Duplication of a genomic region containing the Cdc2L1-2 and MMP21-22 genes on human chromosome 1p36.3 and their linkage to D1Z2

CDK11, a splicing-associated kinase regulating gene expression

The ability of a cell to properly express its genes depends on optimal transcription and splicing. RNA polymerase II (RNAPII) transcribes protein-coding genes and produces pre-mRNAs, which undergo, largely co-transcriptionally, intron excision by the spliceosome complex. Spliceosome activation is a major control step, leading to a catalytically active complex. Recent work has showed that cyclin-dependent kinase (CDK)11 regulates spliceosome activation via the phosphorylation of SF3B1, a core spliceosome component. Thus, CDK11 arises as a major coordinator of gene expression in metazoans due to its role in the rate-limiting step of pre-mRNA splicing. This review outlines the evolution of CDK11 and SF3B1 and their emerging roles in splicing regulation. It also discusses how CDK11 and its inhibition affect transcription and cell cycle progression.

Crystal structure of the CDK11 kinase domain bound to the small-molecule inhibitor OTS964

CDK11 is a cyclin-dependent kinase that controls proliferation by regulating transcription, RNA splicing, and the cell cycle. As its activity is increasingly associated with cancer, CDK11 is an attractive target for the development of small-molecule inhibitors. However, the development of CDK11 inhibitors with limited off-target effects against other CDKs poses a challenge based on the high conservation of sequence across family members. OTS964 is notable as it displays a measure of specificity for CDK11 in cells. To understand the basis for OTS964's specificity for CDK11, we solved a 2.6 Å crystal structure of the CDK11 kinase domain bound to OTS964. Despite the absence of cyclin, CDK11 adopts an active-like conformation when bound to OTS964. We identified amino acids likely to contribute to the specificity of OTS964 for CDK11 and assessed their contribution to OTS964 binding by isothermal titration calorimetry (ITC) in vitro and by resistance to OTS964 in cells.

CDK11 negatively regulates Wnt/β-catenin signaling in the endosomal compartment by affecting microtubule stability

Objectives: Improper activation of Wnt/β-catenin signaling has been implicated in human diseases. Beyond the well-studied glycogen synthase kinase 3β (GSK3β) and casein kinase 1 (CK1), other kinases affecting Wnt/β-catenin signaling remain to be defined. Methods:To identify the kinases that modulate Wnt/β-catenin signaling, we applied a kinase small interfering RNA (siRNA) library screen approach. Luciferase assays, immunoblotting, and real-time polymerase chain reaction (PCR) were performed to confirm the regulation of the Wnt/β-catenin signaling pathway by cyclin-dependent kinase 11 (CDK11) and to investigate the underlying mechanism. Confocal immunofluorescence, coimmunoprecipitation (co-IP), and scratch wound assays were used to demonstrate colocalization, detect protein interactions, and explore the function of CDK11. Results: CDK11 was found to be a significant candidate kinase participating in the negative control of Wnt/β-catenin signaling. Down-regulation of CDK11 led to the accumulation of Wnt/β-catenin signaling receptor complexes, in a manner dependent on intact adenomatosis polyposis coli (APC) protein. Further analysis showed that CDK11 modulation of Wnt/β-catenin signaling engaged the endolysosomal machinery, and CDK11 knockdown enhanced the colocalization of Wnt/β-catenin signaling receptor complexes with early endosomes and decreased colocalization with lysosomes. Mechanistically, CDK11 was found to function in Wnt/β-catenin signaling by regulating microtubule stability. Depletion of CDK11 down-regulated acetyl-α-tubulin. Moreover, co-IP assays demonstrated that CDK11 interacts with the α-tubulin deacetylase SIRT2, whereas SIRT2 down-regulation in CDK11-depleted cells reversed the accumulation of Wnt/β-catenin signaling receptor complexes. CDK11 was found to suppress cell migration through altered Wnt/β-catenin signaling. Conclusions: CDK11 is a negative modulator of Wnt/β-catenin signaling that stabilizes microtubules, thus resulting in the dysregulation of receptor complex trafficking from early endosomes to lysosomes.

Transcriptional activation of CBFβ by CDK11p110 is necessary to promote osteosarcoma cell proliferation

BACKGROUND

Aberrant expression of cyclin-dependent protein kinases (CDK) is a hallmark of cancer. CDK11 plays a crucial role in cancer cell growth and proliferation. However, the molecular mechanisms of CDK11 and CDK11 transcriptionally regulated genes are largely unknown.

METHODS

In this study, we performed a global transcriptional analysis using gene array technology to investigate the transcriptional role of CDK11 in osteosarcoma. The promoter luciferase assay, chromatin immunoprecipitation assay, and Gel Shift assay were used to identify direct transcriptional targets of CDK11. Clinical relevance and function of core-binding factor subunit beta (CBFβ) were further accessed in osteosarcoma.

RESULTS

We identified a transcriptional role of protein-DNA interaction for CDK11p110, but not CDK11p58, in the regulation of CBFβ expression in osteosarcoma cells. The CBFβ promoter luciferase assay, chromatin immunoprecipitation assay, and Gel Shift assay confirmed that CBFβ is a direct transcriptional target of CDK11. High expression of CBFβ is associated with poor outcome in osteosarcoma patients. Expression of CBFβ contributes to the proliferation and metastatic behavior of osteosarcoma cells.

CONCLUSIONS

These data establish CBFβ as a mediator of CDK11p110 dependent oncogenesis and suggest that targeting the CDK11- CBFβ pathway may be a promising therapeutic strategy for osteosarcoma treatment.

Off-target toxicity is a common mechanism of action of cancer drugs undergoing clinical trials

Ninety-seven percent of drug-indication pairs that are tested in clinical trials in oncology never advance to receive U.S. Food and Drug Administration approval. While lack of efficacy and dose-limiting toxicities are the most common causes of trial failure, the reason(s) why so many new drugs encounter these problems is not well understood. Using CRISPR-Cas9 mutagenesis, we investigated a set of cancer drugs and drug targets in various stages of clinical testing. We show that-contrary to previous reports obtained predominantly with RNA interference and small-molecule inhibitors-the proteins ostensibly targeted by these drugs are nonessential for cancer cell proliferation. Moreover, the efficacy of each drug that we tested was unaffected by the loss of its putative target, indicating that these compounds kill cells via off-target effects. By applying a genetic target-deconvolution strategy, we found that the mischaracterized anticancer agent OTS964 is actually a potent inhibitor of the cyclin-dependent kinase CDK11 and that multiple cancer types are addicted to CDK11 expression. We suggest that stringent genetic validation of the mechanism of action of cancer drugs in the preclinical setting may decrease the number of therapies tested in human patients that fail to provide any clinical benefit.

