Cyclin K functions as a CDK9 regulatory subunit and participates in RNA polymerase II transcription

Important progress in the understanding of elongation control by RNA polymerase II (RNAPII) has come from the recent identification of the positive transcription elongation factor b (P-TEFb) and the demonstration that this factor is a protein kinase that phosphorylates the carboxyl-terminal domain (CTD) of the RNAPII largest subunit. The P-TEFb complex isolated from mammalian cells contains a catalytic subunit (CDK9), a cyclin subunit (cyclin T1 or cyclin T2), and additional, yet unidentified, polypeptides of unknown function. To identify additional factors involved in P-TEFb function we performed a yeast two-hybrid screen using CDK9 as bait and found that cyclin K interacts with CDK9 in vivo. Biochemical analyses indicate that cyclin K functions as a regulatory subunit of CDK9. The CDK9-cyclin K complex phosphorylated the CTD of RNAPII and functionally substituted for P-TEFb comprised of CDK9 and cyclin T in in vitro transcription reactions.

Posttransplantation plasmacytic proliferations related to Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV), which was originally detected in Kaposi's sarcoma, also has been found in primary effusion lymphomas (PELs) and some cases of multicentric Castleman's disease. We describe two transplant recipients who developed Kaposi's sarcoma and a spectrum of non-neoplastic lymphoproliferative disorders that show pronounced plasmacytic and plasmacytoid features. The first patient had recurrent pleural effusions and Castleman's disease-like changes in lymph nodes. The second patient had systemic lymphadenopathy and hepatosplenomegaly secondary to diffuse infiltration by polyclonal plasma cells and plasmacytoid B lymphocytes that clinically mimicked Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disease. In both cases, KSHV DNA was detected by polymerase chain reaction and Southern blotting, and KSHV vIL-6 protein expression was identified in affected tissues by immunohistochemical localization. In contrast, no evidence of KSHV coinfection was detected in any of 31 EBV-related posttransplant lymphoproliferative disorders or 112 non-PEL lymphomas tested. The pathologic findings in these two patients were not representative of malignancy by morphologic, immunophenotypic, or molecular criteria. This study underscores the marked propensity for hematolymphoid proliferations associated with KSHV infections to show plasmacytic features. Additionally, this study describes use of an antibody reactive against KSHV vIL-6 that can readily detect a subpopulation of KSHV-infected hematopoietic cells.

Continuous wet granulation using fluidized-bed techniques. I. Examination of powder mixing kinetics and preliminary granulation experiments

The movement of powder/granules within the reaction chambers of two continuously-operating granulators (Niro/Aeromatic-Fielder Contipharm and the Glatt Continuous Fluidized-Bed Granulator) was examined by adding dyestuffs to the powder-inlet. Comparison of the dye mass-fraction in the product with the appropriate transport equation indicated random mixing and transport within the product-chamber. Photographs of powder movement on the gill-plate of the Contipharm showed, however, air-driven transport of powder from inlet to outlet, which evidently does not prevent overall random mixing. The output half-life is > 20 min, showing substantial residence time within each machine. A simplex granule was also prepared using the two machines. With the Niro it was shown that an increase in binder solution spraying rate during the continuous process produced an increase in particle size distribution and moisture content. Reduction of air volumetric flow rate on the Glatt machine during continuous operation produced higher moisture content of the product. It was thus demonstrated that changes in process conditions during continuous operation produce predictable alterations in product properties,

Mesenteric cysts--a series of six cases with a review of the literature

BACKGROUND

Symptomatic mesenteric cysts account for only 1 in 100,000 acute adult and 1 in 20,000 acute paediatric admissions. Acute symptoms are related to compression of intra-abdominal organs or stretching of the mesentery by rapid expansion. An abdominal mass, mobile in transverse but not longitudinal plane, is often the only physical finding.

METHOD

We outline the presentation, management and histological findings of 6 cases that presented to this hospital from 1987-1997.

