Glucose dissociates DDX21 dimers to regulate mRNA processing and promote epidermal differentiation (CLIP-Seq)

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. Three biological replicates of primary human foreskin keratinocytes were used to identify DDX21-bound RNAs by CLIP-seq (easyCLIP variant) in differentiating cells under normal or low glucose conditions. Cells were infected with lentivirus to express an HA-tagged DDX21 expression construct. CLIP-seq sequencing was performed on a HiSeq X Ten, PE150, with ~35 M reads for each sample.