Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human T-cell lymphotropic virus type 1 (HTLV-1) is associated with adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). T-cell transformation is mainly due to the actions of the viral phosphoprotein Tax. Tax interacts with multiple transcriptional factors, aiding the transcription of many cellular genes. Here, we report that the cyclin-dependent kinase inhibitor p21/waf1 is overexpressed in all HTLV-1-infected cell lines tested as well as in ATL and HAM/TSP patient samples. Tax was found to be able to transactivate the endogenous p21/waf1 promoter, as detected by RNase protection, as well as activate a series of wild-type and 5'-deletion constructs linked to a luciferase reporter cassette. Wild-type but not a mutant form of Tax (M47) transactivated the p21/waf1 promoter in a p53-independent manner and utilized a minimal promoter that contained E2A and TATA box sequences. The p21/waf1 protein was reproducibly observed to be complexed with cyclin A/cdk2 and not with any other known G(1), S, or G(2)/M cyclins. Functionally, the association of p21/cyclin A/cdk2 decreased histone H1 phosphorylation in vitro, as observed in immunoprecipitations followed by kinase assays, and affected other substrates, such as the C terminus of Rb protein involved in c-Abl and histone deacetylase-1 (HDAC1) regulation. Interestingly, upon the use of a stress signal, such as gamma-irradiation, we found that the p21/cyclin A/cdk2 complex was able to block all known phosphorylation sites on the Rb molecule. Finally, using elutriated cell cycle fractions and a stress signal, we observed that the HTLV-1-infected T cells containing wild-type Tax, which had been in early or mid-G(1) phase prior to gamma-irradiation, arrested in G(1) and did not undergo apoptosis. This may be an important mechanism for an oncogenic virus such as HTLV-1 to stop the host at the G(1)/S boundary and to repair the damaged DNA upon injury, prior to S-phase entry.
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PMID:Overexpression of p21(waf1) in human T-cell lymphotropic virus type 1-infected cells and its association with cyclin A/cdk2. 1090 81

By utilizing a human cDNA expression array blot (588 genes), we have observed overexpression of various transcription factors, cell cycle regulated kinases, and DNA repair genes in HTLV-1-infected T cells. One of the genes of interest, and focus in this study, is the cyclin-dependent kinase inhibitor, p21/waf1. The p21/waf1 transcription and protein is overexpressed in all HTLV-1-infected cell lines tested as well as ATL and HAM/TSP patient samples. While p21/waf1 has been shown to display a selectivity for G(1)/S cyclin/cdk complexes, we have observed p21/waf1 to be complexed with cyclin A/cdk2. Functionally, the association of p21/cyclin A/cdk2 decreased the histone H1 phosphorylation in vitro, as observed in immunoprecipitations followed by kinase assays, as well as affecting other substrates such as the C-terminus of Rb protein involved in c-Abl and HDAC1 regulation. Wild-type, but not a mutant form (M47) of Tax, was found to be able to transactivate the p21/waf1 promoter in a p53-independent manner. We found that the minimal p21/waf1 promoter (-49 to +49 sequence) was activated by Tax and the minimal promoter contained two E2A transcription factor binding sites located between the TATA box and the initiation site. E2A proteins, E12 and E47, as well as a related helix-loop-helix protein, HEB, are all up-regulated in HTLV-1-infected T cells. When using band shift analysis, we found that only the E1 site (overlapping the transcription start site) was a functional DNA binding site. By using a chromatin immunoprecipitation (ChIP) assay, we observed that histone H4, and not histone H3, was acetylated from the endogenous p21/waf1 promoter in vivo, implying that CBP/p300, and not the SAGA complex, was critical in complexing with E2A in up-regulation of p21/waf1 in HTLV-1-infected cells.
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PMID:Gene expression array of HTLV type 1-infected T cells: Up-regulation of transcription factors and cell cycle genes. 1108 Aug 12