The emerging roles and therapeutic potential of cyclin-dependent kinase 11 (CDK11) in human cancer

Overexpression and/or hyperactivation of cyclin-dependent kinases (CDKs) are common features of most cancer types. CDKs have been shown to play important roles in tumor cell proliferation and growth by controlling cell cycle, transcription, and RNA splicing. CDK4/6 inhibitor palbociclib has been recently approved by the FDA for the treatment of breast cancer. CDK11 is a serine/threonine protein kinase in the CDK family and recent studies have shown that CDK11 also plays critical roles in cancer cell growth and proliferation. A variety of genetic and epigenetic events may cause universal overexpression of CDK11 in human cancers. Inhibition of CDK11 has been shown to lead to cancer cell death and apoptosis. Significant evidence has suggested that CDK11 may be a novel and promising therapeutic target for the treatment of cancers. This review will focus on the emerging roles of CDK11 in human cancers, and provide a proof-of-principle for continued efforts toward targeting CDK11 for effective cancer treatment.

Matrix metalloproteinase (MMP) -2, -7 and -9 promoter polymorphisms in colorectal cancer in ethnic Kashmiri population - A case-control study and a mini review

Matrix metalloproteinases (MMPs) are proteolytic enzymes that play a pivotal role in the transformation and progression of tumors at all stages, especially during the invasion and metastasis. The aim of this study was to determine the genetic association of MMP2, MMP7 and MMP9 promoter polymorphisms with colorectal cancer (CRC) susceptibility and development risk in ethnic Kashmiri population. The genotype frequencies of MMP2-1306C/T, MMP7-181A/G and MMP9-1562C/T SNPs were compared between 142 CRC patients and 184 healthy controls by using PCR-RFLP method. The association between all the three MMP promoter polymorphisms and the modulation of risk of CRC was found to be significant (p≤0.05). The heterozygous genotype (CT) of MMP2-1306C/T SNP and variant genotype (GG) of MMP7-181A/G SNP showed a significant association with decreased risk for the development of CRC [OR, 0.61 (95%CI, 0.37-1.01); p=0.05 and OR, 0.43 (95%CI, 0.20-0.90); p=0.02, respectively] whereas the heterozygous genotype (CT) of MMP9-1562C/T SNP showed a significant association with increased risk for the development of colorectal cancer [OR, 1.88 (95%CI, 1.11-3.18); p=0.02]. Further, the less common MMP9-1562T allele was found to be significantly associated with an increased risk of colorectal cancer [OR, 1.74 (95%CI, 1.15-2.62); p=0.007]. Our results suggest that these MMP2, MMP7 and MMP9 promoter polymorphisms play a role as one of the key modulators of the risk of developing colorectal cancer in Kashmiri population.

Cyclin-dependent kinase 11(p110) (CDK11(p110)) is crucial for human breast cancer cell proliferation and growth

Cyclin-dependent kinases (CDKs) play important roles in the development of many types of cancers by binding with their paired cyclins. However, the function of CDK11 larger protein isomer, CDK11(p110), in the tumorigenesis of human breast cancer remains unclear. In the present study, we explored the effects and molecular mechanisms of CDK11(p110) in the proliferation and growth of breast cancer cells by determining the expression of CDK11(p110) in breast tumor tissues and examining the phenotypic changes of breast cancer cells after CDK11(p110) knockdown. We found that CDK11(p110) was highly expressed in breast tumor tissues and cell lines. Tissue microarray analysis showed that elevated CDK11(p110) expression in breast cancer tissues significantly correlated with poor differentiation, and was also associated with advanced TNM stage and poor clinical prognosis for breast cancer patients. In vitro knockdown of CDK11(p110) by siRNA significantly inhibited cell growth and migration, and dramatically induced apoptosis in breast cancer cells. Flow cytometry demonstrated that cells were markedly arrested in G1 phase of the cell cycle after CDK11(p110) downregulation. These findings suggest that CDK11(p110) is critical for the proliferation and growth of breast cancer cells, which highlights CDK11(p110) may be a promising therapeutic target for the treatment of breast cancer.

Matrix metalloproteinases and gastrointestinal cancers: Impacts of dietary antioxidants

The process of carcinogenesis is tightly regulated by antioxidant enzymes and matrix degrading enzymes, namely, matrix metalloproteinases (MMPs). Degradation of extracellular matrix (ECM) proteins like collagen, proteoglycan, laminin, elastin and fibronectin is considered to be the prerequisite for tumor invasion and metastasis. MMPs can degrade essentially all of the ECM components and, most MMPs also substantially contribute to angiogenesis, differentiation, proliferation and apoptosis. Hence, MMPs are important regulators of tumor growth both at the primary site and in distant metastases; thus the enzymes are considered as important targets for cancer therapy. The implications of MMPs in cancers are no longer mysterious; however, the mechanism of action is yet to be explained. Herein, our major interest is to clarify how MMPs are tied up with gastrointestinal cancers. Gastrointestinal cancer is a variety of cancer types, including the cancers of gastrointestinal tract and organs, i.e., esophagus, stomach, biliary system, pancreas, small intestine, large intestine, rectum and anus. The activity of MMPs is regulated by its endogenous inhibitor tissue inhibitor of metalloproteinase (TIMP) which bind MMPs with a 1:1 stoichiometry. In addition, RECK (reversion including cysteine-rich protein with kazal motifs) is a membrane bound glycoprotein that inhibits MMP-2, -9 and -14. Moreover, α2-macroglobulin mediates the uptake of several MMPs thereby inhibit their activity. Cancerous conditions increase intrinsic reactive oxygen species (ROS) through mitochondrial dysfunction leading to altered protease/anti-protease balance. ROS, an index of oxidative stress is also involved in tumorigenesis by activation of different MAP kinase pathways including MMP induction. Oxidative stress is involved in cancer by changing the activity and expression of regulatory proteins especially MMPs. Epidemiological studies have shown that high intake of fruits that rich in antioxidants is associated with a lower cancer incidence. Evidence indicates that some antioxidants inhibit the growth of malignant cells by inducing apoptosis and inhibiting the activity of MMPs. This review is discussed in six subchapters, as follows.

