Project description:Alveolar rhabdomyosarcoma (aRMS) is an aggressive sarcoma of skeletal muscle characterized by expression of the PAX3-FOXO1 fusion gene. Despite its discovery over almost 20 years ago, PAX3-FOXO1 remains an enigmatic tumor driver. Previously, we reported that PAX3-FOXO1 supports aRMS initiation by enabling bypass of cellular senescence. Here, we show that bypass occurs in part by PAX3-FOXO1-mediated upregulation of RASSF4, a Ras-association domain family (RASSF) member, which then suppresses the evolutionarily conserved mammalian Hippo/Mst1 pathway. RASSF4 loss-of-function activates Hippo/Mst1 and inhibits downstream YAP, causing aRMS cell cycle arrest and senescence. This is the first evidence for an oncogenic role for RASSF4, and a novel mechanism for Hippo signaling suppression in human cancer. Human skeletal muscle myoblasts (HSMMs) were retrovirally transduced with either an empty vector (Vp, pK1) or PAX3-FOXO1 (PFp, pK1-PAX3-FOXO1) and selected on puromycin. Presenescent (presen) cells were harvested before the senescence checkpoint. Since cells expressing PAX3-FOXO1 can bypass the senescence checkpoint, postsenescent (postsen) cells expressing PAX3-FOXO1 were also harvested. the gene expression affected by the introduction of PAX3-FOXO1
Project description:Alveolar rhabdomyosarcoma (aRMS) is an aggressive sarcoma of skeletal muscle characterized by expression of the PAX3-FOXO1 fusion gene. Despite its discovery over almost 20 years ago, PAX3-FOXO1 remains an enigmatic tumor driver. Previously, we reported that PAX3-FOXO1 supports aRMS initiation by enabling bypass of cellular senescence. Here, we show that bypass occurs in part by PAX3-FOXO1-mediated upregulation of RASSF4, a Ras-association domain family (RASSF) member, which then suppresses the evolutionarily conserved mammalian Hippo/Mst1 pathway. RASSF4 loss-of-function activates Hippo/Mst1 and inhibits downstream YAP, causing aRMS cell cycle arrest and senescence. This is the first evidence for an oncogenic role for RASSF4, and a novel mechanism for Hippo signaling suppression in human cancer. Human skeletal muscle myoblasts (HSMMs) were retrovirally transduced with either an empty vector (Vp, pK1) or PAX3-FOXO1 (PFp, pK1-PAX3-FOXO1) and selected on puromycin. Presenescent (presen) cells were harvested before the senescence checkpoint. Since cells expressing PAX3-FOXO1 can bypass the senescence checkpoint, postsenescent (postsen) cells expressing PAX3-FOXO1 were also harvested.
Project description:Splicing dysregulations extensively occur in cancers, yet the biological consequences of such alterations are mostly undefined. Here we report that the Hippo-YAP signaling, a key pathway that regulates cell proliferation and organ size, is under control of a new splicing switch. We show that TEAD4, the transcription factor that mediates Hippo-YAP signaling, undergoes alternative splicing facilitated by the tumor suppressor RBM4, producing a truncated isoform, TEAD4-S, which lacks N-terminal DNA-binding domain but maintains YAP-interaction domain. TEAD4-S is located in both nucleus and cytoplasm, acting as a dominant negative isoform to YAP activity. Consistently, TEAD4-S is reduced in cancer cells, and its re-expression suppresses cancer cell proliferation and migration, inhibiting tumor growth in xenograft mouse model. Furthermore, TEAD4-S is reduced in human cancers, and patients with elevated TEAD4-S levels have improved survival. Altogether these data reveal a novel RBM4-mediated splicing switch that serves to fine-tune Hippo-YAP pathway. Cell lines stably expressing YAP, YAP/TEAD4-S, YAP/TEAD4-FL, YAP/RBM4 and control vector were created, and the total RNA was purified from the cells using TRIzol reagents. The polyadenylated RNAs were purified for construction of sequencing library using kapa TruSeq Total RNA Sample Prep kits (UNC High Throughput Sequencing Facility).
Project description:As a classic tumor suppressor pathway, Hippo signaling axis is activated by various extra-pathway factors to regulate cell differentiation and organ development. However, recent studies have reported that the activation of Hippo signaling pathway may be more dependent on the autophosphorylation of its core kinase cassette. Here, we demonstrate that protein arginine methyltransferase 5 (PRMT5) is involved in inducing the inactivation of Hippo signaling pathway in pancreatic cancer. Our study shows that the initiator serine/threonine kinase 3 (STK3, also known as MST2) of Hippo signaling pathway can be symmetrically di-methylated at arginine-461 (R461) and arginine-467 (R467) in the SARAH domain by PRMT5, and the methylated MST2 suppresses its autophosphorylation and kinase activity by blocking the formation of homodimer, thereby inactivating Hippo signaling pathway in pancreatic cancer. Moreover, we also discover that the specific PRMT5 inhibitor GSK3326595 re-activates the dysregulated Hippo signaling pathway and inhibits the growth of human-derived pancreatic cancer xenografts in immunodeficient mice, which provides a theoretical foundation for the clinical application of PRMT5 inhibitor in pancreatic cancer.
