Human ERG Oncoprotein Represses Chip/LDB1 LIM-Domain Binding Gene in Drosophila

AbstractERG oncoprotein, a master transcription factor, targets diverse arrays of genes in different cancers. Identifying oncogenically relevant ones from these ERG targets, however, is challenging. Here we show that heterologous ERG disrupts a LIM-homeodomain (LIM-HD) complex, Chip-Tailup, in Drosophila. In the posterior thorax (notum) primordium, ERG-induced upregulation of E(z)/EZH2 trimethylates histones in Chip promoter. A consequent loss of the Chip-Tailup complex releases repression of N-Wg signaling in the notum, inducing de novo wings and, alternatively, carcinogenesis of ERG-expressing notal cells displaying loss of Lgl tumor suppressor. ERG-induced developmental or oncogenic fallouts are abrogated upon gain of Chip, N, or E(z) loss, besides Wg ligand sequestration. ERG-positive prostate cancer (PCa) cells, too, display suppression of mammalian homolog of Drosophila Chip, LIM Domain Binding1, LDB1. Deep homology in gene regulatory networks, like that of Chip-Tup complex, thus help prioritize identification of functionally relevant targets of human oncoproteins in Drosophila.HighlightsHuman ERG suppresses Chip, a LIM-domain binding, LDB gene in Drosophila via E(z)ERG-mediated Chip loss induces ectopic Wg morphogen signaling in the notum primordiumChip gain suppresses ERG-induced Wg morphogen and tumor progression in lgl clonesERG-positive human PCa cell lines show downregulation of a Chip homolog, LDB1In briefMammalian ERG oncoprotein displays a diverse and perplexing range of targets in different cancers. By driving ERG in Drosophila developing appendages, Bharti et al. reveal its repression of a LIM-domain coding gene, Chip/LDB1. ERG-positive prostate cancer cells, too, display Chip/LDB1 repression. Deep homology across phylogeny thus helps uncover oncoprotein targets.