The cyclin-dependent kinase PITSLRE/CDK11 is required for successful autophagy

(Macro)autophagy is a membrane-trafficking process that serves to sequester cellular constituents in organelles termed autophagosomes, which target their degradation in the lysosome. Autophagy operates at basal levels in all cells where it serves as a homeostatic mechanism to maintain cellular integrity. The levels and cargoes of autophagy can, however, change in response to a variety of stimuli, and perturbations in autophagy are known to be involved in the aetiology of various human diseases. Autophagy must therefore be tightly controlled. We report here that the Drosophila cyclin-dependent kinase PITSLRE is a modulator of autophagy. Loss of the human PITSLRE orthologue, CDK11, initially appears to induce autophagy, but at later time points CDK11 is critically required for autophagic flux and cargo digestion. Since PITSLRE/CDK11 regulates autophagy in both Drosophila and human cells, this kinase represents a novel phylogenetically conserved component of the autophagy machinery.

Mislocalization of CDK11/PITSLRE, a regulator of the G2/M phase of the cell cycle, in Alzheimer disease

Post-mitotic neurons are typically terminally differentiated and in a quiescent status. However, in Alzheimer disease (AD), many neurons display ectopic re-expression of cell cycle-related proteins. Cyclin-dependent kinase 11 (CDK11) mRNA produces a 110-kDa protein (CDK11^p110) throughout the cell cycle, a 58-kDa protein (CDK11^p58) that is specifically translated from an internal ribosome entry site and expressed only in the G₂/M phase of the cell cycle, and a 46-kDa protein (CDK11^p46) that is considered to be apoptosis specific. CDK11 is required for sister chromatid cohesion and the completion of mitosis. In this study, we found that the expression patterns of CDK11 vary such that cytoplasmic CDK11 is increased in AD cellular processes, compared to a pronounced nuclear expression pattern in most controls. We also investigated the effect of amyloid precursor protein (APP) on CDK11 expression in vitro by using M17 cells overexpressing wild-type APP and APP Swedish mutant phenotype and found increased CDK11 expression compared to empty vector. In addition, amyloid-β_25–35 resulted in increased CDK11 in M17 cells. These data suggest that CDK11 may play a vital role in cell cycle re-entry in AD neurons in an APP-dependent manner, thus presenting an intriguing novel function of the APP signaling pathway in AD.

Protective roles of matrix metalloproteinases: from mouse models to human cancer

Matrix metalloproteinases (MMPs) have long been linked to cancer progression owing to their ability to breakdown tissue barriers for metastatic spread. Accordingly, multiple studies have examined the potential value of these enzymes as targets for cancer therapy. Unfortunately, most clinical trials with MMP inhibitors have yielded negative results which has made necessary to re-evaluate the role of these proteases in cancer. Recent works mainly based on the use of mouse models deficient in specific MMPs have revealed that these enzymes play many roles in cancer distinct from matrix destruction, influencing early steps of tumor evolution, and expanding their pro-tumorigenic properties. However, these in vivo studies have also shown that, unexpectedly, some MMP family members like MMP8 may have paradoxical anti-tumor functions. Nevertheless, the final validation of these MMPs as bona fide tumor suppressors requested the identification of the putative genetic or epigenetic changes underlying their inactivation during cancer development. To this purpose, very recent large-scale genomic studies have explored the possibility that MMPs could be genetically altered in a panel of human malignant tumors from different sources. These studies have demonstrated that MMP8 is a frequently mutated gene in human melanoma. Functional analysis of the identified mutations has confirmed that all of them lead to the loss-of-function of MMP8 and enhance the progression of melanoma, thus providing definitive evidence that MMP8 is a tumor-suppressor gene. Parallel studies have extended these findings to other MMP-related metalloproteinases such as ADAMTS15, which has been found to be genetically inactivated in human colorectal cancer. This review describes the identification and validation of some MMPs and related enzymes as anti-tumor proteases and speculates about the molecular mechanisms underlying their protective roles in tumor development. Finally, the review explores the clinical applications derived from the identification of MMPs that favour the host instead of the tumor.

The annotation of both human and mouse kinomes in UniProtKB/Swiss-Prot: one small step in manual annotation, one giant leap for full comprehension of genomes

Biomolecule phosphorylation by protein kinases is a fundamental cell signaling process in all living cells. Following the comprehensive cataloguing of the protein kinase complement of the human genome (Manning, G., Whyte, D. B., Martinez, R., Hunter, T., and Sudarsanam, S. (2002) The protein kinase complement of the human genome. Science 298, 1912-1934), this review will detail the state-of-the-art human and mouse kinase proteomes as provided in the UniProtKB/Swiss-Prot protein knowledgebase. The sequences of the 480 classical and up to 24 atypical protein kinases now believed to exist in the human genome and 484 classical and up to 24 atypical kinases within the mouse genome have been reviewed and, where necessary, revised. Extensive annotation has been added to each entry. In an era when a wealth of new databases is emerging on the Internet, UniProtKB/Swiss-Prot makes available to the scientific community the most up-to-date and in-depth annotation of these proteins with access to additional external resources linked from within each entry. Incorrect sequence annotations resulting from errors and artifacts have been eliminated. Each entry will be constantly reviewed and updated as new information becomes available with the orthologous enzymes in related species being annotated in a parallel effort and complete kinomes being completed as sequences become available. This ensures that the mammalian kinomes available from UniProtKB/Swiss-Prot are of a consistently high standard with each separate entry acting both as a valuable information resource and a central portal to a wealth of further detail via extensive cross-referencing.

Characterization of cyclin L1 and L2 interactions with CDK11 and splicing factors: influence of cyclin L isoforms on splice site selection

Although it has been reported that cyclin L1alpha and L2alpha proteins interact with CDK11(p110), the nature of the cyclin L transcripts, the formation of complexes between the five cyclin L and the three CDK11 protein isoforms, and the influence of these complexes on splicing have not been thoroughly investigated. Here we report that cyclin L1 and L2 genes generate 14 mRNA variants encoding six cyclin L proteins, one of which has not been described previously. Using cyclin L gene-specific antibodies, we demonstrate expression of multiple endogenous cyclin L proteins in human cell lines and mouse tissues. Moreover, we characterize interactions between CDK11(p110), mitosis-specific CDK11(p58), and apoptosis-specific CDK11(p46) with both cyclin Lalpha and -beta proteins and the co-elution of these proteins following size exclusion chromatography. We further establish that CDK11(p110) and associated cyclin Lalpha/beta proteins localize to splicing factor compartments and nucleoplasm and interact with serine/arginine-rich proteins. Importantly, we also determine the effect of CDK11-cyclin L complexes on pre-mRNA splicing. Preincubation of nuclear extracts with purified cyclin Lalpha and -beta isoforms depletes the extract of in vitro splicing activity. Ectopic expression of cyclin L1alpha, L1beta, L2alpha, or L2beta or active CDK11(p110) individually enhances intracellular intron splicing activity, whereas expression of CDK11(p58/p46) or kinase-dead CDK11(p110)represses splicing activity. Finally, we demonstrate that expression of cyclins Lalpha and -beta and CDK11(p110) strongly and differentially affects alternative splicing in vivo. Together, these data establish that CDK11(p110) interacts physically and functionally with cyclin Lalpha and -beta isoforms and SR proteins to regulate splicing.

