Table III. Effects on transcriptional silencing in SIR2 and sir2Δ strains.
| Genotype |
SIR2 |
sir2Δ |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Locus monitored |
TelVIIL::URA3 |
TelVR::ADE2 |
RDN1::mURA3 |
HMLα |
TelVR::ADE2 |
RDN1::mURA3 |
|||||
| Media | Glu | Gal | Glu | Gal | Glu | Gal | Glu | Gal | Glu | Gal | |
| Protein expressed | |||||||||||
| none (vector) | wt | wt | sectored | sectored | wt | wt | – | – | – | – | – |
| ySir2 | ++ | – | red | white/pink | + | ++ | + | + | – | + | + |
| ysir2LGG | – | — | white | white | – | – | – | – | – | – | – |
| ysir2P394L | – | — | white | white | wt | wt | + | – | – | – | – |
| yHst2 | wt | (–/+)a | sectored | white | wt | ++ | – | – | – | – | – |
| NLS–Hst2 | wt | (–/+)a | sectored | white | wt | ++ | – | – | – | – | – |
| yHst1 | – | – | white/pink | white/pink | nd | nd | nd | nd | nd | nd | nd |
| hSirT2 | wt | wt | sectored | sectored | wt | wt | nd | – | – | – | – |
| hSirT2P182L | wt | wt | sectored | sectored | wt | wt | nd | – | – | – | – |
Telomeric silencing was assayed in GA424 (SIR2, TelVIIL::URA3), GA503 (SIR2, TelVIIL::URA3, TelVR::ADE2), GA426 (SIR2, TelVR::ADE2)and GA427 (sir2::HIS3, TelVR::ADE2), while rDNA repression was measured in GA758 (SIR2, RDN1::mURA3) and GA759 (sir2::kanMX4, RDN1::mURA3). Wt, for wild-type levels of silencing based on Sir2+ strains transformed with the empty vector; +, repression better than wt; –, repression less than wt; —, a very pronounced reduction of silencing; (–/+), derepression that is coupled with slow growth and reduced viability.
aCells of GA503 and GA424, which overexpress either yHst2p or NLS–yHst2p, grow ∼10 times less efficiently, possibly due to a negative effect of yHst2p on pathways required for growth on galactose. This effect is less pronounced in GA758 in which we test rDNA silencing.