Figure 3. Quantitative Western blots measuring steady-state levels of K4-methylated histone H3 in cells expressing wild-type and mutant alleles of SET1.

Representative Western blotting experiments are shown for cells carrying wild-type SET1 at its endogenous location, set1Δ and set1 amino acid substitution alleles. Dilutions of protein extracts (µg loaded indicated below the lower panel) from wild-type (WT), set1Δ, and Set1 mutant cells were analyzed by Western blotting with specific antibodies to measure the in vivo steady-state levels of K4-monomethylated H3 (α-mono), K4-dimethylated H3 (α-di), and K4-trimethylated H3 (α-tri). The level of histone H3 (α-H3) or Pgk1 (α-Pgk1) protein was used to normalize the amount of protein loaded in each lane. The average level of normalized K4-methylated H3 detected in Set1 mutant extracts relative to wild-type extracts is shown below each blot (n = 2). See Table 1 for the normalized average +/− range for each mutant.