Genetic variations of the CDC2L2 gene are associated with type 2 diabetes in a Han Chinese cohort

OBJECTIVE

The purpose of the present study was to study the potential association of CDC2L2 variations with type 2 diabetes (T2D).

METHODS

SNPs (single nucleotide polymorphisms) were extensively screened across the CDC2L2 gene by the site-specific PCR method ARMS (Amplification Refractory Mutation System). The identified novel polymorphisms were further evaluated in a Han Chinese cohort comprising of 467 patients with diabetes and 569 nondiabetic controls. In addition, 76 parent-offspring trios were also included in this association study. The case-control and TDT/sibTDT studies are applied for association analysis in this study.

RESULTS

Seven loci (rs1059831, SNP33, rs7528782, SNP11, SNP36, rs11488590 and SNP30) were shown to be significantly associated with T2D in unrelated individuals (p < 0.05). When individuals were stratified by age, sex and body mass index (BMI), the SNP11 was shown to be strongly associated with female patients with T2D, patients whose age was over 45 years and individuals whose BMI was less than 23 (p = 0.018, 0.011 and 0.0089, respectively). However, it was not replicated in the family-based TDT/sibTDT analysis (p = 0.085, OR = 0.63 (CI 95% 0.34-1.06)).

CONCLUSION

Our data suggested that the CDC2L2 gene may contribute to the susceptibility of type 2 diabetes in the northern Han Chinese population, but further studies are needed to replicate these findings.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Novel noncoding RNA from human Y distal heterochromatic block (Yq12) generates testis-specific chimeric CDC2L2

The human Y chromosome, because it is enriched in repetitive DNA, has been very intractable to genetic and molecular analyses. There is no previous evidence for developmental stage- and testis-specific transcription from the male-specific region of the Y (MSY). Here, we present evidence for the first time for a developmental stage- and testis-specific transcription from MSY distal heterochromatic block. We isolated two novel RNAs, which localize to Yq12 in multiple copies, show testis-specific expression, and lack active X-homologs. Experimental evidence shows that one of the above Yq12 noncoding RNAs (ncRNAs) trans-splices with CDC2L2 mRNA from chromosome 1p36.3 locus to generate a testis-specific chimeric beta sv13 isoform. This 67-nt 5'UTR provided by the Yq12 transcript contains within it a Y box protein-binding CCAAT motif, indicating translational regulation of the beta sv13 isoform in testis. This is also the first report of trans-splicing between a Y chromosomal and an autosomal transcript.

Uptake, cellular distribution and novel cellular binding proteins of immunostimulatory CpG oligodeoxynucleotides in glioblastoma cells

Glioblastomas are the most malignant and most frequent brain tumors and exciting targets of gene and immunotherapy. Despite rapid development of experimental therapy little is known about the cellular behaviour of therapeutic oligodeoxynucleotides (ODNs). Here we designed uptake, cellular distribution and cellular binding proteins of immunostimulatory CpG-ODNs in glioblastoma cells by flow cytometry, fluorescence microscopy and mass spectrometry. Our data show that the phosphorothioate (PS) CpG-ODNs uptake in T98G and C6 cells is dose-, time-, temperature-dependent and independent of the CpG dinucleotides. Uptake can be inhibited by sodium azide, polyanions but not by chloroquine. After internalisation FITC labelled CpG-ODNs showed a spotted distribution in cytoplasm. Dozens of cellular binding proteins were identified using mass spectrometry. The binding of ODNs to proteins is dependent on modification and sequence but independent on CpG motif. ODNs bind to cellular proteins that are important for RNA processing and transport. Furthermore, three novel membrane proteins were identified, which might contribute to uptake of ODNs. ODNs binding to these proteins might interfere with the physiological function and thus might cause unwanted effects. Such binding also might influence the uptake efficiency or cellular distribution of therapeutic ODNs.

Comparative genomic analysis of human and chimpanzee proteases

Proteolytic enzymes are implicated in multiple physiological and pathological processes. The availability of the sequence of the chimpanzee genome has allowed us to determine that the chimpanzee degradome-the repertoire of protease genes from this organism-is composed of at least 559 protease and protease-like genes and is virtually identical to that of human, containing 561 genes. Despite the high degree of conservation between both genomes, we have identified important differences that vary from deletion of whole genes to small insertion/deletion events or single nucleotide changes that lead to the specific gene inactivation in one species, mostly affecting immune system genes. For example, the genes encoding PRSS33/EOS, a macrophage serine protease conserved in most mammals, and GGTLA1 are absent in chimpanzee, while the gene for metalloprotease MMP23A, located in chromosome 1p36, has been specifically duplicated in the human genome together with its neighbor gene CDC2L1. Other differences arise from single nucleotide changes in protease genes, such as NAPSB and CASP12, resulting in the presence of functional genes in chimpanzee and pseudogenes in human. Finally, we have confirmed that the Trypanosoma lytic factor HPR is inactive in chimpanzee, likely contributing to the susceptibility of chimpanzees to T. brucei infection. This study provides the first analysis of the chimpanzee degradome and might contribute to the understanding of the molecular bases underlying variations in host defense mechanisms between human and chimpanzee.

Distinct transcriptional profiles characterize oral epithelium-microbiota interactions

Transcriptional profiling, bioinformatics, statistical and ontology tools were used to uncover and dissect genes and pathways of human gingival epithelial cells that are modulated upon interaction with the periodontal pathogens Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. Consistent with their biological and clinical differences, the common core transcriptional response of epithelial cells to both organisms was very limited, and organism-specific responses predominated. A large number of differentially regulated genes linked to the P53 apoptotic network were found with both organisms, which was consistent with the pro-apoptotic phenotype observed with A. actinomycetemcomitans and anti-apoptotic phenotype of P. gingivalis. Furthermore, with A. actinomycetemcomitans, the induction of apoptosis did not appear to be Fas- or TNF(alpha)-mediated. Linkage of specific bacterial components to host pathways and networks provided additional insight into the pathogenic process. Comparison of the transcriptional responses of epithelial cells challenged with parental P. gingivalis or with a mutant of P. gingivalis deficient in production of major fimbriae, which are required for optimal invasion, showed major expression differences that reverberated throughout the host cell transcriptome. In contrast, gene ORF859 in A. actinomycetemcomitans, which may play a role in intracellular homeostasis, had a more subtle effect on the transcriptome. These studies help unravel the complex and dynamic interactions between host epithelial cells and endogenous bacteria that can cause opportunistic infections.

