Fig. 7.

DBC1-mediated ELL stabilization is required for expression of genes that are associated with glucose homeostasis in humans. (A) GO analysis showing the different types of metabolic processes controlled by DBC1-ELL coregulated genes that are predicted to be involved in controlling metabolic processes (24% as shown in SI Appendix, Fig. S6D). (B) GO analysis predicting the involvement of DBC1-ELL coregulated genes (SI Appendix, Fig. S6C) in various human diseases. (C) The qRT-PCR analysis showing the effect of DBC1 knockdown on the basal level expression of various glucose metabolism-related genes compared to control scramble knockdown cells. (D) ChIP analysis showing the recruitment of several target factors at the TSS region of GLUT1 gene upon knockdown of DBC1. (E) The qRT-PCR analysis showing the effect of reexpression of ELL in DBC1 knockdown cells on basal level expression of GLUT1 gene in 293T cells. (F) Quantitation of the level of indicated target proteins (DBC1, ELL, and HDAC3) in healthy and T2DM patient cohort samples (n = 30 for each) as measured by Western blot analysis. Actin was used as loading control for each sample. (G) The qRT-PCR analysis showing the expression of different target genes (at RNA level) in healthy and patient cohort samples (n = 25). For the ease of dealing with total number of samples for subsequent qRT-PCR analysis, equal concentrations of RNA sample from five individuals were pooled (in an unbiased way) and mixed together to form a group. A total of five groups each of healthy and patient RNA samples were tested for presence of target RNAs. (H) Cartoon diagram showing the overall model of the role of p300-mediated acetylation, DBC1-mediated acetylation protection, HDAC3-mediated deacetylation, and subsequent Siah1-mediated degradation in maintaining ELL level for proper expression of target genes that are strongly associated with glucose homeostasis in healthy individuals. A down-regulation of upstream DBC1 in these processes leads to decreased ELL level through HDAC3-mediated degradation and thus possibly leads to decreased expression of key genes required for glucose homeostasis in healthy individuals, thus indicating a possible involvement of this mechanism of hyperglycemia in Type 2 diabetes patients. In all of our statistical analyses, one-tailed Student’s t test was used to calculate the statistical significance of the data, wherein * denotes P ≤ 0.05, **denotes P ≤ 0.01, *** denotes P ≤ 0.001, and ns denotes not significant.