ABSTRACT
SUFU alterations are common in human Sonic Hedgehog (SHH) subgroup medulloblastoma (MB). However, its tumorigenic mechanisms have remained elusive. Here, we report that loss of Sufu alone is unable to induce MB formation in mice, due to insufficient Gli2 activation. Simultaneous loss of Spop, an E3 ubiquitin ligase targeting Gli2, restores robust Gli2 activation and induces rapid MB formation in Sufu knockout background. We also demonstrated a tumor-promoting role of Sufu in Smo-activated MB (â¼60% of human SHH MB) by maintaining robust Gli activity. Having established Gli2 activation as a key driver of SHH MB, we report a comprehensive analysis of its targetome. Furthermore, we identified Atoh1 as a target and molecular accomplice of Gli2 that activates core SHH MB signature genes in a synergistic manner. Overall, our work establishes the dual role of SUFU in SHH MB and provides mechanistic insights into transcriptional regulation underlying Gli2-mediated SHH MB tumorigenesis.
Subject(s)
Cell Transformation, Neoplastic/genetics , Nuclear Proteins/genetics , Repressor Proteins/genetics , Zinc Finger Protein Gli2/genetics , Animals , Hedgehog Proteins/genetics , Humans , Medulloblastoma/genetics , MiceABSTRACT
Pseudomonas syringae subverts plant immune signalling through injection of type III secreted effectors (T3SE) into host cells. The T3SE HopF2 can disable Arabidopsis immunity through Its ADP-ribosyltransferase activity. Proteomic analysis of HopF2 interacting proteins identified a protein complex containing ATPases required for regulating stomatal aperture, suggesting HopF2 may manipulate stomatal immunity. Here we report HopF2 can inhibit stomatal immunity independent of its ADP-ribosyltransferase activity. Transgenic expression of HopF2 in Arabidopsis inhibits stomatal closing in response to P. syringae and increases the virulence of surface inoculated P. syringae. Further, transgenic expression of HopF2 inhibits flg22 induced reactive oxygen species production. Intriguingly, ADP-ribosyltransferase activity is dispensable for inhibiting stomatal immunity and flg22 induced reactive oxygen species. Together, this implies HopF2 may be a bifunctional T3SE with ADP-ribosyltransferase activity required for inhibiting apoplastic immunity and an independent function required to inhibit stomatal immunity.
Subject(s)
ADP Ribose Transferases/genetics , Arabidopsis/genetics , Bacterial Proteins/genetics , Host-Pathogen Interactions/genetics , Plant Immunity/genetics , Plant Stomata/immunology , ADP Ribose Transferases/metabolism , Arabidopsis/immunology , Host-Pathogen Interactions/immunology , Plant Stomata/genetics , Plants, Genetically Modified , Proteomics , Pseudomonas syringae/metabolism , Pseudomonas syringae/pathogenicity , Type III Secretion Systems/genetics , Type III Secretion Systems/metabolismABSTRACT
The primary cilium is required for Hedgehog (Hh) signaling in vertebrates. Hh leads to ciliary accumulation and activation of the transmembrane protein Smoothened (Smo) and affects the localization of several pathway components, including the Gli family of transcriptional regulators, within different regions of primary cilia. Genetic analysis indicates that the kinesin protein Kif7 both promotes and inhibits mouse Hh signaling. Using mass spectrometry, we identified liprin-α1 (PPFIA1) and the protein phosphatase PP2A as Kif7-interacting proteins, and we showed that they were important for the trafficking of Kif7 and Gli proteins to the tips of cilia and for the transcriptional output of Hh signaling. Our results suggested that PPFIA1 functioned with PP2A to promote the dephosphorylation of Kif7, triggering Kif7 localization to the tips of primary cilia and promoting Gli transcriptional activity.
Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , Hedgehog Proteins/metabolism , Kinesins/metabolism , Protein Phosphatase 2/metabolism , Proteins/metabolism , Signal Transduction/physiology , Zebrafish Proteins/metabolism , Zebrafish/metabolism , Adaptor Proteins, Signal Transducing/genetics , Animals , Cilia/genetics , Cilia/metabolism , HEK293 Cells , Hedgehog Proteins/genetics , Humans , Kinesins/genetics , Kruppel-Like Transcription Factors/genetics , Kruppel-Like Transcription Factors/metabolism , Mice , Protein Phosphatase 2/genetics , Proteins/genetics , Transcription Factors/genetics , Transcription Factors/metabolism , Transcription, Genetic/physiology , Zebrafish/genetics , Zebrafish Proteins/genetics , Zinc Finger Protein GLI1ABSTRACT
The eukaryotic cytoskeleton is essential for structural support and intracellular transport, and is therefore a common target of animal pathogens. However, no phytopathogenic effector has yet been demonstrated to specifically target the plant cytoskeleton. Here we show that the Pseudomonas syringae type III secreted effector HopZ1a interacts with tubulin and polymerized microtubules. We demonstrate that HopZ1a is an acetyltransferase activated by the eukaryotic co-factor phytic acid. Activated HopZ1a acetylates itself and tubulin. The conserved autoacetylation site of the YopJ / HopZ superfamily, K289, plays a critical role in both the avirulence and virulence function of HopZ1a. Furthermore, HopZ1a requires its acetyltransferase activity to cause a dramatic decrease in Arabidopsis thaliana microtubule networks, disrupt the plant secretory pathway and suppress cell wall-mediated defense. Together, this study supports the hypothesis that HopZ1a promotes virulence through cytoskeletal and secretory disruption.