The cyclin-dependent kinase 11 interacts with 14-3-3 proteins

Cyclin-dependent kinase 11 isoforms (CDK11) are members of the p34(cdc2) superfamily. They have been shown to play a role in RNA processing and apoptosis. In the present study, we investigate whether CDK11 interacts with 14-3-3 proteins. Our study shows that the putative 14-3-3 binding site (113-RHRSHS-118) within the N-terminal domain of CDK11(p110) is functional. Endogenous CDK11(p110) binds directly to 14-3-3 proteins and phosphorylation of the serine 118 within the RHRSHS motif seems to be required for the binding. Besides, CDK11(p110) is capable of interacting with several different isoforms of 14-3-3 proteins both in vitro and in vivo. The interaction of 14-3-3 gamma with CDK11(p110) occurs throughout the entire cell cycle and reaches maximum at the G2/M phase. Interestingly, 14-3-3 gamma shows strong interaction with N-terminal portion of caspase-cleaved CDK11(p110) (CDK11(p60)) product at 48 h after Fas treatment, which correlates with the maximal cleavage level of CDK11(p110) and the maximum activation level of CDK11 kinase activity during apoptosis. Collectively, these results suggest that CDK11 kinases could be regulated by interaction with 14-3-3 proteins during cell cycle and apoptosis.

Downregulation of beta1,4-galactosyltransferase 1 inhibits CDK11(p58)-mediated apoptosis induced by cycloheximide

Cyclin-dependent kinase 11 (CDK11; also named PITSLRE) is part of the large family of p34(cdc2)-related kinases whose functions appear to be linked with cell cycle progression, tumorigenesis, and apoptotic signaling. The mechanism that CDK11(p58) induces apoptosis is not clear. Some evidences suggested beta1,4-galactosyltransferase 1 (beta1,4-GT 1) might participate in apoptosis induced by CDK11(p58). In this study, we demonstrated that ectopically expressed beta1,4-GT 1 increased CDK11(p58)-mediated apoptosis induced by cycloheximide (CHX). In contrast, RNAi-mediated knockdown of beta1,4-GT 1 effectively inhibited apoptosis induced by CHX in CDK11(p58)-overexpressing cells. For example, the cell morphological and nuclear changes were reduced; the loss of cell viability was prevented and the number of cells in sub-G1 phase was decreased. Knock down of beta1,4-GT 1 also inhibited the release of cytochrome c from mitochondria and caspase-3 processing. Therefore, the cleavage of CDK11(p58) by caspase-3 was reduced. We proposed that beta1,4-GT 1 might contribute to the pro-apoptotic effect of CDK11(p58). This may represent a new mechanism of beta1,4-GT 1 in CHX-induced apoptosis of CDK11(p58)-overexpressing cells.

Isolation and characterization of the human Cdc2L1 gene promoter

CDK11 (cyclin-dependent kinase 11, formerly known as PITSLRE) is a member of the p34cdc2-related kinases. It has been previously shown to be involved in a variety of different cellular processes including RNA processing, apoptosis, and cell cycle progression. It is encoded by two different but highly similar genes, Cdc2L1 (cell division control 2 like 1) and Cdc2L2 (cell division control 2 like 2). Previous studies from our group identified and characterized the transcriptional regulation of the human Cdc2L2 gene promoter. The current studies identify and characterize the Cdc2L1 gene promoter. We cloned the promoter and elucidated the different transcriptional regulatory elements that reside within the 5' region of the gene. Deletion analysis of the promoter showed a region of nucleotides -152 to +11 to be necessary for basal transcription of the Cdc2L1 gene. Sequencing analysis found this region of the promoter to be highly GC-rich but is lacking both TATA and CAAT boxes. There are several different transcription factor binding sites that are consensus or near consensus found within this region. The potential binding sites include two Ets-1 sites, one Skn-1 site, and one E2F-1 site. Transfection studies of various site-directed mutagenesis clones for these different sites revealed that both Ets-1 sites play critical roles in sustained transcriptional activity as well as Skn-1. Chromatin immunoprecipitation of the endogenous promoter with Ets-1 and Skn-1 verified an in vivo association of Ets-1 and Skn-1 transcription factors with the endogenous promoter. These results, in addition to our Cdc2L2 results, lead to the further comprehension of the fundamental mechanisms dictating CDK11 gene expression through the Cdc2L1 gene promoter.

EGFR-induced cell migration is mediated predominantly by the JAK-STAT pathway in primary esophageal keratinocytes

The epidermal growth factor receptor (EGFR) activates several signaling cascades in response to epidermal growth factor stimulation. One of these signaling events involves tyrosine phosphorylation of signal transducer and activator of transcription (STAT), whereas another involves activation of the phosphatidylinositol 3-OH kinase pathway. Two possibilities for STAT activation exist: a janus kinase (JAK)-dependent and a JAK-independent mechanism. Herein, we demonstrate that EGFR overexpression in primary esophageal keratinocytes activates STAT in a JAK-dependent fashion with the functional consequence of enhanced cell migration, which can be abolished by use of a JAK-specific inhibitor, AG-490. We determined the mechanisms underlying the signal transduction pathway responsible for increased cell migration. Stimulation of EGFR induces Tyr701 phosphorylation of STAT1 and initiates complex formation of STAT1 and STAT3 with JAK1 and JAK2. Thereafter, the STATs translocate to the nucleus within 15 min. In addition, we found that activation of this signaling pathway results in matrix metalloproteinase-1 (MMP-1) activity. By contrast, Akt activation does not impact the EGFR-STATs-JAKs complex formation and nuclear translocation of the STATs with subsequent MMP-1 activity, although Akt activation may contribute to cell migration through an independent mechanism. Taken together, we find that the recruitment of the STAT-JAK complex by EGFR is responsible for keratinocyte migration that, in turn, might be mediated by MMP-1 activation.

