Figure 4.

Accumulation of SULTR2, SLT1, and SLT2 transcripts and proteins and their decay following the addition of SO₄²⁻ to S-deprived cells. Time course of accumulation of SULTR2, SLT1, and SLT2 mRNAs (A) and polypeptides (B) upon transfer of cells from S-replete to TAP−S medium is shown. After 24 h in TAP−S, 1 mm MgSO₄ was added to starved culture. Samples were taken at 1, 2, 4, 8, 24, and 32 h after the starvation (from +S to −S) and 1, 2, 4, and 8 h after the addition of SO₄²⁻ back to cultures that had been S starved for 24 h. RNA and protein isolations are described in “Materials and Methods.” A ferroxidase, FOX1, served as a loading control (accumulation of FOX1 is S independent).