MeCP2 Interacts with the Super Elongation Complex to Regulate Transcription (RNA-Seq)

Loss-of-function mutations in methyl-CpG binding protein 2 (MECP2) cause the neurodevelopmental disorder, Rett syndrome (RTT). The molecular mechanisms underlying MeCP2 function remain poorly understood. Here, using a MECP2 gain-of-function Drosophila model, we screened for genetic modifiers of MECP2-induced toxicity. Our approach identified several subunits of the Drosophila super elongation complex (SEC), a P-TEFb containing elongation factor that releases promoter-proximally paused RNA polymerase II (RNA pol II), as genetic interactors of MECP2. MeCP2 directly interacts with AFF4, the scaffold of the SEC, and facilitates its binding on a subset of genes that regulate neuronal development and synaptic function in the mouse cortex. Furthermore, genes with reduced AFF4 binding showed reduced RNA pol II binding in their genebody and decreased RNA expression in Mecp2 null mice. Taken together, we propose that MeCP2 interacts with the SEC to facilitate the release of RNA pol II and thereby support gene expression.