The human gene (CSNK2A1) coding for the casein kinase II subunit alpha is located on chromosome 20 and contains tandemly arranged Alu repeats

Targeting Protein Kinases to Protect Beta-Cell Function and Survival in Diabetes

The prevalence of diabetes is increasing worldwide. Massive death of pancreatic beta-cells causes type 1 diabetes. Progressive loss of beta-cell function and mass characterizes type 2 diabetes. To date, none of the available antidiabetic drugs promotes the maintenance of a functional mass of endogenous beta-cells, revealing an unmet medical need. Dysfunction and apoptotic death of beta-cells occur, in particular, through the activation of intracellular protein kinases. In recent years, protein kinases have become highly studied targets of the pharmaceutical industry for drug development. A number of drugs that inhibit protein kinases have been approved for the treatment of cancers. The question of whether safe drugs that inhibit protein kinase activity can be developed and used to protect the function and survival of beta-cells in diabetes is still unresolved. This review presents arguments suggesting that several protein kinases in beta-cells may represent targets of interest for the development of drugs to treat diabetes.

Casein Kinase 2 Affects Epilepsy by Regulating Ion Channels: A Potential Mechanism

Epilepsy, characterized by recurrent seizures and abnormal brain discharges, is the third most common chronic disorder of the Central Nervous System (CNS). Although significant progress has been made in the research on antiepileptic drugs (AEDs), approximately one-third of patients with epilepsy are refractory to these drugs. Thus, research on the pathogenesis of epilepsy is ongoing to find more effective treatments. Many pathological mechanisms are involved in epilepsy, including neuronal apoptosis, mossy fiber sprouting, neuroinflammation, and dysfunction of neuronal ion channels, leading to abnormal neuronal excitatory networks in the brain. CK2 (Casein kinase 2), which plays a critical role in modulating neuronal excitability and synaptic transmission, has been shown to be associated with epilepsy. However, there is limited research on the mechanisms involved. Recent studies have suggested that CK2 is involved in regulating the function of neuronal ion channels by directly phosphorylating them or their binding partners. Therefore, in this review, we will summarize recent research advances regarding the potential role of CK2 regulating ion channels in epilepsy, aiming to provide more evidence for future studies.

CK2 and protein kinases of the CK1 superfamily as targets for neurodegenerative disorders

Casein kinases are involved in a variety of signaling pathways, and also in inflammation, cancer, and neurological diseases. Therefore, they are regarded as potential therapeutic targets for drug design. Recent studies have highlighted the importance of the casein kinase 1 superfamily as well as protein kinase CK2 in the development of several neurodegenerative pathologies, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. CK1 kinases and their closely related tau tubulin kinases as well as CK2 are found to be overexpressed in the mammalian brain. Numerous substrates have been detected which play crucial roles in neuronal and synaptic network functions and activities. The development of new substances for the treatment of these pathologies is in high demand. The impact of these kinases in the progress of neurodegenerative disorders, their bona fide substrates, and numerous natural and synthetic compounds which are able to inhibit CK1, TTBK, and CK2 are discussed in this review.

Protein kinase CK2 and ion channels (Review)

Protein kinase CK2 appears as a tetramer or higher molecular weight oligomer composed of catalytic CK2α, CK2α' subunits and non-catalytic regulatory CK2β subunits or as individual subunits. It is implicated in a variety of different regulatory processes, such as Akt signalling, splicing and DNA repair within eukaryotic cells. The present review evaluates the influence of CK2 on ion channels in the plasma membrane. CK2 phosphorylates platform proteins such as calmodulin and ankyrin G, which bind to channel proteins for a physiological transport to and positioning into the membrane. In addition, CK2 directly phosphorylates a variety of channel proteins directly to regulate opening and closing of the channels. Thus, modulation of CK2 activities by specific inhibitors, by siRNA technology or by CRISPR/Cas technology has an influence on intracellular ion concentrations and thereby on cellular signalling. The physiological regulation of the intracellular ion concentration is important for cell survival and correct intracellular signalling. Disturbance of this regulation results in a variety of different diseases including epilepsy, heart failure, cystic fibrosis and diabetes. Therefore, these effects should be considered when using CK2 inhibition as a treatment option for cancer.

Protein Kinase CK2-A Putative Target for the Therapy of Diabetes Mellitus?

