Figure 1: NEDD4 ubiquitinates H3 upon glucose stimulation.

(a) Summary of H3 ubiquitination sites identified in various large-scale quantitative proteomics studies. (b) Glucose deprivation abolished H3 ubiquitination. 293T cells were transfected with his-ubiquitin plasmid (His-Ub) for 36 h and treated with various stresses for 4 h before in vivo ubiquitination assay to access the H3 ubiquitination (see experimental procedures for details). (c) Add-back of glucose recovered H3 ubiquitination. 293T cells were transfected with his-ubiquitin plasmid for 36 h, then glucose-starved for 4 h and added-back glucose for indicated times (see experimental procedures for detail) before in vivo ubiquitination assay. (d) Screening of E3 ligases for H3 ubiquitination. 293T cells were transfected with his-ubiquitin plasmid and various E3 ligases constructs for in vivo ubiquitination assay. (e) NEDD4 E3 ligase dead mutant (CS mutant) failed to trigger H3 ubiquitination. 293T cells were transfected with his-ubiquitin plasmid and WT NEDD4 or NEDD4 CS mutant construct for in vivo ubiquitination assay. (f) NEDD4 knockdown abolished H3 ubiquitination. Control and NEDD4 knockdown 293T cells were transfected with his-ubiquitin plasmid for in vivo ubiquitination assay. (g) NEDD4 ubiquitinated H3 in vitro. In vitro ubiquitination assay was performed for recombinant NEDD4 and histone octamer (see experimental procedures for details). Reaction products were then assessed by western blotting using anti H3 antibody. H3 mono- and di-ubiquitination have predicted molecular weights of ∼25 kDa and ∼33 kDa. S.E. and L.E. are abbreviations for shorter exposure time and longer exposure time, respectively. (h) NEDD4 knockdown abolished glucose-induced H3 ubiquitination. Hep3B cells were glucose starved for 4 h and added-back glucose for 2 h before immunoprecipitation assay for endogenous ubiquitinated proteins (see experimental procedures for details). H3 ubiquitination was then visualized by western blotting. (i) Add-back of glucose recovered NEDD4 overexpression induced H3 ubiquitination. 293T cells were transfected with his-ubiquitin and NEDD4 plasmids for 36 h, then glucose-starved for 4 h and added-back glucose for indicated times before in vivo ubiquitination assay. (j) NEDD4 triggered monoubiquitination on H3. 293T cells were transfected with Flag-H3, HA-NEDD4, His-Ub WT and His-Ub K0 as indicated before in vivo ubiquitination assay. (k) Glucose-induced NEDD4 phosphorylation at Y43 and Y585. 293T cells transfected with WT or Y43/585F NEDD4 plasmids were treated with glucose and harvested for IP. (l) NEDD4 phosphorylation is required for H3 ubiquitination. 293T cells transfected with WT, Y43585F or Y43/585E NEDD4 plasmids were harvested for in vivo ubiquitination assay.