RESULTS

There were 5 adults aged 32-79 yr and an 8 yr old boy. The child presented acutely with a painful tender abdominal mass. Of the adults, 1 presented acutely, 2 with chronic symptoms and 2 were incidental findings. Mesenteric cysts were successfully resected in all cases.

CONCLUSION

Surgical intervention is recommended and resection of adjacent bowel may be necessary for complete excision. Successful minimal access surgery via the laparoscope has been reported and may become more widely applicable.

Molecular interactions among protein phosphatase 2A, tau, and microtubules. Implications for the regulation of tau phosphorylation and the development of tauopathies

Hyperphosphorylated forms of the neuronal microtubule (MT)-associated protein tau are major components of Alzheimer's disease paired helical filaments. Previously, we reported that ABalphaC, the dominant brain isoform of protein phosphatase 2A (PP2A), is localized on MTs, binds directly to tau, and is a major tau phosphatase in cells. We now describe direct interactions among tau, PP2A, and MTs at the submolecular level. Using tau deletion mutants, we found that ABalphaC binds a domain on tau that is indistinguishable from its MT-binding domain. ABalphaC binds directly to MTs through a site that encompasses its catalytic subunit and is distinct from its binding site for tau, and ABalphaC and tau bind to different domains on MTs. Specific PP2A isoforms bind to MTs with distinct affinities in vitro, and these interactions differentially inhibit the ability of PP2A to dephosphorylate various substrates, including tau and tubulin. Finally, tubulin assembly decreases PP2A activity in vitro, suggesting that PP2A activity can be modulated by MT dynamics in vivo. Taken together, these findings indicate how structural interactions among ABalphaC, tau, and MTs might control the phosphorylation state of tau. Disruption of these normal interactions could contribute significantly to development of tauopathies such as Alzheimer's disease.

Adult glioma in relation to residential power frequency electromagnetic field exposures in the San Francisco Bay area

In a population-based study, we examined residential power frequency electromagnetic field exposures for 492 adults newly diagnosed with histologically confirmed glioma between August 1, 1991 and April 30, 1994, in the San Francisco Bay area and 462 controls, obtained through random-digit dialing frequency, matched to cases for age, gender, and race. Residential exposure assessment consisted of spot measures with EMDEX (Enertech Consultants, Campbell, CA) meters and wire codes based on characterization and location of nearby power lines. We considered the index residence at the time of the case's diagnosis or the control's interview and all other California residences of each subject for 7 years before study entry. We obtained wire codes for eligible residences of 76% and for index residences of 99% of subjects. Using the Kaune-Savitz wire code classification, the relative risk for longest held residences coded as "high" compared with "low" was 0.9 [95% confidence interval (CI) = 0.7-1.3], while relative risk and 95% CIs for front door spot measures of 1.01-2 milligauss, 2.01-3 milligauss, and higher than 3 milligauss compared with < or =1 milligauss were 1.0 (0.7-1.4), 0.6 (0.3-1.1), and 1.7 (0.8-3.6). Adjustment for age, gender, race, and whether the subject owned the residence did not meaningfully alter these findings, nor did comparisons using index or highest coded residence. Because of potential exposure misclassification and the unknown pertinent exposure period, these data cannot provide strong support against, but clearly do not support an association between, adult glioma and residential power frequency electromagnetic field exposures.

Host-cell positive transcription elongation factor b kinase activity is essential and limiting for HIV type 1 replication

HIV-1 gene expression and viral replication require the viral transactivator protein Tat. The RNA polymerase II transcriptional elongation factor P-TEFb (cyclin-dependent kinase 9/cyclin T) is a cellular protein kinase that has recently been shown to be a key component of the Tat-transactivation process. For this report, we studied the requirement for P-TEFb in HIV-1 infection, and we now show that P-TEFb is both essential and limiting for HIV-1 replication. Attenuation of P-TEFb kinase activity either by expression of a dominant-negative cyclin-dependent kinase 9 transgene or through the use of small-molecule inhibitors suppresses HIV-1 gene expression and HIV-1 replication. Inhibition of HIV-1 replication is affected in a manner consistent with a direct and specific effect on P-TEFb and the known functional role of P-TEFb in Tat-activated transcription. Tat-activated expression of HIV-1 genes seems uniquely dependent on P-TEFb, as inhibition of P-TEFb activity and HIV-1 replication can be achieved without compromising cell viability or RNA polymerase II-dependent cellular gene transcription. Selective inhibition of the P-TEFb kinase may therefore provide a novel approach for developing chemotherapeutic agents against HIV-1.