Since diabetes is a global epidemic, the development of novel therapeutic strategies for the treatment of this disease is of major clinical interest. Diabetes is differentiated in two types: type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). T1DM arises from an autoimmune destruction of insulin-producing β-cells whereas T2DM is characterized by an insulin resistance, an impaired insulin reaction of the target cells, and/or dysregulated insulin secretion. In the past, a growing number of studies have reported on the important role of the protein kinase CK2 in the regulation of the survival and endocrine function of pancreatic β-cells. In fact, inhibition of CK2 is capable of reducing cytokine-induced loss of β-cells and increases insulin expression as well as secretion by various pathways that are regulated by reversible phosphorylation of proteins. Moreover, CK2 inhibition modulates pathways that are involved in the development of diabetes and prevents signal transduction, leading to late complications such as diabetic retinopathy. Hence, targeting CK2 may represent a novel therapeutic strategy for the treatment of diabetes.

Extending the phenotype associated with the CSNK2A1-related Okur-Chung syndrome-A clinical study of 11 individuals

Variants in the Protein Kinase CK2 alpha subunit, encoding the CSNK2A1 gene, have previously been reported in children with an intellectual disability and dysmorphic facial features syndrome: now termed the Okur-Chung neurodevelopmental syndrome. More recently, through trio-based exome sequencing undertaken by the Deciphering Developmental Disorders Study (DDD study), a further 11 children with de novo CSNK2A1 variants have been identified. We have undertaken detailed phenotyping of these patients. Consistent with previously reported patients, patients in this series had apparent intellectual disability, swallowing difficulties, and hypotonia. While there are some shared facial characteristics, the gestalt is neither consistent nor readily recognized. Congenital heart abnormalities were identified in nearly 30% of the patients, representing a newly recognized CSNK2A1 clinical association. Based upon the clinical findings from this study and the previously reported patients, we suggest an initial approach to the management of patients with this recently described intellectual disability syndrome.

Characterizing the convergence of protein kinase CK2 and caspase-3 reveals isoform-specific phosphorylation of caspase-3 by CK2α': implications for pathological roles of CK2 in promoting cancer cell survival

Protein kinase CK2 has emerged as a promising candidate for the treatment of a number of cancers. This enzyme is comprised of two catalytic subunits (CK2 and/or CK2α′) that form complexes with homodimers of regulatory CK2β subunits. While catalytic and regulatory CK2 subunits are generally expressed at similar levels to form tetrameric complexes, asymmetric expression of CK2 subunits has been associated with various forms of cancer and the enhanced survival of cancer cells. To elucidate mechanisms responsible for regulation of cancer cell survival by CK2, we recently employed computational and experimental strategies that revealed widespread overlap between sites for CK2 phosphorylation and caspase cleavage. Among candidates with overlapping CK2 and caspase cleavage sites was caspase-3 that is phosphorylated by CK2 to prevent its activation by upstream caspases. To elucidate the precise relationship between CK2 and caspase-3, we modulated expression of individual CK2 subunits and demonstrated that CK2α′ exhibits a striking preference for caspase-3 phosphorylation in cells as compared to CK2α and that CK2β exhibits the capacity to abolish caspase-3 phosphorylation. Since caspase-3 represents the first CK2 substrate selectively phosphorylated by CK2α′ in cells, our work highlights divergent functions of the different forms of CK2. Given the involvement of CK2 in a diverse series of biological events and its association with various cancers, this work has important implications for identifying pathological roles of distinct forms of CK2 that could instruct efforts to selectively target individual CK2 subunits for therapy.

The cytosolic protein kinase CK2 phosphorylates cardiac calsequestrin in intact cells

The luminal SR protein CSQ2 contains phosphate on roughly half of the serines found in its C-terminus. The sequence around phosphorylation sites in CSQ2 suggest that the in vivo kinase is protein kinase CK2, even though this enzyme is thought to be present only in the cytoplasm and nucleus. To test whether CSQ2 kinase is CK2, we combined approaches that reduced CK2 activity and CSQ2 phosphorylation in intact cells. Tetrabromocinnamic acid, a specific inhibitor of CK2, inhibited both the CSQ2 kinase and CK2 in parallel across a range of concentrations. In intact primary adult rat cardiomyocytes and COS cells, 24 h of drug treatment reduced phosphorylation of overexpressed CSQ2 by 75%. Down-regulation of CK2α subunits in COS cells using siRNA, produced a 90% decrease in CK2α protein levels, and CK2-silenced COS cells exhibited a twofold reduction in CSQ2 kinase activity. Phosphorylation of CSQ2 overexpressed in CK2-silenced cells was also reduced by a factor of two. These data suggested that CSQ2 in intact cells is phosphorylated by CK2, a cytosolic kinase. When phosphorylation site mutants were analyzed in COS cells, the characteristic rough endoplasmic reticulum form of the CSQ2 glycan (GlcNAc2Man9,8) underwent phosphorylation site dependent processing such that CSQ2-nonPP (Ser to Ala mutant) and CSQ2-mimPP (Ser to Glu mutant) produced apparent lower and greater levels of ER retention, respectively. Taken together, these data suggest CK2 can phosphorylate CSQ2 co-translationally at biosynthetic sites in rough ER, a process that may result in changes in its subsequent trafficking through the secretory pathway.