Perioperative diagnosis of cystosarcoma phyllodes of the breast may be enhanced by MIB-1 index

BACKGROUND

The recurring theme in cystosarcoma phyllodes (CSP) is one of underdiagnosis by pathologists and undertreatment by surgeons. Major areas of investigation relating to the diagnosis of CSP center on accurate preoperative diagnosis, elucidating the relevance of histological classification with respect to outcome, and identifying novel markers to reliably differentiate CSP from fibroadenoma (FA).

MATERIALS AND METHODS

Fifteen CSP and 7 cellular FA controls (where the preoperative diagnosis was unclear) were retrospectively investigated. Preoperative histological and radiological investigations were reviewed for efficacy. The ability of MIB-1 antibody to differentiate the two fibroepithelial lesions was investigated using immunohistochemical estimation of the MIB-1 index.

RESULTS AND DISCUSSION

Preoperative core biopsy had a sensitivity of 75% but was carried out in only 23% of cases. Fine needle aspiration cytology and radiological assessment were not efficacious in preoperative diagnosis. Proliferative activity (MIB-1 indices) was significantly higher in CSP than in a selected population of FA where there was preoperative diagnostic uncertainty (P < 0.0001). Indices were also able to determine CSP subclassification. This suggests MIB-1 as a constructive adjunctive investigation when evaluating histological features to differentiate CSP from FA in difficult cases.

CONCLUSIONS

The use of MIB-1 may increase the sensitivity of preoperative core biopsy diagnosis, offering more effective surgical planning and decreasing immediate reoperation rates.

Identification and characterization of the human Cdc2l2 gene promoter

The CDK11 (cyclin-dependent kinase 11, formerly known as PITSLRE) protein kinases are part of the large family of p34(cdc2)-related kinases and have been shown to play a role in cell cycle progression, RNA processing and apoptosis. They are encoded by two genes-cell division control like 1 (Cdc2L1) and cell division control like 2 (Cdc2L2). To date, little is known about the transcription factors controlling their expression. To understand the mechanisms underlying the regulation of CDK11 gene expression, we cloned and identified the Cdc2L2 promoter and determined its transcriptional regulatory elements. By deletion analysis, a region between nucleotides -145 and +10 was identified to be critical for basal level transcription of the Cdc2L2 gene. Sequencing analysis revealed that the proximal promoter of the Cdc2L2 gene is GC rich and does not contain TATA and CAAT boxes. However, multiple consensus and near consensus transcription factor binding sites were found to be present in this region, such as two Ets-1, one cAMP-responsive element (CRE) and one TCF11/LCR-F1/Nrf1 binding sites. Site-directed mutagenesis and transfection studies revealed that all these binding sites were necessary to achieve sustained transcriptional activity. Electrophoretic mobility shift assay confirmed that transcription factors Ets-1 and CREB bind to the Cdc2L2 promoter elements, indicating their potential role in the transcriptional regulation of Cdc2L2 gene. More importantly, Ets-1, CREB and phosphorylated CREB were found binding to the endogenous Cdc2L2 promoter using chromatin immunoprecipitation (CHIP) assay. Our results provide the foundation for further studies into the regulation of Cdc2L2 gene expression in normal homeostasis and cancer.

Death receptor 3 (DR3) gene duplication in a chromosome region 1p36.3: gene duplication is more prevalent in rheumatoid arthritis

The death receptor 3 (DR3) gene is a member of the apoptosis-inducing Fas gene family. In the current study, fluorescence in situ hybridization (FISH) and Fiber-FISH revealed the existence of a second DR3 gene approximately 200 kb upstream of the original DR3 gene. The existence of the duplicated DR3 gene was confirmed by sequencing the corresponding human artificial chromosome clones as well as with quantitative PCR that measured the ratio of the DR3 gene mutation (Rm), intrinsic to rheumatoid arthritis (RA) patients, by simultaneous amplification of the normal and mutated DR3 sequences. The DR3 gene duplication measured by FISH was found to be more frequent in patients with RA as compared to healthy individuals. We therefore surmise that the human DR3 gene can be duplicated and that this gene duplication is more prevalent in patients with RA.

Failure to proliferate and mitotic arrest of CDK11(p110/p58)-null mutant mice at the blastocyst stage of embryonic cell development

The CDK11(p110) protein kinases are part of large-molecular-weight complexes that also contain RNA polymerase II, transcriptional elongation factors, and general pre-mRNA splicing factors. CDK11(p110) isoforms may therefore couple transcription and pre-mRNA splicing by their effect(s) on certain proteins required for these processes. The CDK11(p58) kinase isoform is generated from the CDK11(p110) mRNA through the use of an internal ribosome entry site in a mitosis-specific manner, suggesting that this kinase may regulate the cell cycle during mitosis. The in vivo role and necessity of CDK11(p110/p58) kinase function during mammalian development were examined by generating CDK11(p110/p58)-null mice through targeted disruption of the corresponding gene using homologous recombination. While heterozygous mice develop normally, disruption of both CDK11(p110/p58) alleles results in early embryonic lethality due to apoptosis of the blastocyst cells between 3.5 and 4 days postcoitus. Cells within these embryos exhibit both proliferative defect(s) and a mitotic arrest. These results are consistent with the proposed cellular functions of the CDK11(p110/p58) kinases and confirm that the CDK11(p110/p58) kinases are essential for cellular viability as well as normal early embryonic development.

A genomic analysis of rat proteases and protease inhibitors

Proteases perform important roles in multiple biological and pathological processes. The availability of the rat genome sequence has facilitated the analysis of the complete protease repertoire or degradome of this model organism. The rat degradome consists of at least 626 proteases and homologs, which are distributed into 24 aspartic, 160 cysteine, 192 metallo, 221 serine, and 29 threonine proteases. This distribution is similar to that of the mouse degradome but is more complex than that of the human degradome composed of 561 proteases and homologs. This increased complexity of rat proteases mainly derives from the expansion of several families, including placental cathepsins, testases, kallikreins, and hematopoietic serine proteases, involved in reproductive or immunological functions. These protease families have also evolved differently in rat and mouse and may contribute to explain some functional differences between these closely related species. Likewise, genomic analysis of rat protease inhibitors has shown some differences with mouse protease inhibitors and the expansion of families of cysteine and serine protease inhibitors in rodents with respect to human. These comparative analyses may provide new views on the functional diversity of proteases and inhibitors and contribute to the development of innovative strategies for treating proteolysis diseases.

