Project description:RNA binding proteins (RBPs) tightly control mRNA abundance, stability and translation while mutations or altered expression of specific factors can drive malignancy1,2. However, the identity of the RBPs that govern cancer stem cell self-renewal remains poorly characterized. The MSI2 RBP is a central regulator of translation of the cancer stem cell program3-5,6. Here we report, through proteomics analysis of the MSI2 interacting RBP network and functional shRNA screening, 24 genes required for in vivo leukemia, 20 of which are direct MSI2 protein interactors. Seven of these shRNA screen hits were retested in vitro and found to be required for myeloid colony formation. SYNCRIP (also known as HNRP-Q or NSAP1) was the most differentially required gene between normal (c-kit enriched cells) and myeloid leukemia cells. SYNCRIP is highly expressed in mouse and human leukemia cells and its depletion increases apoptosis, differentiation and delays leukemogenesis. Gene expression profiling of SYNCRIP depleted cells demonstrates a loss of the MLL-AF9 and HOXA9 leukemia stem cell gene associated program. SYNCRIP interacts with MSI2 indirectly through shared mRNA targets (such as Hoxa9, Myc and Ikzf2) and MSI2 or HOXA9 overexpression rescues the effects of SYNCRIP depletion. Strikingly, the shRNA-SYNCRIP gene expression signature can predict survival in AML patients. Overall, we uncovered a functionally dysregulated riboproteome in cancer that can be further distinguished from normal cells and propose that targeting this network could result in a novel therapeutic strategy in eradicating cancer stem cells.
Project description:How to respond to starvation determines fitness. One prominent behavioral response is increased locomotor activities upon starvation, also known as Starvation-Induced Hyperactivity (SIH). SIH is paradoxical as it promotes food seeking but also increases energy expenditure. Despite its importance in fitness, the genetic contributions to SIH as a behavioral trait remains unexplored. Here, we examined SIH in the Drosophila melanogaster Genetic Reference Panel (DGRP) and performed genome-wide association studies. We identified 23 significant loci, corresponding to 14 genes, significantly associated with SIH in adult Drosophila. Gene enrichment analyses indicated that genes encoding ion channels and mRNA binding proteins (RBPs) were most enriched in SIH. We are especially interested in RBPs because they provide a potential mechanism to quickly change protein expression in response to environmental challenges. Using RNA interference, we validated the role of syp in regulating SIH. syp encodes Syncrip (Syp), an RBP. While ubiquitous knockdown of syp led to semi-lethality in adult flies, adult flies with neuron-specific syp knockdown were viable and exhibited decreased SIH. Using the Temporal and Regional Gene Expression Targeting (TARGET) system, we further confirmed the role of Syp in adult neurons in regulating SIH. To determine how syp is regulated by starvation, we performed RNA-seq using the heads of flies maintained under either food or starvation conditions. RNA-seq analyses revealed that syp was alternatively spliced under starvation while its expression level was unchanged. We further generated an alternatively-spliced-exon-specific knockout (KO) line and found that KO flies showed reduced SIH. Together, this study demonstrates a significant genetic contribution to SIH as a behavioral trait, identifies syp as a SIH gene, and highlights the significance of RBPs and post-transcriptional processes in the brain in regulating behavioral responses to starvation.