FIG. 1.

TNA1, TNR1, and TNR2 are transcriptionally induced by niacin limitation. (A) S1 nuclease analysis of TNA1, TNR1/TNR2, and ACT1 transcript levels. RNA prepared from strain BG2 growing in SC medium containing 3.25 μM or 16 nM NA or in three different urine samples. The OD₆₀₀ of all cultures was 0.5. (B) S1 nuclease analysis of TNA1 and TNR1/TNR2 transcript levels of the BG2, tnr1 mutant (BG1338), tnr2 mutant (BG1335), and tnr1 tnr2 mutant (BG1337) strains. Strains were grown in SC medium containing16 nM NA. The OD₆₀₀ of all cultures was 0.5. (C) S1 nuclease analysis of TNA1 and TNR1/TNR2 transcript levels of strain BG2 growing in SC medium with limiting amounts of niacin (SC-NA, 16 nM), thiamine (SC-Thi, 6 nM), or pyridoxine (SC-Pyr, 0.19 nM). At these vitamin levels, the terminal OD₆₀₀ of all of the cultures was 1.5.