The PML tumor suppressor controls key pathways for growth suppression, induction of apoptosis, and cellular senescence. PML loss occurs frequently in human tumors through unknown posttranslational mechanisms. Casein kinase 2 (CK2) is oncogenic and frequently upregulated in human tumors. Here we show that CK2 regulates PML protein levels by promoting its ubiquitin-mediated degradation dependent on direct phosphorylation at Ser517. Consequently, PML mutants that are resistant to CK2 phosphorylation display increased tumor-suppressive functions. In a faithful mouse model of lung cancer, we demonstrate that Pml inactivation leads to increased tumorigenesis. Furthermore, CK2 pharmacological inhibition enhances the PML tumor-suppressive property in vivo. Importantly, we found an inverse correlation between CK2 kinase activity and PML protein levels in human lung cancer-derived cell lines and primary specimens. These data identify a key posttranslational mechanism that controls PML protein levels and provide therapeutic means toward PML restoration through CK2 inhibition.
Pubmed ID: 16873060 RIS Download
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Computational biology resource for investigating candidate functional sites in eukarytic proteins. Functional sites which fit to the description linear motif are currently specified as patterns using Regular Expression rules. To improve the predictive power, context-based rules and logical filters are being developed and applied to reduce the amount of false positives. The current version of the ELM server provides core functionality including filtering by cell compartment, phylogeny, globular domain clash (using the SMART/Pfam databases) and structure. In addition, both the known ELM instances and any positionally conserved matches in sequences similar to ELM instance sequences are identified and displayed (see ELM instance mapper). Although the ELM resource contains a large collection of functional site motifs, the current set of motifs is not exhaustive.
View all literature mentionsScansite searches for motifs within proteins that are likely to be phosphorylated by specific protein kinases or bind to domains such as SH2 domains, 14-3-3 domains or PDZ domains. The Motifscanner program utilizes an entropy approach that assesses the probability of a site matching the motif using the selectivity values and sums the logs of the probability values for each amino acid in the candidate sequence. The program then indicates the percentile ranking of the candidate motif in respect to all potential motifs in proteins of a protein database. When available, percentile scores of some confirmed phosphorylation sites for the kinase of interests or confirmed binding sites of the domain of interest are provided for comparison with the scores of the candidate motifs.
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