FIG. 4.
Hmo1 is a nonessential activator of RP gene expression. (A) Ifh1 depletion is lethal in the absence of Hmo1. IFH1 was placed under the control of a tetracycline-regulatable promoter (Ptet-IFH1). Growth was scored without (0 μg/ml), with mild (2.5 μg/ml), or with strong (20 μg/ml) repression of IFH1 transcription. Ifh1 depletion was performed in wild-type (+; YAB103-1a), hmo1Δ (YAB103-1a cured of pRS316-HMO1), and fpr1Δ (YAB106-1a cured of pRS316-FPR1) strains. Tenfold serial dilution series were spotted on rich medium in the presence of increasing concentrations of doxycycline. Growth was observed after 5 days of incubation at 30°C. (B) Transcriptome analysis of hmo1 deletion and of Hmo1 depletion. Total RNA was extracted and reverse transcribed from a wild-type strain (BY4741) or from an hmo1-Δ strain (Y06969). Depletion of Hmo1 (Hmo1-depleted) was performed for 6 h by adding 5 μg/ml doxycycline to YAB108-1a; untreated cells were used as a control (WT). The histograms represent the percentages of total transcript (black) and RP gene mRNAs (gray) with given variations compared to the wild-type levels (x axis).