Figure 3.—

The sir2-276 mutation confers a complete silencing defect at telomeres and a temperature-sensitive silencing defect at rDNA. (A) Telomeric silencing. Fivefold serial dilutions of overnight cultures grown in YPD medium of SIR2 (CCF100) and sir2-276 strains (RS2350 and RS2351) containing a URA3 reporter gene integrated near telomere VR were spotted onto YPD plates and 5-FOA plates at either 25° or 37°. Good growth on 5-FOA plates means good silencing. (B) rDNA silencing. Strains RS2364 and RS2365, both with a sir2Δ mutation and containing a URA3 reporter gene within the rDNA, were transformed with a SIR2 plasmid, a plasmid expressing sir2-276, or vector. Transformed strains were grown overnight in SC −His −Leu medium at 25° or 37° and fivefold serial dilutions spotted on selective medium without and with 5-FOA.