HTLV-1 is the etiologic agent for adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), where viral replication and transformation are largely dependent upon modification of regulatory and host cell cycle proteins. The mechanism of HTLV-1 transformation appears to be distinct from that of many known chronic or acute leukemia viruses and is related to the viral activator Tax. Here we show that cyclin E, can associate tightly with the coactivator p300 and Pol II complex in HTLV-1 infected cells. The cyclin E associated complex is kinase active and phosphorylates the carboxy terminal domain of RNA Pol II. More importantly, p21/Waf1, a well-known cdk inhibitor at the G1/S border, inhibits transcription of HTLV-1 in both transfections and in in vitro transcription assays. Finally, specific cdk chemical inhibitors, functionally similar to cellular cdkIs, such as p21/Waf1 which inhibits cyclin E/cdk2 activity, also inhibit transcription of the HTLV-1 promoter. In particular, Purvalanol A, with an IC50 of 0.035 microm inhibits activated, but not basal transcription, as well as HTLV-1 infected cells. Collectively, the role of cyclin E/cdk2 in HTLV-1 infected cells and its involvement in RNA Pol II phosphorylation is discussed.
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PMID:Inhibition of HTLV-1 transcription by cyclin dependent kinase inhibitors. 1223 81

Thrombospondin-1 (TSP1) is an endogenous inhibitor of angiogenesis, which limits blood vessel density in normal tissues and curtails tumor growth. Previous studies of the molecular and cellular effects of TSP1 in angiogenesis have been contradictory. Here, we show that retinal endothelial cells (REC) prepared from TSP1-deficient (TSP1-/-) mice are more proliferative and migratory compared to the wild type REC. We observed up-regulation of the cell cycle regulators, including cyclin A, D1, and Cdk2, as well as the enhanced sequential activities of Src, PI3-kinase, Akt/PKB, Rac1/Cdc42 GTPases, and p38 MAP kinase in TSP1-/- REC. The increased levels of fibronectin and active Akt/PKB were also observed in retinal vasculature of TSP1-/- mice in vivo. Inhibition of Src/PI3-kinase/P38 MAP kinase activities in TSP1-/- REC resulted in decreased migration. Furthermore, TSP1-/- REC showed decreased intracellular levels of active Fyn and JNK2 without affecting caspase-3 activity. Thus, our results demonstrate that in the absence of TSP1, the proangiogenic signaling is enhanced, possibly through up-regulation of fibronectin expression. The enhanced signaling further promotes EC proliferation, migration, and survival. These novel observations support the TSP1's role as an endogenous inhibitor of angiogenesis whose endothelium expression promotes a quiescent, differentiated phenotype.
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PMID:Enhanced proangiogenic signaling in thrombospondin-1-deficient retinal endothelial cells. 1662 39

Human T-cell leukemia virus type-1 (HTLV-1) induces adult T-cell leukemia/lymphoma (ATL/L), a fatal lymphoproliferative disorder, and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic progressive disease of the central nervous system after a long period of latent infection. Although the mechanism of transformation and leukemogenesis is not fully elucidated, there is evidence to suggest that the viral oncoprotein Tax plays a crucial role in these processes through the regulation of several pathways including NF-kappaB and the cell cycle pathways. The observation that NF-kappaB, which is strongly induced by Tax, is indispensable for the maintenance of the malignant phenotype of HTLV-1 by regulating the expression of various genes involved in cell cycle regulation and inhibition of apoptosis provides a possible molecular target for these infected cells. To develop potential new therapeutic strategies for HTLV-1 infected cells, in this present study, we initially screened a battery of NF-kappaB and CDK inhibitors (total of 35 compounds) to examine their effects on the growth and survival of infected T-cell lines. Two drugs namely BMS-345541 and Purvalanol A exhibited higher levels of growth inhibition and apoptosis in infected cell as compared to uninfected cells. BMS-345541 inhibited IKKbeta kinase activity from HTLV-1 infected cells with an IC50 (the 50% of inhibitory concentration) value of 50 nM compared to 500 nM from control cells as measured by in vitro kinase assays. The effects of Purvalanol A were associated with suppression of CDK2/cyclin E complex activity as previously shown by us. Combination of both BMS-345541 and Purvalanol A showed a reduced level of HTLV-1 p19 Gag production in cell culture. The apparent apoptosis in these infected cells were associated with increased caspase-3 activity and PARP cleavage. The potent and selective apoptotic effects of these drugs suggest that both BMS-345541 and Purvalanol A, which target both NF-kappaB and CDK complex and the G1/S border, might be promising new agents in the treatment of these infected patients.
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PMID:Two specific drugs, BMS-345541 and purvalanol A induce apoptosis of HTLV-1 infected cells through inhibition of the NF-kappaB and cell cycle pathways. 1854 67