Functional polymorphism of the CK2alpha intronless gene plays oncogenic roles in lung cancer

Protein kinase CK2 is frequently up-regulated in human cancers, although the mechanism of CK2 activation in cancer remains unknown. In this study, we investigated the role of the CK2α intronless gene (CSNK2A1P, a presumed CK2α pseudogene) in the pathogenesis of human cancers. We found evidence of amplification and over-expression of the CSNK2A1P gene in non- small cell lung cancer and leukemia cell lines and 25% of the lung cancer tissues studied. The mRNA expression levels correlated with the copy numbers of the CSNK2A1P gene. We also identified a novel polymorphic variant (398T/C, I133T) of the CSNK2A1P gene and showed that the 398T allele is selectively amplified over the 398C allele in 101 non-small cell lung cancer tissue samples compared to those in 48 normal controls (p = 0.013<0.05). We show for the first time CSNK2A1P protein expression in transfected human embryonic kidney 293T and mouse embryonic fibroblast NIH-3T3 cell lines. Both alleles are transforming in these cell lines, and the 398T allele appears to be more transforming than the 398C allele. Moreover, the 398T allele degrades PML tumor suppressor protein more efficiently than the 398C allele and shows a relatively stronger binding to PML. Knockdown of the CSNK2A1P gene expression with specific siRNA increased the PML protein level in lung cancer cells. We report, for the first time, that the CSNK2A1P gene is a functional proto-oncogene in human cancers and its functional polymorphism appears to degrade PML differentially in cancer cells. These results are consistent with an important role for the 398T allele of the CSNK2A1P in human lung cancer susceptibility.

Validation of protein kinase CK2 as oncological target

Protein kinase CK2 is a highly conserved enzyme composed of two catalytic subunits alpha and/or alpha' and two regulatory subunits beta whose activity is elevated in diverse tumour types as well as in highly proliferating tissues. Several results suggest that the overexpression of either CK2 catalytic subunits or the CK2 holoenzyme contributes to cellular transformation. In a similar vein, experiments performed compromising the intracellular expression of CK2 has led to somehow contradictory results with respect to the ability of this enzyme to control survival and apoptosis. To better elucidate the role of CK2 in programmed cell death, we have depleted cells of CK2 catalytic subunits by the application of antisense oligodeoxynucleotides and siRNAs techniques, respectively. Our results indicate that protein kinase CK2 is characterized by an extremely high stability that might be due to its association with other intracellular proteins, enhanced half-life or lower vulnerability towards proteolytic degradation. In addition, we show that despite the effectiveness of the methods applied in lowering CK2 kinase activity in all cells investigated, CK2 might not by itself be sufficient to trigger enhanced drug-induced apoptosis in cells.

The catalytic subunit alpha' gene of human protein kinase CK2 (CSNK2A2): genomic organization, promoter identification and determination of Ets1 as a key regulator

The human genome contains four protein kinase CK2 loci, enclosing three active genes coding for the catalytic subunits alpha and alpha' and the regulatory subunit beta, and a processed alpha subunit pseudogene. Extensive structure and transcriptional control data of the genes are available, except for the CK2alpha' gene (CSNK2A2). Using in silico and experimental approaches, we find CSNK2A2 to be located on the long arm of chromosome 16 (in contrast to published data), to span 40kb and to consist of 12 exons, with the translational start in Exon 1 and the stop in Exon 11. Exon/intron boundaries conform to the gt/ag rule, and various potential polyadenylation signals determine transcript species with lengths of 1.7-5.7 kb. The upstream region of the gene displays housekeeping characteristics, lacking a TATA box and possessing several GC boxes as well as a CpG island around Exon 1. According to reporter gene assay results, the promoter activity ranges from -1308 to 197 with the highest activity in region -396 to -129. This region contains binding motifs for various transcription factors, including NFkappaB, Sp and Ets family members. Site-directed mutagenesis indicates that the Ets motifs play, in cooperation with Sp motif clusters, a central role in regulating CK2alpha' gene transcription. A similar control has been described for the transcription of the CK2alpha and CK2beta genes so that the presented data are compatible with the assumption of a coordinate transcriptional regulation of all three active human CK2 genes decisively determined by Ets family members.