Altered multidrug resistance phenotype caused by anthracycline analogues and cytosine arabinoside in myeloid leukemia

The expression of P-glycoprotein (Pgp) is often increased in acute myeloid leukemia (AML). However, little is known of the regulation of Pgp expression by cytotoxics in AML. We examined whether Pgp expression and function in leukemic blasts was altered after a short exposure to cytotoxics. Blasts were isolated from 19 patients with AML (15 patients) or chronic myeloid leukemia in blastic transformation (BT-CML, 4 patients). Pgp expression and function were analyzed by flow cytometric analysis of MRK 16 binding and Rhodamine 123 retention, respectively. At equitoxic concentrations, ex vivo exposure for 16 hours to the anthracyclines epirubicin (EPI), daunomycin (DAU), idarubicin (IDA), or MX2 or the nucleoside analogue cytosine arabinoside (AraC) differentially upregulated MDR1/Pgp expression in Pgp-negative and Pgp-positive blast cells. In Pgp-negative blasts, all four anthracyclines and AraC significantly increased Pgp expression (P =.01) and Pgp function (P =.03). In contrast, MX2, DAU, and AraC were the most potent in inducing Pgp expression and function in Pgp positive blasts (P <.05). A good correlation between increased Pgp expression and function was observed in Pgp-negative (r =.90, P =.0001) and Pgp-positive blasts (r =.77, P =.0002). This increase in Pgp expression and function was inhibited by the addition of 1 micromol/L PSC 833 to blast cells at the time of their exposure to these cytotoxics. In 1 patient with AML, an increase in Pgp levels was observed in vivo at 4 and 16 hours after the administration of standard chemotherapy with DAU/AraC. Upregulation of Pgp expression was also demonstrated ex vivo in blasts harvested from this patient before the commencement of treatment. In 3 other cases (1 patient with AML and 2 with BT-CML) in which blasts were Pgp negative at the time of initial clinical presentation, serial samples at 1 to 5 months after chemotherapy showed the presence of Pgp-positive blasts. All 3 patients had refractory disease. Interestingly, in all 3 cases, upregulation of Pgp by cytotoxics was demonstrated ex vivo in blasts harvested at the time of presentation. These data suggest that upregulation of the MDR1 gene may represent a normal response of leukemic cells to cytotoxic stress and may contribute to clinical drug resistance.

Terminal differentiation of normal human oral keratinocytes is associated with enhanced cellular TGF-beta and phospholipase C-gamma 1 levels and apoptotic cell death

Subculture of primary normal human oral keratinocytes (NHOK) results in terminal differentiation, leading to cell death. To investigate whether the subculture-induced death of NHOK is due to apoptosis, we studied transferase-mediated dUTP nick end labeling (TUNEL)-positive cells, DNA fragmentation, and expression of several apoptosis-associated genes from NHOK with different passage numbers. We also determined the effect of transforming growth factor beta1 (TGF-beta1) on the induction of apoptosis in NHOK. We were able to subculture primary NHOK up to the fifth passage, at which point cells showed morphological features of differentiation. Appearance of DNA fragmentation concurrently occurred with an increase in the number of TUNEL-positive cells with higher passage numbers. The level of cellular p53 proteins was gradually decreased by the continued passage of cells, whereas the levels of intracellular and secreted TGF-beta and phospholipase C-gamma1 (PLC-gamma1) were significantly elevated by serial subculture. Exogenous TGF-beta1 also induced differentiation and apoptosis of proliferating NHOK. These data indicate that terminal differentiation of NHOK is associated with apoptosis, which is, in part, linked to elevated cellular levels of TGF-beta and PLC-gamma1.

