Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The secreted signaling molecule Hedgehog regulates gene expression in target cells in part by preventing proteolysis of the full-length Cubitus interruptus (Ci-155) transcriptional activator to the Ci-75 repressor form. Ci-155 proteolysis depends on phosphorylation at three sites by Protein Kinase A (PKA). We show that these phosphoserines prime further phosphorylation at adjacent Glycogen Synthase Kinase 3 (GSK3) and Casein Kinase I (CK1) sites. Alteration of the GSK3 or CK1 sites prevents Ci-155 proteolysis and activates Ci in the absence of Hedgehog. Ci-155 proteolysis is also inhibited if cells lack activity of the Drosophila GSK3, Shaggy, previously implicated in Wingless signaling. Conversely, Ci-155 levels are reduced in Hedgehog-responding cells by overexpression of PKA and the Drosophila CK1, Double-time, a regulator of circadian rhythms.
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PMID:Proteolysis of the Hedgehog signaling effector Cubitus interruptus requires phosphorylation by Glycogen Synthase Kinase 3 and Casein Kinase 1. 1195 35

In the hedgehog signaling network, mutations result in various phenotypes, including, among others, holoprosencephaly, nevoid basal cell carcinoma syndrome, Pallister-Hall syndrome, Greig cephalopolysyndactyly, Rubinstein-Taybi syndrome, isolated basal cell carcinoma, and medulloblastoma. Active Hedgehog ligand is double lipid modified with a C-terminal cholesterol moiety and an N-terminal palmitate. Transport active Hedgehog from the signaling cell to the responding cell occurs through three mechanisms: 1). formation of multimeric Hedgehog which makes it soluble; 2). function of Dispatched in releasing the lipid-anchored protein from the signaling cell; and 3). movement across the plasma membrane of the responding cell by Tout-velu-dependent synthesis of heparan sulfate proteoglycan. In the responding cell, active Hedgehog binds to its receptor Patched, a 12-pass transmembrane protein, which frees Smoothened, an adjacent 7-pass transmembrane protein, for downstream signaling. Patched and Smoothened may shuttle oppositely between the plasma membrane and endocytic vesicles in response to active Hedgehog ligand. In downstream signaling, Cubitus interruptus (Gli proteins in vertebrates), Costal 2, Fused, and Suppressor of Fused form a tetrameric complex. Cubitus interruptus is a bifunctional transcription regulator. In the absence of active Hedgehog ligand, a truncated transcriptional repressor is generated that binds target genes and blocks their transcription. In the presence of active Hedgehog ligand, a full length transcriptional activator binds target genes and upregulates their transcription. Target genes include Wingless (Wnt gene family in vertebrates), Decapentaplegic (Bone Morphogenetic Proteins in vertebrates), and Patched. The upregulation of Patched expression, resulting in Patched protein at the cell membrane, sequesters Hedgehog and limits its spread beyond the cells in which it is produced. Thus, a balance is created by the antagonism of Hedgehog and Patched, whose relative concentrations alternate with respect to each other. Many more factors that are essential for the hedgehog signaling network are also discussed: Megalin, Rab23, Hip, GAS1, PKA, GSK3, CK1, Slimb, SAP18, and CBP.
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PMID:The hedgehog signaling network. 1455 42

Frequency (FRQ) and its transcriptional activator, the White Collar Complex (WCC), are essential components of interconnected feedback loops of the circadian clock of Neurospora. In a negative feedback loop, FRQ inhibits the WCC by recruiting casein kinase 1a (CK1a) and supporting its phosphorylation. In an interconnected positive loop, FRQ supports accumulation of high levels of WCC. Phosphorylation of clock proteins is crucial for the temporal and spatial coordination of these functions. We identified three isoforms of CK1a generated by alternative splicing that all interact with FRQ. Furthermore, we show that WC-2 is phosphorylated by CK1a in vitro and that WC-2 phosphorylation is inhibited in vivo by the CK1-specific inhibitor IC261. Finally, we demonstrate that CK1a activity regulates levels of WC-2.
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PMID:Posttranslational regulation of Neurospora circadian clock by CK1a-dependent phosphorylation. 1841 75

Hypoxia-inducible factor 1 (HIF-1), a transcriptional activator that mediates cellular response to hypoxia and a promising target of anticancer therapy, is essential for adaptation to low oxygen conditions, embryogenesis and tumor progression. HIF-1 is a heterodimer of HIF-1alpha, expression of which is controlled by oxygen levels as well as by various oxygen-independent mechanisms, and HIF-1beta (or ARNT), which is constitutively expressed. In this work, we investigate the phosphorylation of the N-terminal heterodimerization (PAS) domain of HIF-1alpha and identify Ser247 as a major site of in vitro modification by casein kinase 1delta (CK1delta). Mutation of this site to alanine, surprisingly, enhanced the transcriptional activity of HIF-1alpha, a result phenocopied by inhibition or small interfering RNA (siRNA)-mediated silencing of CK1delta under hypoxic conditions. Conversely, overexpression of CK1delta or phosphomimetic mutation of Ser247 to aspartate inhibited HIF-1alpha activity without affecting its stability or nuclear accumulation. Immunoprecipitation and in vitro binding experiments suggest that CK1-dependent phosphorylation of HIF-1alpha at Ser247 impairs its association with ARNT, a notion also supported by modeling the structure of the complex between HIF-1alpha and ARNT PAS-B domains. We suggest that modification of HIF-1alpha by CK1 represents a novel mechanism that controls the activity of HIF-1 during hypoxia by regulating the interaction between its two subunits.
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PMID:Casein kinase 1 regulates human hypoxia-inducible factor HIF-1. 2069 59