Casein Kinase II Alpha Subunit and C1-Inhibitor Are Independent Predictors of Outcome in Patients with Squamous Cell Carcinoma of the Lung

PURPOSE

Gene expression profiling has been shown to be a valuable tool for prognostication and identification of cancer-associated genes in human malignancies. We aimed to identify potential prognostic marker(s) in non-small cell lung cancers using global gene expression profiles.

EXPERIMENTAL DESIGN

Twenty-one previously untreated patients with non-small cell lung cancer were analyzed using the Affymetrix GeneChip high-density oligonucleotide array and comparative genomic hybridization. Identified candidate genes were validated in an independent cohort of 45 patients using quantitative real-time reverse transcription-PCR and Western blot analyses. Follow-up data for these patients was collected and used to assess outcome correlations.

RESULTS

Hierarchical clustering analysis yielded three distinct subgroups based on gene expression profiling. Cluster I consisted of 4 patients with adenocarcinoma and 1 with squamous cell carcinoma (squamous cell carcinoma); clusters II and III consisted of 6 and 10 patients with squamous cell carcinoma, respectively. Outcome analysis was performed on the cluster groups containing solely squamous cell carcinoma, revealing significant differences in disease-specific survival rates. Moreover, patients having a combination of advanced Tumor-Node-Metastasis stage and assigned to the poor prognosis cluster group (cluster II) had significantly poorer outcomes. Comparative genomic hybridization analysis showed recurrent chromosomal losses at 1p, 3p, 17, 19, and 22 and gains/amplifications at 3q, 5p, and 8q, which did not vary significantly between the cluster groups. We internally and externally validated a subset of 11 cluster II (poor prognosis)-specific genes having corresponding chromosomal aberrations identified by comparative genomic hybridization as prognostic markers in an independent cohort of patients with lung squamous cell carcinoma identifying CSNK2A1 and C1-Inh as independent predictors of outcome.

CONCLUSION

CSNK2A1 and C1-Inh are independent predictors of survival in lung squamous cell carcinoma patients and may be useful as prognostic markers.

Proapoptotic function of protein kinase CK2alpha" is mediated by a JNK signaling cascade

Protein kinase CK2 (formerly casein kinase II) is a tetrameric enzyme constitutively expressed in all eurakyotic tissues that plays a significant role in the regulation of cell proliferation, malignant transformation, and apoptosis. The catalytic alpha-subunit of the enzyme is known to exist in three isoforms CK2alpha, CK2alpha' and CK2alpha". CK2alpha" is highly expressed in liver compared with other tissues and is required for the normal trafficking of several hepatocellular membrane proteins. Initial studies of dengue virus infection indicated that the CK2alpha"-deficient membrane trafficking mutant cell line (Trf1) was resistant to virus-induced cell death compared with the parental human hepatoma (HuH)-7 hepatoma line. Expression of recombinant CK2alpha" in Trf1 was capable of reverting this resistant phenotype. This study was extended to TNF-alpha in addition to other stimuli of cell death in an attempt to uncover common death pathways that might be modulated by CK2alpha". Evaluation of different pathways involved in death signaling suggest that the regulation of a critical proapoptotic step in HuH-7 cells by CK2alpha" is mediated by a JNK signaling cascade.

Protein kinase CK2: structure, regulation and role in cellular decisions of life and death

Protein kinase CK2 ('casein kinase II') has traditionally been classified as a messenger-independent protein serine/threonine kinase that is typically found in tetrameric complexes consisting of two catalytic (alpha and/or alpha') subunits and two regulatory beta subunits. Accumulated biochemical and genetic evidence indicates that CK2 has a vast array of candidate physiological targets and participates in a complex series of cellular functions, including the maintenance of cell viability. This review summarizes current knowledge of the structural and enzymic features of CK2, and discusses advances that challenge traditional views of this enzyme. For example, the recent demonstrations that individual CK2 subunits exist outside tetrameric complexes and that CK2 displays dual-specificity kinase activity raises new prospects for the precise elucidation of its regulation and cellular functions. This review also discusses a number of the mechanisms that contribute to the regulation of CK2 in cells, and will highlight emerging insights into the role of CK2 in cellular decisions of life and death. In this latter respect, recent evidence suggests that CK2 can exert an anti-apoptotic role by protecting regulatory proteins from caspase-mediated degradation. The mechanistic basis of the observation that CK2 is essential for viability may reside in part in this ability to protect cellular proteins from caspase action. Furthermore, this anti-apoptotic function of CK2 may contribute to its ability to participate in transformation and tumorigenesis.