Project description:The sinoatrial node (SAN) functions as pacemaker of the heart to initiate and drive rhythmic heartbeats. The Hippo signaling pathway is a fundamental pathway for heart development and regeneration. Although abnormalities of Hippo pathway are associated with cardiac arrhythmias in human patients, yet its role in the SAN is unknown. We found that Lats1/2 inactivation caused severe sinoatrial node dysfunction (SND; sick sinus syndrome). Compared to the controls, Lats1/2 CKO mutants exhibited dysregulated calcium handling and increased fibrosis in the sinoatrial node, indicating Lats1/2 function through both cell-autonomous and non-cell-autonomous mechanisms. Notably, the Lats1/2 CKO phenotype was rescued by genetic deletion of Yap and Taz in the CCS, and these rescued mice had normal sinus rhythm and reduced fibrosis of the sinoatrial node, indicating that Lats1/2 function through Yap and Taz. CUT&Tag sequencing data showed that Yap regulates genes critical for calcium homeostasis such as Ryr2 and genes encoding paracrine factors important in intercellular communication and fibrosis induction such as Tgf-β1 and Tgf-β3. Consistently, Lats1/2 CKO mutants had decreased Ryr2 expression and increased Tgf-β1 and Tgf-β3 expression compared with control mice. We reveal for the first time that the canonical Hippo-Yap pathway has a pivotal role in functional homeostasis of the sinoatrial node.
Project description:The Hippo pathway, which is conserved from Drosophila to mammals, has been recognized as a tumor suppressor signaling pathway governing cell proliferation and apoptosis, two key events involved in organ size control and tumorigenesis. Although several upstream regulators, the conserved kinase cascade and key downstream effectors including nuclear transcriptional factors have been defined, the global organization of this signaling pathway is not been fully understood. Thus, we conducted a proteomic analysis of human Hippo pathway, which revealed the involvement of an extensive protein-protein interaction network in this pathway. Our data suggest that 550 interactions within 343 unique protein components constitute the central protein-protein interaction landscape of human Hippo pathway. Our study provides a glimpse into the global organization of Hippo pathway, reveals previously unknown interactions within this pathway, and uncovers new potential components involved in the regulation of this pathway. Understanding these interactions will help us further dissect the Hippo signaling-pathway and extend our knowledge of organ size control. Mass spectrometry data anaylsis: Excised gel bands were cut into approximately 1 mm3 pieces. Gel pieces were then subjected to in-gel trypsin digestion and dried. Samples were reconstituted in 5 ul of HPLC solvent A (2.5% acetonitrile, 0.1% formic acid). A nano-scale reverse-phase HPLC capillary column was created by packing 5 um C18 spherical silica beads into a fused silica capillary (100 um inner diameter x 20 cm length) with a flame-drawn tip. After equilibrating the column each sample was loaded via a Famos autosampler (LC Packings, San Francisco CA) onto the column. A gradient was formed and peptides were eluted with increasing concentrations of solvent B (97.5% acetonitrile, 0.1% formic acid). As peptides eluted they were subjected to electrospray ionization and then entered into an LTQ Velos ion-trap mass spectrometer (ThermoFisher, San Jose, CA). Peptides were detected, isolated, and fragmented to produce a tandem mass spectrum of specific fragment ions for each peptide. Peptide sequences (and hence protein identity) were determined by matching protein databases with the acquired fragmentation pattern by the software program, SEQUEST (ver. 28). (ThermoFisher, San Jose, CA). Enzyme specificity was set to partially tryptic with 2 missed cleavages. Modifications included carboxyamidomethyl (cysteines, fixed) and oxidation (methionine, variable). Mass tolerance was set to 2.0 for precursor ions and 1.0 for fragment ions. The database searched was the Human IPI databases version 3.6. Because we used HEK293 cells the Human IPI database was used. The number of entries in the database was 160,900 which included both the target (forward) and the decoy (reversed) human sequences. Spectral matches were filtered to contain less than 1% FDR at the peptide level based on the target-decoy method. Finally, only tryptic matches were reported and spectral matches were manually examined. When peptides matched to multiple proteins, the peptide was assigned so that only the most logical protein was included (Occam's razor). This same principle was used for isoforms when present in the database.