Figure 5.

Gene body H3K36me3 level is negatively correlated with age-dependent mRNA expression change in Drosophila heads. (A) All genes with mappable H3K36me3 ChIP–chip and RNA-seq reads are plotted in the order of normalized H3K36me3 levels at the young time point from low (left) to high (right) (shown in red). The corresponding log₂ values of age-dependent fold change in mRNA abundance are plotted in black. (ρ) Spearman's correlation coefficient between absolute log₂ values of fold change in mRNA abundance and log₂ values of normalized H3K36me3. (***) P-value < 0.001. (B) Genes plotted in A were divided into 10 bins of equal number of genes (except bin 10, which had extra transcripts) according to their normalized H3K36me3 levels from low (left) to high (right). Variance of the age-dependent mRNA abundance change for each bin is shown. (C) Regression plot showing log₂ of the variance in mRNA abundance change from B as a function of median H3K36me3 level. (D) The negative correlation between H3K36me3 level and gene expression change is independent of mRNA abundance. (Middle panel) Genes plotted in A were divided into three groups (low, medium, and high) according to mRNA abundance. Genes in each subgroup were plotted in the order of normalized H3K36me3 levels at the young time point from low (left) to high (right) (shown in red). (Top panel) The corresponding log₂ values of age-dependent fold change in mRNA abundance are plotted in black. Genes in each subgroup (low, medium, and high) were divided into five bins of equal numbers of genes (except bin 5, which had extra genes) according to their normalized H3K36me3 level from low (L) to high (H). (Bottom panel) The variance of age-dependent mRNA abundance change for each bin is shown. (ρ) Spearman's correlation coefficient between absolute log₂ values of fold change in mRNA abundance and log₂ values of normalized H3K36me3. (***) P-value < 0.001.