Translated Alu sequence determines nuclear localization of a novel catalytic subunit of casein kinase 2

Casein kinase 2 (CK2) is a tetrameric enzyme constitutively expressed in all eukaryotic tissues. The two known isoforms of the catalytic subunit, CK2alpha and CK2alpha', have been reported to have distinct tissue-dependent subcellular distributions. We recently described a third isoform of the catalytic subunit, designated CK2alpha", which is highly expressed in liver. Immunoblot analysis of HuH-7 human hepatoma cell fractions as well as immunofluorescent microscopy revealed that CK2alpha" was exclusively localized to the nucleus and preferentially associated with the nuclear matrix. CK2alpha and CK2alpha' were found in nuclear, membrane, and cytosolic compartments. Deletion of the carboxy-terminal 32 amino acids from the CK2alpha" sequence resulted in release of the truncated green fluorescent protein fusion protein from the nuclear matrix and redistribution to both the nucleus and the cytoplasm. Demonstration that the carboxy terminus is necessary but not sufficient for nuclear retention indicates that the underlying mechanism of CK2alpha" nuclear localization is dependent on the secondary structure of the holoenzyme directed by the carboxy-terminal sequence.

A novel t(16;20)(q22;p13) in polycythemia vera

We report a patient with polycythemia vera whose bone marrow cells carried a novel t(16;20)(q22;p13) as detected by karyotype analysis using G- and Q-banding techniques. The reciprocal translocation was confirmed by fluorescence in situ hybridization (FISH) using DNA libraries of chromosomes 16 and 20. To our knowledge, t(16;20)(q22;p13) has not been reported previously. The core binding factor beta (CBFbeta) gene located on 16q22 is known to be frequently involved in acute myelocytic leukemia. On the other hand, the 20p13 locus contains a gene encoding protein kinase CK2alpha, which is closely related to cell proliferation and cell cycle regulation. The t(16;20)(q22;p13) may be one of the cytogenetic aberrations in myeloproliferative disorders, and therefore, our observation warrants further studies on a possible involvement of the genes resulting from this translocation.

Functional conservation between the human, nematode, and yeast CK2 cell cycle genes

Protein kinase CK2 (formerly casein kinase II) is a highly conserved serine/threonine protein kinase ubiquitous in eukaryotic organisms. Previously, we have shown that CK2 is required for cell cycle progression and essential for the viability of the yeast Saccharomyces cerevisiae. We now report that either the human or the nematode Caenorhabditis elegans CK2alpha catalytic subunit can substitute for the yeast catalytic subunits. Additionally, expression of the human CK2 regulatory subunit (CK2beta) can suppress the temperature sensitivity of either of the two yeast CK2 mutant catalytic subunits. Taken together, these observations reinforce the view that the CK2 cell cycle progression genes have been highly conserved during evolution from yeast to humans, not only in structure but also in function.

Ets1 is a common element in directing transcription of the alpha and beta genes of human protein kinase CK2

Protein kinase CK2 is a conserved and vital Ser/Thr phosphotransferase with various links to malignant diseases, occurring as a tetramer composed of two catalytically active (CK2alpha and/or CK2alpha') and two regulatory subunits (CK2beta). There is balanced availability of CK2alpha and CK2beta transcripts in proliferating and differentiating cultured cells. Examination of the human CK2beta gene for transcriptionally active regions by systematic deletions and reporter gene assays indicates strong promoter activity at positions -42 to 14 and 12 to 72 containing transcription start sites 1 and 2 of the gene (positions +1 and 33), respectively, an upstream and a downstream enhancer activity at positions -241 to -168 and 123 to 677, respectively, and silencer activity at positions -241 to -261. Of the various transcription factor binding motifs present in those regions, Ets1 and CAAT-related motifs turned out to be of particular importance, Ets1 for promoter activation and CAAT-related motifs for enhancer activation. In addition, there are contributions by Sp1. Most strikingly, the Ets1 region representing two adjoining consensus motifs also occurs with complete identity in the recently characterized promoter of the CK2alpha gene [Krehan, A., Ansuini, H., Böcher, O., Grein, S., Wirkner, U. & Pyerin, W. (2001) J. Biol. Chem. 275, 18327-18336], and affects comparably, when assayed in parallel, the promoters of both CK2 genes, both by motif mutations and by Ets1 overexpression. The data strongly support the hypothesis that Ets1 acts as a common regulatory element of the CK2alpha and CK2beta genes involved in directing coordinate transcription and contributing to the balanced availability of transcripts.

