Neddylation is Essential for beta-catenin Degradation in Wnt Signaling Pathway
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo Sapiens
SUBMITTER: 
Xisong Ke
PROVIDER: PXD031303 | iProX | Thu Jan 27 00:00:00 GMT 2022
REPOSITORIES: iProX
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Project description:Wnt/β-catenin signaling is a highly organized biochemical cascade that triggers a gene expression program in the signal-receiving cell. The Wnt/β-catenin -driven transcriptional response is involved in virtually all cellular processes during development, homeostasis, and its deregulation causes human disease. However, outstanding questions remain unanswered. Among these, one regards how the Wnt/β-catenin cascade modulates the chromatin behavior: to date, there exists no comprehensive genome-wide annotation of changing chromatin patterns upon Wnt pathway activation. This is important, as shifts in chromatin patterns might underlie how different cells promote diverging gene expression programs in response to Wnt. To address this question, we characterized how Wnt/β-catenin signaling shapes the genome-wide chromatin accessibility landscape in two human cell types, human embryonic kidney cells 293T (HEK293T) and human embryonic stem cells (hESCs), over time. To this end, we treated HEK293T and hESCs with the GSK3 inhibitor/Wnt activator CHIR99021 (10 mM) for 3 days and assessed chromatin accessibility via ATAC-sequencing 4 hours, 24 hours and 3 days after the onset of the stimulation. We found that hESCs respond to Wnt/β-catenin activation by progressively shaping their chromatin accessibility profile in a manner that is consistent with their gradual acquisition of a mesodermal identity: differentiation genes loci open over time, while pluripotency ones close. We refer to this genomic response as plastic. On the other hand, HEK293T, which are known to be highly responsive to Wnt activation, appear more resistant to a long-term Wnt/β-catenin-driven change in cell identity. In this context, the chromatin displays a temporary opening of relevant regions at 4 hours after stimulation, followed by a re-establishment of its pre-stimulation state: we define this transient response as elastic.
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Project description:Background: Wnt signaling maintains the undifferentiated state of intestinal crypt progenitor cells by inducing the formation of nuclear TCF4/beta-catenin complexes. In colorectal cancer, activating mutations in Wnt pathway components cause inappropriate activation of TCF4/beta-catenin -driven transcription. Despite the passage of a decade after the discovery of TCF4 and beta-catenin as the molecular effectors of the Wnt signal, few transcriptional activators essential and unique to the regulation of this transcription program have been found. Methodology/Principal Findings: Using proteomics, we identified the leukemia-associated Mllt10/Af10 and the methyltransferase Dot1l, as Tcf4/beta-catenin interactors in mouse small intestinal crypts. Mllt10/Af10-Dot1l, essential for transcription elongation, are recruited to Wnt target genes in a beta-catenin -dependent manner, resulting in H3K79 methylation over their coding regions in vivo in proliferative crypts of mouse small intestine, in colorectal cancer and Wnt-inducible HEK293T cells. Depletion of MLLT10/AF10 in colorectal cancer and Wnt-inducible HEK293T cells followed by expression array analysis identifies MLLT10/AF10 and DOT1L as essential activators dedicated to Wnt target gene regulation. In contrast, previously published b-catenin coactivators p300 and beta-catenin displayed a more pleiotropic target gene expression profile controlling Wnt and other pathways. tcf4, mllt10/af10 and dot1l are co-expressed in Wnt-driven tissues in zebrafish and essential for Wnt-reporter activity. Intestinal differentiation defects in apc-mutant zebrafish can be rescued by depletion of Mllt10 and Dot1l, establishing these genes as activators downstream of Apc in Wnt target gene activation in vivo. Morpholino-depletion of mllt10/af10-dot1l in zebrafish results in defects in intestinal homeostasis and a significant reduction in the in vivo expression of direct Wnt target genes and in the number of proliferative intestinal epithelial cells. Conclusions/Significance: We conclude that Mllt10/Af10-Dot1l are essential, dedicated activators of Wnt-dependent transcription, critical for maintenance of intestinal proliferation and homeostasis. The methyltransferase Dot1l may present an attractive candidate for drug targeting in colorectal cancer. 6 samples for Ls174T cells: si-b-catenin against si-control and dyeswap of it, si-control, si-MLLT10, si-BRG1 and si-P300 are hybridized against common reference RNA; 6 samples of HEK293T cells: Wnt3A or control medium (CM) induction for 9 hours, si-MLLT10, si-DOT1L, si-BRG1 and si-P300 upon 9 hour Wnt3A induction are all hybridized against common reference RNA
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Project description:Wnt/β-catenin signaling is a highly organized biochemical cascade that triggers a gene expression program in the signal-receiving cell. The Wnt/β-catenin-driven transcriptional response is involved in virtually all cellular processes during development, homeostasis, and its deregulation causes human disease. However, outstanding questions remain unanswered. A first question concerns cell-specificity: how this response is integrated into lineage-specific choices is still unknown. A second question concerns time: it is not known whether β-catenin associates with its targets simultaneously or in a time-dependent fashion. For instance, while TCF/LEF and other components of the Wnt transcriptional complex are constitutively associated with the chromatin, it is β-catenin arrival, upon Wnt induction, that launches target genes transcription. Therefore, discovering the dynamics of the genome-wide β-catenin binding pattern is required to unambiguously define the direct targets of Wnt signaling To address these questions, we realized a time-resolved atlas of β-catenin genome-wide occupancy in two human cell types, human embryonic kidney cells 293T (HEK293T) and human embryonic stem cells (hESCs). To this end, we treated HEK293T and hESCs with the GSK3 inhibitor/Wnt activator CHIR99021 (10 mM) for 3 days, and assessed β-catenin binding via CUT&RUN-LoV-U (Zambanini et al., 2022) 90 minutes, 4 hours, 24 hours and 3 days after the onset of the stimulation. This approach allowed us to establish that β-catenin repositions to different genomic loci along stimulation time, showing that a definition of Wnt target genes must take into account the time-dimension. Moreover, β-catenin physical targets are largely cell-type specific, as only a subset of them is present across the examined contexts.
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