Characterization of cyclin L2, a novel cyclin with an arginine/serine-rich domain: phosphorylation by DYRK1A and colocalization with splicing factors

A novel method employing filter arrays of a cDNA expression library for the identification of substrates for protein kinases was developed. With this technique, we identified a new member of the cyclin family, cyclin L2, as a substrate of the nuclear protein kinase DYRK1A. Cyclin L2 contains an N-terminal cyclin domain and a C-terminal arginine/serine-rich domain (RS domain), which is a hallmark of many proteins involved in pre-mRNA processing. The gene for cyclin L2 encodes the full-length cyclin L2, which is predominantly expressed in testis, as well as a truncated splicing variant (cyclin L2S) that lacks the RS domain and is ubiquitously expressed in human tissues. Full-length cyclin L2, but not cyclin L2S, was associated with the cyclin-dependent kinase PITSLRE. Cyclin L2 interacted with splicing factor 2 in vitro and was co-localized with the splicing factor SC35 in the nuclear speckle compartment. Photobleaching experiments showed that a fusion protein of green fluorescent protein and cyclin L2 in nuclear speckles rapidly exchanged with unbleached molecules in the nucleus, similar to other RS domain-containing proteins. In striking contrast, the closely related green fluorescent protein-cyclin L1 was immobile in the speckle compartment. DYRK1A interacted with cyclin L2 in pull-down assays, and overexpression of DYRK1A stimulated phosphorylation of cyclin L2 in COS-7 cells. These data characterize cyclin L2 as a highly mobile component of nuclear speckles and suggest that DYRK1A may regulate splicing by phosphorylation of cyclin L2.

The cyclin-dependent kinase 11p46 isoform interacts with RanBPM

We identified Ran-binding protein (RanBPM) as an interacting partner of the caspase-processed C-terminal domain of cyclin-dependent kinase 11 (CDK11(p46)) by using the yeast two-hybrid system. CDK11(p110) protein kinases are members of the cyclin-dependent kinase superfamily. During staurosporine-, Fas-, and tumor necrosis factor alpha-induced apoptosis caspase-processed activated CDK11(p46) is generated from larger CDK11(p110) isoforms. CDK11(p46) promotes apoptosis when it is ectopically expressed in human cells. However, the mechanism of signal transduction through CDK11(p46) is still unclear. In this study, we demonstrate that CDK11(p46) directly interacts with RanBPM in vitro and in human cells. RanBPM contains a conserved SPRY (repeats in splA and Ryr) domain and is localized both in the nucleus and cytoplasm. The SPRY domain of RanBPM is responsible for the association between CDK11(p46) and RanBPM. Furthermore, we show that CDK11(46) phosphorylates RanBPM.

The C-terminal kinase domain of the p34cdc2-related PITSLRE protein kinase (p110C) associates with p21-activated kinase 1 and inhibits its activity during anoikis

The PITSLRE protein kinases are parts of the large family of p34cdc2-related kinases. During apoptosis induced by some stimuli, specific PITSLRE isoforms are cleaved by caspase to produce a protein that contains the C-terminal kinase domain of the PITSLRE proteins (p110C). The p110C induces apoptosis when it is ectopically expressed in Chinese hamster ovary cells. In our study, similar induction of this p110C was observed during anoikis in NIH3T3 cells. To investigate the molecular mechanism of apoptosis mediated by p110C, we used the yeast two-hybrid system to screen a human fetal liver cDNA library and identified p21-activated kinase 1 (PAK1) as an interacting partner of p110C. The association of p110C with PAK1 was further confirmed by in vitro binding assay, in vivo coimmunoprecipitation, and confocal microscope analysis. The interaction of p110C with PAK1 occurred within the residues 210-332 of PAK1. Neither association between p58PITSLRE or p110PITSLRE and PAK1 nor association between p110C and PAK2 or PAK3 was observed. Anoikis was increased and PAK1 activity was inhibited when NIH3T3 cells were transfected with p110C. Furthermore, the binding of p110C with PAK1 and inhibition of PAK1 activity were also observed during anoikis. Taken together, these data suggested that PAK1 might participate in the apoptotic pathway mediated by p110C.

CDK11 complexes promote pre-mRNA splicing

The PITSLRE protein kinases, hereafter referred to as CDK11 because of their association with the cyclin L regulatory partner, belong to large molecular weight protein complexes that contain RNA polymerase II. These CDK11(p110) complexes have been reported to influence transcription as well as interact with the general pre-mRNA-splicing factor RNPS1. Some of these complexes may also play a role in pre-mRNA splicing. Using a two-hybrid interactive screen, the splicing protein 9G8 was identified as an in vivo partner for CDK11(p110). The identification of several splicing-related factors as CDK11(p110) interactors along with the close relationship between transcription and splicing indicated that CDK11(p110) might influence splicing activity directly. Immunodepletion of CDK11(p110) from splicing extracts greatly reduced the appearance of spliced products using an in vitro assay system. Moreover, the re-addition of these CDK11(p110) immune complexes to the CDK11(p110)-immunodepleted splicing reactions completely restored splicing activity. Similarly, the addition of purified CDK11(p110) amino-terminal domain protein was sufficient to inhibit the splicing reaction. Finally, 9G8 is a phosphoprotein in vivo and is a substrate for CDK11(p110) phosphorylation in vitro. These data are among the first demonstrations showing that a CDK activity is functionally coupled to the regulation of pre-mRNA-splicing events and further support the hypothesis that CDK11(p110) is in a signaling pathway that may help to coordinate transcription and RNA-processing events.

Matrix metalloproteinases: old dogs with new tricks

The matrix metalloproteinase family in humans comprises 23 enzymes, which are involved in many biological processes and diseases. It was previously thought that these enzymes acted only to degrade components of the extracellular matrix, but this view has changed with the discovery that non-extracellular-matrix molecules are also substrates.

MMPs and TIMPs--an historical perspective

There are currently 25 known vertebrate matrix metalloproteinases (MMPs) and 4 tissue inhibitors of metalloproteinases (TIMPs). This article reviews these proteases from an historical perspective in terms of who discovered each protein, when the sequence was established, when action on protein substrates was demonstrated, and what names have been used. A similar approach is taken for the TIMPS, and their multiple functions in addition to protease inhibition are emphasized. MMPs from invertebrates, plants, and bacteria are also discussed. This review is an outgrowth and update of a chapter by the same name originally published in Matrix Metalloproteinase Protocols, pp. 1-23, edited by I. M. Clark and published by Humana Press in 2001.

