FIGURE 6.

ER stress response in str4Δ in the presence of homocysteine and its precursors. A, unfolded protein response in str4Δ cells. Cells were transformed with a plasmid (pJC005), a 2-μm plasmid carrying the lacZ gene under the control of the UPRE from the KAR2 promoter. Transformed cells were grown in respective conditions; cells were harvested at 16 h, and β-galactosidase activity was measured using 2-nitrophenyl-β-d-galactopyranoside as a substrate and detected as an increase in absorbance at 420 nm. B, expression of KAR2 gene determined by Northern blotting. The cells were grown in the presence and absence of homocysteine and its precursors for 16 h, and RNA was isolated from these cells. 20 μg of RNA was loaded per lane for Northern blot analysis. The lower panels in each blot represent gel loading of total RNA. Image was acquired using PhosphorImager and quantified by ImageQuant software. SAM, AdoMet; SAH, AdoHcy.