A novel casein kinase 2 alpha-subunit regulates membrane protein traffic in the human hepatoma cell line HuH-7

A previously isolated endocytic trafficking mutant (TRF1) isolated from HuH-7 cells is defective in the distribution of subpopulations of cell-surface receptors for asialoorosomucoid (asialoglycoprotein receptor (ASGR)), transferrin, and mannose-terminating glycoproteins. The pleiotropic phenotype of TRF1 also includes an increased sensitivity to Pseudomonas toxin and deficient assembly and function of gap junctions. HuH-7xTRF1 hybrids exhibited a normal subcellular distribution of ASGR, consistent with the TRF1 mutation being recessive. A cDNA expression library derived from HuH-7 mRNA was transfected into TRF1 cells, which were subsequently selected for resistance to Pseudomonas toxin. Sequence analysis of a recovered cDNA revealed a unique isoform of casein kinase 2 (CK2), CK2alpha". Western blot analysis of TRF1 proteins revealed a 60% reduction in total CK2alpha expression. Consistent with this finding, the hybrids HuH-7xHuH-7 and HuH-7xTRF1 expressed equivalent amounts of total CK2alpha. Immunoblots using antibodies against peptides unique to the previously described CK2 isoforms CK2alpha and CK2alpha' and the novel CK2alpha" isoform showed that, although TRF1 and parental HuH-7 cells expressed comparable amounts of CK2alpha and CK2alpha', the mutant did not express CK2alpha". Based on the genomic DNA sequence, RNA transcripts encoding CK2alpha" apparently originate from alternative splicing of a primary transcript. Protein overexpression following transfection of TRF1 cells with cDNAs encoding either CK2alpha or the newly cloned CK2alpha" restored the parental HuH-7 phenotype, including Pseudomonas toxin resistance, cell-surface ASGR binding activity, phosphorylation, and the assembly of gap junctions. This study suggests that HuH-7 cells express at least three CK2alpha isoforms and that the pleiotropic TRF1 phenotype is a consequence of a reduction in total CK2 expression.

Resolution of conflicting assignments for the bovine casein kinase II alpha (CSNK2A2) gene

The casein kinase II alpha' gene (CSNK2A2), which physically maps to human chromosome 16 (HSA16), has previously been mapped to bovine chromosome 5 (BTA5). Based on these results, a new segment of homology between the human and bovine genomes was suggested. In this paper we demonstrate linkage between CSNK2A2 and several markers on BTA18. Our result is supported by the extensive conservation of synteny between HSA16q and BTA18. Bovine chromosome 18 markers used in this study included several microsatellites, as well as the MC1R gene previously mapped to HSA16q24.3. Sequencing of the PCR-fragment mapped to BTA5 reveals that a CSNK-like retroposon was responsible for the conflicting assignments. The present results further extend the observed conservation of synteny between HSA16q and BTA18.

Inducible expression of protein kinase CK2 in mammalian cells. Evidence for functional specialization of CK2 isoforms

Protein kinase CK2 (formerly casein kinase II) exhibits elevated expression in a variety of cancers, induces lymphocyte transformation in transgenic mice, and collaborates with Ha-Ras in fibroblast transformation. To systematically examine the cellular functions of CK2, human osteosarcoma U2-OS cells constitutively expressing a tetracycline-regulated transactivator were stably transfected with a bidirectional plasmid encoding either catalytic isoform of CK2 (i.e. CK2alpha or CK2alpha') together with the regulatory CK2beta subunit in order to increase the cellular levels of either CK2 isoform. To interfere with either CK2 isoform, cells were also transfected with kinase-inactive CK2alpha or CK2alpha' (i. e. GK2alpha (K68M) or CK2alpha'(K69M)) together with CK2beta. In these cells, removal of tetracycline from the growth medium stimulated coordinate expression of catalytic and regulatory CK2 subunits. Increased expression of active forms of CK2alpha or CK2alpha' resulted in modest decreases in cell proliferation, suggesting that optimal levels of CK2 are required for optimal proliferation. By comparison, the effects of induced expression of kinase-inactive CK2alpha differed significantly from the effects of induced expression of kinase-inactive CK2alpha'. Of particular interest is the dramatic attenuation of proliferation that is observed following induction of CK2alpha'(K69M), but not following induction of CK2alpha(K68M). These results provide evidence for functional specialization of CK2 isoforms in mammalian cells. Moreover, cell lines exhibiting regulatable expression of CK2 will facilitate efforts to systematically elucidate its cellular functions.