Analysis of mutations and identification of several polymorphisms in the putative promoter region of the P34CDC2-related CDC2L1 gene located at 1P36 in melanoma cell lines and melanoma families

Chromosome 1 abnormalities are the most commonly detected aberrations in many cancers including malignant melanoma. Partial deletions and an allelic loss of the chromosome 1p36 region observed in melanoma indicate the presence of putative tumor suppressor gene(s) in this region. A candidate gene, CDC2L1, which encodes PITSLRE proteins related to p34(cdc2), is mapped to 1p36. To determine whether CDC2L1 mutation is involved in melanoma development, we examined 20 melanoma cell lines and 11 members of melanoma-prone families linked to chromosome 1p36. Mutation analysis throughout the entire coding region of the CDC2L1 gene revealed only 1 mutation (C-->T at nucleotide location 97 of exon 7, Ser-->Leu) in the melanoma cell line UACC 903 out of 20 melanoma cell lines and 6 melanoma cases. However, 4 polymorphic nucleotide changes, C-48T, G-53C, T-103C and T-210C, in the putative promoter region of CDC2L1 were identified. The 4 variants were located within or beside the conserved binding sites of transcription factors TCF11, MZF1 and TAAC box, indicating their potential effects on the regulation of CDC2L1 expression. No aberrant methylation of the CDC2L1 CpG island in the promoter region was observed by sodium bisulfite genomic sequencing. These results indicate that mutations are rare in the CDC2L1 gene in these melanoma cell lines and melanoma families and that the aberrant cytosine methylation of the CDC2L1 CpG island is not the mechanism of CDC2L1 repression in melanoma. The contribution of 4 promoter polymorphisms to the transcriptional regulation of the gene and its association with melanoma warrants further investigation.

New functions for the matrix metalloproteinases in cancer progression

Matrix metalloproteinases (MMPs) have long been associated with cancer-cell invasion and metastasis. This provided the rationale for clinical trials of MMP inhibitors, unfortunately with disappointing results. We now know, however, that the MMPs have functions other than promotion of invasion, have substrates other than components of the extracellular matrix, and that they function before invasion in the development of cancer. With this knowledge in hand, can we rethink the use of MMP inhibitors in the clinic?

PITSLRE p110 protein kinases associate with transcription complexes and affect their activity

Although the PITSLRE protein kinases are members of the cyclin-dependent kinase superfamily, their cellular function is unclear. Previously we demonstrated that the general RNA splicing factor RNPS1 is a specific PITSLRE p110 kinase interactor in vivo. This suggests that the PITSLRE family of protein kinases is involved in some aspect of RNA processing or transcription. Here we identify multiple transcriptional elongation factors, including ELL2, TFIIF(1), TFIIS, and FACT, as PITSLRE kinase-associated proteins. We demonstrate that PITSLRE p110 protein kinases co-immunoprecipitate and/or co-purify with these elongation factors as well as with RNA polymerase II. Antibody-mediated inhibition of PITSLRE kinase specifically suppressed RNA polymerase II-dependent in vitro transcription initiated at a GC-rich (adenosine deaminase) or TATA box-dependent (Ad2ML) promoter, and this suppression was rescued by readdition of purified PITSLRE p110 kinase. Together, these data strongly suggest that PITSLRE protein kinases participate in a signaling pathway that potentially regulates or links transcription and RNA processing events.

Tandem duplication. A novel type of triplet repeat instability

Triplet repeat sequence (TRS) inserts containing (CTG.CAG)(n) (17-175 units in length) were tandemly duplicated when propagated in plasmids in Escherichia coli. The products of this novel type of TRS genetic instability are tracts of as many as 34 multiple units, which contain the entire TRS as well as 129 base pairs of nonrepetitive flanking sequence. The duplication process required the presence of two or more TRS-containing units. Close proximity (170 base pairs) of the TRS to the R6K gamma origin of replication of the pUTminiTn5Cm-derived constructs stimulated the tandem duplication process. These events are proposed to occur due to secondary structure formation, stalling of DNA synthesis, and slippage-mediated misalignment of the complementary strands relative to each other during DNA replication. This mechanism may account for the TRS-associated duplications in protein kinase and metalloprotease genes in neuroblastomas and melanomas, as well as the massive repeat expansions in type II triplet repeat neurological diseases.

Caspase 8 is deleted or silenced preferentially in childhood neuroblastomas with amplification of MYCN

Caspase 8 is a cysteine protease regulated in both a death-receptor-dependent and -independent manner during apoptosis. Here, we report that the gene for caspase 8 is frequently inactivated in neuroblastoma, a childhood tumor of the peripheral nervous system. The gene is silenced through DNA methylation as well as through gene deletion. Complete inactivation of CASP8 occurred almost exclusively in neuroblastomas with amplification of the oncogene MYCN. Caspase 8-null neuroblastoma cells were resistant to death receptor- and doxorubicin-mediated apoptosis, deficits that were corrected by programmed expression of the enzyme. Thus, caspase 8 acts as a tumor suppressor in neuroblastomas with amplification of MYCN.

Identification and characterization of a novel cell cycle-regulated internal ribosome entry site

PITSLRE protein kinases are related to the large family of cyclin-dependent kinases. They have been proposed to act as tumor suppressor genes and have been shown to play a role in cell cycle progression. We report that two PITSLRE protein kinase isoforms, namely p11O(PITSLRE) and p58(PITSLRE), are translated from a single transcript by initiation at alternative in-frame AUG codons. p110(PITSLRE) is produced by classical cap-dependent translation, whereas p58(PITSLRE) results from internal initiation of translation controlled by an internal ribosome entry site (IRES) with unique properties. The IRES element is localized to the mRNA coding region, and its activity is cell cycle regulated, which permits translation of p58(PITSLRE) in G2/M.

CA-MMP: a matrix metalloproteinase with a novel cysteine array, but without the classic cysteine switch

A matrix metalloproteinase (MMP)-like gene was identified in mouse to contain a conserved MMP catalytic domain and an RRRR motif. It lacks a classic cysteine switch, but it possesses two novel motifs: a cysteine array (Cys-X(6)-Cys-X(8)-Cys-X(10)-Cys-X(3)-Cys-X(2)-Cys), and a novel Ig-fold. It is named CA-MMP after the distinct cysteine array motif, and little is known about its biochemical function. In an attempt to characterize CA-MMP activity, the full-length sequence was expressed in mammalian cells and its product found to be cell-associated without detectable secretion. In light of this unusual finding, a chimera combining the catalytic domain of CA-MMP with the prodomain of stromelysin-3 was constructed to express a fully active enzyme in mammalian cells. Purified CA-MMP catalytic domain expresses proteolytic activity against protein substrates in an MMP inhibitor sensitive fashion. Taken together, it is concluded that CA-MMP is an MMP with distinct structure, biochemical properties and evolutionary history that may define a new subclass of the MMP superfamily.