Effects of continuous localized infusion of granulocyte-macrophage colony-stimulating factor and inoculations of irradiated glioma cells on tumor regression

OBJECT

Glioblastoma multiforme (GBM) is a malignant tumor of the central nervous system that directly suppresses immunological defenses in vitro and in vivo. The authors used the peripheral delivery of continuously infused granulocyte-macrophage colony-stimulating factor (GM-CSF) in the presence of irradiated tumor antigens as a tumor-specific stimulant to dendritic cells to initiate an immune response to GBM in rats.

METHODS

The 9L gliosarcoma tumors were established in the flanks of syngeneic Fischer 344 rats. Osmotic minipumps implanted in the animals' contralateral flanks continuously delivered recombinant GM-CSF (0, 0.1, 1, or 10 ng/day) for 28 days. Irradiated gliosarcoma cells were intermittently injected at the site of the GM-CSF infusion. Animals in the saline control group (0 ng/day GM-CSF) died on Day 59 with average tumor volumes greater than 30,000 mm3. This control group was significantly different from the GM-CSF-treated animals, which all survived with average tumor volumes that peaked on Day 23 and later regressed completely. Tumor growth as well as peak tumor volumes (5833+/-2284 mm3, 3294+/-1632 mm3, and 1979+/-1142 mm3 for 0.1, 1, and 10 ng/day GM-CSF, respectively) in the different treatment groups reflected a significant dose-response relationship with the GM-CSF concentrations. All animals treated with GM-CSF and irradiated cells were resistant to additional challenges of peripheral and intracerebral gliosarcoma, even when they were inoculated 8 months after initial immunotherapy. The colocalization of GM-CSF and inactivated tumor antigens was required to stimulate immunoprotection. To test the efficacy of a peripherally administered immunological therapy on intracerebral brain tumors the authors transplanted 10(6) gliosarcoma cells into the striatum of treated and control animals. Subcutaneous pumps that released GM-CSF (10 ng/day) and irradiated gliosarcoma cells were placed in the treated animals. The control animals all died within 31 days after intracerebral tumor implantation. In contrast, 40% of the animals receiving GM-CSF-irradiated cell vaccinations survived beyond 300 days. These long-term survivors showed no evidence of gliosarcoma at the injection site on evaluation by magnetic resonance imaging.

CONCLUSIONS

These results suggest that the continuous localized delivery of subcutaneous GM-CSF in conjunction with inactivated tumor antigens can initiate a systemic response that leads to the regression of distant peripheral and intracerebral tumors. The success of this treatment illustrates the feasibility of tumor-specific peripheral immunological stimulation after tumor resection to prevent the recurrence of malignant brain tumors.

Deciphering the nuclear import pathway for the cytoskeletal red cell protein 4.1R

The erythroid membrane cytoskeletal protein 4.1 is the prototypical member of a genetically and topologically complex family that is generated by combinatorial alternative splicing pathways and is localized at diverse intracellular sites including the nucleus. To explore the molecular determinants for nuclear localization, we transfected COS-7 cells with epitope-tagged versions of natural red cell protein 4.1 (4.1R) isoforms as well as mutagenized and truncated derivatives. Two distant topological sorting signals were required for efficient nuclear import of the 4.1R80 isoform: a basic peptide, KKKRER, encoded by alternative exon 16 and acting as a weak core nuclear localization signal (4.1R NLS), and an acidic peptide, EED, encoded by alternative exon 5. 4.1R80 isoforms lacking either of these two exons showed decreased nuclear import. Fusion of various 4.1R80 constructs to the cytoplasmic reporter protein pyruvate kinase confirmed a requirement for both motifs for full NLS function. 4.1R80 was efficiently imported in the nuclei of digitonin-permeabilized COS-7 cells in the presence of recombinant Rch1 (human importin alpha2), importin beta, and GTPase Ran. Quantitative analysis of protein-protein interactions using a resonant mirror detection technique showed that 4.1R80 bound to Rch1 in vitro with high affinity (KD = 30 nM). The affinity decreased at least 7- and 20-fold, respectively, if the EED motif in exon 5 or if 4.1R NLS in exon 16 was lacking or mutated, confirming that both motifs were required for efficient importin-mediated nuclear import of 4.1R80.

