TABLE 4.
Effects of rnc+ and rnc-70 mutation on Nun-dependent termination in vivoa
| Strain | Presence of sequence
|
β-Galactosidase activity (Miller units) | % Readthrough | ||
|---|---|---|---|---|---|
| rIII | nun | rnc | |||
| N9478 | + | − | − | 2,420 ± 480 | 100 |
| N9480 | + | + | − | 30 ± 2 | 1.2 |
| N9484 | + | + | WT | 18 ± 2 | 0.8 |
| N9485 | + | + | Rnc70 | 560 ± 38 | 23 |
| N9479 | − | − | − | 2,040 ± 200 | 100 |
| N9481 | − | + | − | 27 ± 14 | 1.4 |
| N9486 | − | + | WT | 15 ± 1 | 0.8 |
| N9487 | − | + | Rnc70 | 96 ± 5 | 4.8 |
a
All strains carry either pL-nutL-rIII-N-lacZ (rIII+) or pL-nutL-ΔrIII-N-lacZ (rIII mutant) under the control of the λ cI857 ts repressor. Nun, when present, was provided by an HK022 lysogen. The rnc indicates the presence of either a wild type (WT)- or mutant (Rnc70)-overproducing rnc plasmid. Strains were grown at 32°C to mid-log phase, shifted to 42°C for 1.5 h to induce pL, and assayed for β-galactosidase activity. Nun termination/arrest is indicated by the β-galactosidase level. Values are given in Miller units and represent the averages ± standard deviations for three or more experiments.