Finally, silencing is not observed on the centromeric side of an actively transcribed telomeric gene, demonstrating that the repressed telomeric domain is propagated continuously along the DNA. Taken together, these data reflect the complex and dynamic organization of eukaryotic genomes into functionally distinct regions.

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This article addresses economically disadvantaged minority girls' knowledge and perceptions of science and engineering and the influence of their experiences with science, technology, engineering, and mathematics (STEM) on their choices for future careers. We interviewed three girls who participated in a 4-H–led gender-inclusive STEM program. Our findings suggest that the girls lacked opportunities to learn STEM in out-of-school settings and that they had very limited knowledge about STEM professions. They did not associate their job aspirations as being related to STEM, even though they were. To better prepare such girls to engage in STEM, educators need to provide long-term interventions that are supported by both out-of-school programs and families.