Fig. 6.

Serum depletion following corticosterone incubation attenuates retrotransposon expression and increases H3K9me3 occupancy at retrotransposon loci.

C6 cells were incubated with either 100 μM CORT or vehicle serum augmented media for 1 h then media for both conditions was changed with serum-depleted DMEM. After 1 h in serum-depleted media, cells were harvested for RNA extraction. As shown above, IAP-ERV (Fig. 6A) and B2 SINE (Fig. 6B) expression is reduced to control levels following 1hr depletion. Increased H3K9me3 accumulation at RTs is observed after 1hr 100 μM CORT incubation followed by 1hr serum depletion. Percent input is shown for H3K9me3-ChIP followed by qPCR (mean ± SEM). H3K9me3 binding of IAP-ERV elements is significantly higher after 1hr 100 μM CORT incubation followed by 1hr serum depletion compared to control (Fig. 6C, student's t-test, n = 3 per group, p < 0.001). H3K9me3 binding of B2 elements is significantly higher after 1hr 100 μM CORT incubation followed by 1hr serum depletion compared to control (Fig. 6D, student's t-test, n = 3 per group, p < 0.0001). Increased H3K9me3 at RT after 1hr 100 μM CORT incubation followed by 1hr serum depletion is correlated with reduced RT expression, returning to control levels, suggesting that H3K9me3 silences RT expression following CORT depletion.