Glucose dissociates DDX21 dimers to regulate mRNA processing and promote epidermal differentiation (CUT&RUN)

Glucose is an important cellular energy source, however, glucose's function as a second messenger remains relatively unexplored. Here, we find that glucose binds directly to DDX21 to regulate its function during epidermal differentiation. Specifically, glucose binds to the ATP-binding domain of DDX21 to induce a conformational change and inhibit helicase activity. Glucose binding inhibits the dimerization of DDX21 leading to re-localization from the nucleolus to the nucleoplasm and reassembly of DDX21 into larger protein complexes, increasing its association with splicing factors. This occurs during keratinocyte differentiation, where glucose accumulation is necessary, and results in DDX21 binding to RNA processing proteins and mRNA introns. Consequently, DDX21 regulates the splicing of key differentiation factors and promotes epidermal differentiation in a glucose-dependent manner. These findings reveal a novel mechanism of glucose regulation of cell signaling. Overall design: CUT&RUN was performed on primary human keratinocytes from 4 unrelated donors using HA-tagged DDX21 (anti-HA, CST, #3724) and one donor was assayed with antibodies to endogenous DDX21 (ProteinTech, 10528-1-AP) in place of HA-DDX21. H3K27me3 and IgG controls were performed on the same donor tissue (antibodies: IgG, CST, #2729; anti-H3K27me3, Active Motif, 39055).