Serum-stimulated cell cycle entry of fibroblasts requires undisturbed phosphorylation and non-phosphorylation interactions of the catalytic subunits of protein kinase CK2

Protein kinase CK2 is a pleiotropic Ser/Thr kinase occurring as alpha2beta2, alpha'2beta2, or alphaalpha'beta2 tetramers. A requirement in serum-stimulated cell cycle entry in both the cytoplasm and the nucleus of human fibroblasts for phosphorylation(s) by CK2 has been concluded from stimulation inhibition by microinjected antibodies against the regulatory subunit (beta). We have now examined this idea more directly by microinjection-mediated perturbation of phosphorylation and non-phosphorylation interactions of the catalytic subunits (alpha and alpha'), and by verifying the supposed matching of the cellular partition of CK2 subunits in the fibroblasts employed. While immunostaining and cell fractionation indicate that the partitions of subunits indeed match each other (with their predominant location in the nucleus in both quiescent and serum-stimulated cells), microinjection of substrate or pseudosubstrate peptides competing for the CK2-mediated phosphorylation in vitro resulted in significant inhibition of serum stimulation when placed into the nucleus but not when placed into the cytoplasm. Also inhibitory were nuclear but not cytoplasmic injections of antibodies against alpha and alpha' that affect neither their kinase activity in vitro nor their complexing to beta. The data indicate that the role played by CK2 in serum-stimulated cell cycle entry is predominantly nuclear and more complex than previously assumed, involving not only phosphorylation but also experimentally separable non-phosphorylation interactions by the catalytic subunits.

Genomic organization and promoter identification of the human protein kinase CK2 catalytic subunit alpha (CSNK2A1)

The isolation and characterization of the complete gene coding for human protein kinase CK2 catalytic subunit alpha is described. The gene spans 70 kb and consists of 13 exons, and the exon/intron boundaries conform to the gt/ag rule. Exons range in size from 51 to 2960 bp, introns from 527 to around 34000 bp. The translation start site is located in Exon 2, the stop codon in Exon 13. Two transcription start sites were identified by primer extension analysis: The further 5'-located site defines position 1 of the gene, the second site is located at position 50. The 5' region of the CK2 alpha gene shows features of a housekeeping promoter, such as lack of a TATA box and presence of a CpG island and GC boxes. The region was analyzed by reporter gene assay, and promoter activity was detected within the region ranging from position -256 to 144. Six potential polyadenylation signals were identified in the 3' noncoding region of the CK2 alpha gene. As indicated by comparison with expressed sequence tags from the EMBL databank and by Northern-blot analysis, the most 3' located, active polyadenylation signal seems to be the fourth signal, defining the end of the gene.

Murine protein kinase CK2 alpha': cDNA and genomic cloning and chromosomal mapping

Protein kinase CK2 (casein kinase II) is a heterotetrameric enzyme implicated in many essential regulatory pathways in cells. We have determined the sequence of the murine CK2 alpha' cDNA that encodes a 350-amino-acid protein that would have 99 and 98% homology with the human and chicken proteins, respectively, and is also highly homologous to murine CK2 alpha. To clarify the sequence of the 5' end of the cDNA and to elucidate the structure and regulation of the gene, we obtained a bacterial artificial chromosome clone that contains the 35-kb CK2 alpha' gene. The gene consists of 12 small exons; the 5' end, including the first exon and intron, is extremely GC rich and contains a CpG island. The putative promoter contains potential binding sites for a variety of transcriptional factors but appears to lack CCAAT- or TATA-like elements. A polymorphic dinucleotide repeat in the fifth intron allowed us to map the CK2 alpha' gene to murine Chromosome 8.

Study of Alu sequences at the hypoxanthine phosphoribosyltransferase (hprt) encoding region of man

The hypoxanthine phosphoribosyltransferase (hprt) encoding region of man is considered rich in Alu sequences: with 49 sequences present within 57 kilobases. Subfamily classification of the Alu sequences and identification of flanking direct repeats has been carried out to detect past rearrangements associated with their insertion into the region. Members of the Alu-J and three Alu-S subfamilies are present, along with the existence of free left arm sequences. Using available data, a comparison is made of the Alu subfamilies present at different gene regions. The heterogeneity in the number of each subfamily present at different genes shows that no one particular subfamily attained saturation in the genome. Several adjacent insertions of Alu sequences are seen at the hprt region. Furthermore two novel sequences are described, there is an incident where one Alu sequence has inserted into the middle poly(A) tract of an existing sequence at the hprt region; while another result from an Alu/Alu cross-over event elsewhere in the genome, before insertion into the hprt region. Once inserted, the Alu sequences are rarely subject to loss or rearrangement.