Formulation of proteins in vacuum-dried glasses. II. Process and storage stability in sugar-free amino acid systems

The purpose of this research was to investigate the freeze- and vacuum-drying behavior of L-amino acids of current/potential use as adjuvants for formulating proteins. The analytical methods used were wide-angle x-ray diffraction, differential scanning calorimetry, and scanning electron microscopy. Protein analysis was performed either as an activity assay (lactate dehydrogenase [LDH]) or by size-exclusion chromatography (granulocyte colony-stimulating factor [rhG-CSF]). After samples were freeze-dried, only the four basic amino acids (arginine, lysine, histidine, and citrulline) formed amorphous solids, which, however, were partially crystalline. The remaining amino acids all formed fully crystalline solids. After samples were vacuum-dried, (20 degrees C, 0.1 mbar, 1 ml fill volume in 2-ml vials) fully crystalline solids were formed by all of the amino acids. For arginine, the addition of either HCl, H3PO4, or H2SO4 sufficient to form the respective salt produced amorphous solids after vacuum-drying, but they had high residual water contents and low glass transition temperatures (Tg). Addition of phenylalanine to arginine base inhibited crystallization of the latter at low concentrations during vacuum-drying procedure, leading to formation of a pure rubbery solid. At higher concentrations the phenylalanine crystallized, producing dry products with glass transition temperatures of > 60 degrees C. The process and storage stability of LDH and rhG-CSF in the vacuum-dried phenylalanine/arginine glasses was greatly improved at temperatures up to 40 degrees C compared with the unprotected proteins. Uptake of moisture during storage was, however, a complicating factor, reducing Tg, promoting crystallization, and leading to decreased protein stability. The PO4 salt of arginine produced especially high glass transition temperatures after it was vacuum-dried. These sugar-free amino acid formulations thus are potential stabilizes for proteins.

Expression of regeneration and tolerance factor on B cell chronic lymphocytic leukemias: a possible mechanism for escaping immune surveillance

Regeneration and tolerance factor (RTF) is a protein expressed on developing tissue such as the thymus and the placenta. RTF has been reported to down-regulate cell-mediated immune responses. To examine the potential role of tumor-derived RTF to suppressing antitumor responses, we analyzed a panel of seven B cell tumor lines for the membrane RTF using a fluorescein isothiocyanate (FITC) conjugated monoclonal antibody, which reacts with membrane RTF. All the B cell tumor lines we examined express RTF on the cell surface. We also tested conditioned media from these B cell lines for their ability to suppress IL-2R expression on activated cells. Conditioned media from each B cell line suppressed IL-2R expression on activated Jurkat T cells and activated peripheral blood mononuclear cells. A monoclonal antibody to the biologically active portion of RTF reversed this suppressive activity. Finally, the tumor cell population from patients with chronic lymphocytic leukemia was found to express cell surface RTF. Thus, RTF expression could be a new mechanism used by tumor cells to escape immune surveillance.

The tau mutation (val337met) disrupts cytoskeletal networks of microtubules

The missense point mutation found in the tau gene, which was segregated in a family with frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), has proved to be the causal molecule for widely spread dementia diseases. Here we examined the effects of the tau mutation using confocal analysis. When wild-type tau cDNA was introduced into cells, extensive cell processes and well-developed thick bundles of microtubules were induced. On the other hand, when altered tau cDNA with the mutation (valine337-methionine) was introduced, cell lost processes and microtubule networks resulted in more round cell shape but showed intact mitochondria or endoplasmic reticulum. We conclude that the tau mutation primarily affects the microtubules and resultantly causes the loss of cellular organization and function due to microtubule disruption.