A helicase-independent role of DHX15 promotes MYC stability and acute leukemia cell survival
DHX15 has been implicated in RNA splicing and ribosome biogenesis, primarily functioning as an RNA helicase. To systematically assess the cellular role of DHX15, we conducted proteomic analysis to investigate the landscape of DHX15 interactome, and identified MYC as a binding partner. DHX15 co-localizes with MYC in cells and directly interacts with MYC in vitro. Importantly, DHX15 contributes to MYC protein stability at the post-translational level and independent of its RNA binding capacity. Mechanistic investigation reveals that DHX15 interferes the interaction between MYC and FBXW7, thereby preventing MYC polyubiquitylation and proteasomal degradation. Consequently, abrogation of DHX15 drastically inhibits MYC-mediated transcriptional output. While DHX15 depletion blocks T-cell development and leukemia cell survival as we recently reported, overexpression of MYC significantly rescues the phenotypic defects. These findings shed light on the essential role of DHX15 in mammalian cells and suggest that maintaining sufficient MYC expression is a significant contributor to DHX15-mediated cellular functions. Overall design: To confirm the pivotal role of MYC as a significant downstream target of DHX15, we performed the transcriptome analysis in DHX15-depleted KOPTK1 cells while MYC was restored.