Induced release of cell surface protein kinase yields CK1- and CK2-like enzymes in tandem

Several types of cell exhibit cell surface protein kinase (ecto-PK) activities with Ser/Thr-specificity. Ecto-PK sharing certain characteristics of protein kinase CK2 can be detached from intact cells by interaction with exogenous substrates (Kübler, D., Pyerin, W., Burow, E., and Kinzel, V. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 4021-4025). However, a detailed molecular analysis of this ecto-PK was hampered by the vanishingly small amounts of labile enzyme protein obtained by substrate-inducible enzyme release. We now describe the stabilization and enrichment of released ecto-PK by precipitation with polyethylene glycol followed by affinity chromatography on heparin-agarose. Ecto-PK is shown to consist of two separate forms released in tandem, ecto-PK I and ecto-PK II. Comparison with cell homogenates as well as cell surface biotinylation experiments excluded contamination with intracellular PK. Purified ecto-PK I and ecto-PK II exhibit respectively selective phosphorylation of CK1- and CK2-specific peptide substrates, a complementary sensitivity to inhibitory agents and a differential use of the cosubstrates ATP and GTP. Ecto-PK I consists of a 40-kDa moiety; the ecto-PK II is an ensemble of three components of 43- and 40-kDa (catalytic subunits) and a noncatalytic 28-kDa subunit. In addition, components of the ecto-PK II react with CK2-specific antibodies. Further, comparative peptide mapping and the results of mass spectrometry in combination with assignment of amino acid sequences confirmed that ecto-PK II is closely related if not identical to the protein kinase CK2. Assays with intact cells that result in the phosphorylation of a variety of endogenous membrane proteins showed that both ecto-PKs participate, and further, certain ecto-PK substrates become preferentially labeled by one or another of the enzymes, whereas others are phosphorylated by both ecto-PK activities.

Casein kinase II alpha transgene-induced murine lymphoma: relation to theileriosis in cattle

Infection of cattle with the protozoan parasite Theileria parva results in a fatal lymphoproliferative syndrome that is associated with the overexpression of casein kinase II. The role of this enzyme in the pathogenesis of lymphoproliferative disorders was investigated by expressing the catalytic subunit in lymphocytes of transgenic mice. Adult transgenic mice displayed a stochastic propensity to develop lymphoma; co-expression of a c-myc transgene in addition to casein kinase II resulted in neonatal leukemia. Thus, the casein kinase II gene can serve as an oncogene, and its dysregulated expression is capable of transforming lymphocytes in a two-step pathway with c-myc.

Human casein kinase II: structures, genes, expression and requirement in cell growth stimulation

Casein kinase II (CKII) is an ubiquitous Ser/Thr protein phosphotransferase in control of a variety of crucial cellular functions including metabolism, signal transduction, transcription, translation and replication. CKII levels are consistently higher in neoplastic tissues. The human CKII is composed of subunits alpha, alpha', and beta with molecular masses of 43, 38 and 28 kDa, respectively, that form heterotetrameric holoenzymes (alpha 2 beta 2; alpha alpha' beta 2, alpha'2 beta 2) showing autophosphorylation particularly at subunit beta and hence suspected to play a regulatory role. The amino acid sequences of subunits indicate high evolutionary conservation. Employing the complete set of tissue-derived (placenta) and recombinant (expressed in E. coli) subunits and CKII holoenzymes, the catalytic function of alpha and alpha' and the several-fold stimulation by beta is shown to occur comparably in tissue-derived and recombinant CKII and the autophosphorylation of beta is shown by site-directed mutagenesis to be not decisive for the tuning of CKII activity. The human genome contains two genes encoding CKII alpha. First, there is a processed (pseudo)gene which is 99% homologous to the CKII alpha cDNA and which possesses a promoter-like region adjacently upstream with TATA and CAAT boxes so that transcription cannot be excluded. Second, there is an active gene of which we have characterized so far a 18.9 kb long central fragment which contains 8 exons comprising bases 102-824 of the CKII alpha coding region. The gene fragment contains repetitive elements, most prominently 16 Alu repeats. The genome further contains one as yet uncharacterized CKII alpha' gene and one gene encoding CKII beta. The CKII beta gene has been characterized as a 4.2 kb spanning gene composed of seven exons which possesses three transcription start sites and the translation start site in the second exon. The first intron harbors an Alu repeat also. The promoter region of the CKII beta gene contains elements such as multiple GC boxes, a CpG island, and nonstandard-positioned CAAT boxes but lacks a TATA box thus characterizing the gene as a housekeeping gene. The CKII genes are not clustered at a certain chromosome but rather are distributed over the whole human genome. Using the genomic clones as the probes for in situ hybridization, the active CKII alpha gene was mapped to chromosome 20p13, the processed CKII alpha (pseudo)gene to chromosome 11p15, and the CKII beta gene to chromosome 6p21. (The CKII alpha' gene has been localized on chromosome 16 with a cDNA probe.).(ABSTRACT TRUNCATED AT 400 WORDS)