Multiubiquitin chain binding and protein degradation are mediated by distinct domains within the 26 S proteasome subunit Mcb1

The 26 S proteasome is a multisubunit proteolytic complex responsible for degrading eukaryotic proteins targeted by ubiquitin modification. Substrate recognition by the complex is presumed to be mediated by one or more common receptor(s) with affinity for multiubiquitin chains, especially those internally linked through lysine 48. We have identified previously a candidate for one such receptor from diverse species, designated here as Mcb1 for Multiubiquitin chain-binding protein, based on its ability to bind Lys48-linked multiubiquitin chains and its location within the 26 S proteasome complex. Even though Mcb1 is likely not the only receptor in yeast, it is necessary for conferring resistance to amino acid analogs and for degrading a subset of ubiquitin pathway substrates such as ubiquitin-Pro-beta-galactosidase (Ub-Pro-beta-gal) (van Nocker, S., Sadis, S., Rubin, D.M., Glickman, M., Fu, H., Coux, O., Wefes, I., Finley, D., and Vierstra, R. D. (1996) Mol. Cell. Biol. 16, 6020-28). To further define the role of Mcb1 in substrate recognition by the 26 S proteasome, a structure/function analysis of various deletion and site-directed mutants of yeast and Arabidopsis Mcb1 was performed. From these studies, we identified a single stretch of conserved hydrophobic amino acids (LAM/LALRL/V (ScMcb1 228-234 and At-Mcb1 226-232)) within the C-terminal half of each polypeptide that is necessary for interaction with Lys48-linked multiubiquitin chains. Unexpectedly, this domain was not essential for either Ub-Pro-beta-gal degradation or conferring resistance to amino acid analogs. The domain responsible for these two activities was mapped to a conserved region near the N terminus. Yeast and Arabidopsis Mcb1 derivatives containing an intact multiubiquitin-binding site but missing the N-terminal region failed to promote Ub-Pro-beta-gal degradation and even accentuated the sensitivity of the yeast delta mcb1 strain to amino acid analogs. This hypersensitivity was not caused by a gross defect in 26 S proteasome assembly as mutants missing either the N-terminal domain or the multiubiquitin chain-binding site could still associate with 26 S proteasome and generate a complex indistinguishable in size from that present in wild-type yeast. Together, these data indicate that residues near the N terminus, and not the multiubiquitin chain-binding site, are most critical for Mcb1 function in vivo.

Epitope mapping of mouse monoclonal antibody EP-5C7 which neutralizes both human E- and P-selectin

The epitope of mouse monoclonal antibody (mAb) EP-5C7, which binds to and blocks both human E- and P-selectin, was mapped onto the protein structure of E-selectin. Analyses with E- and L-selectin chimeric proteins and randomly mutagenized E-selectins demonstrated that the EP-5C7 epitope consists of the amino acid residues at positions 21, 22, 23, 119 and 120 of E-selectin. The binding of three neutralizing anti-E-selectin mAb's (E-1E4, H18/7 and CL2), whose epitopes were found to overlap with the E-selectin binding site for carbohydrate ligands, was not affected by the amino acid substitutions at these five positions. Inspection of the three-dimensional structure of E-selectin indicated that the EP-5C7 epitope is located near the junction between the lectin and EGF-like domains. The ligand binding site was distant from the EP-5C7 epitope, suggesting that the amino acid residues in the EP-5C7 epitope play an important role other than ligand binding in selectin-mediated cell adhesion.

Fine mapping of the epitopes of humanized anti-L-selectin monoclonal antibodies HuDREG-55 and HuDREG-200

Blocking the function of L-selectin with a monoclonal antibody (mAb) is a promising way to prevent neutrophils from causing tissue damage during inflammation. HuDREG-55 and HuDREG-200 are humanized mAb which bind to human L-selectin and block its function as an adhesion molecule. To understand the mechanism of the action of HuDREG-55 and HuDREG-200, we determined their epitopes on L-selectin at the amino acid level. The analysis of human E- and L-selectin chimeric proteins demonstrated that the lectin domain of L-selectin is necessary for the binding of HuDREG-55 and HuDREG-200. Mutational analysis of Escherichia coli-expressed L-selectin showed that HuDREG-55 binding is sensitive to amino acid changes at positions 11, 56, 87, 89, 105, 107 and 111 (counting from the amino-terminus of mature L-selectin) while HuDREG-200 binding is sensitive to amino acid changes at 45, 46 and 47. Both epitopes are located close to the predicted carbohydrate binding site, indicating that HuDREG-55 and HuDREG-200 block the function of L-selectin by directly inhibiting the binding to carbohydrate ligands.

Akt phosphorylation of BAD couples survival signals to the cell-intrinsic death machinery

Growth factors can promote cell survival by activating the phosphatidylinositide-3'-OH kinase and its downstream target, the serine-threonine kinase Akt. However, the mechanism by which Akt functions to promote survival is not understood. We show that growth factor activation of the PI3'K/Akt signaling pathway culminates in the phosphorylation of the BCL-2 family member BAD, thereby suppressing apoptosis and promoting cell survival. Akt phosphorylates BAD in vitro and in vivo, and blocks the BAD-induced death of primary neurons in a site-specific manner. These findings define a mechanism by which growth factors directly inactivate a critical component of the cell-intrinsic death machinery.

[Comparision on the effects of ALI aeute liver injury of three species of concha haliotidis in mice]

The liver injury mice model with Haliotis ruber (Leach), Haliotis disus hannai Ino and Haliotis lacvigata (Donovan) was studied. The results indicated three species Haliotidis could versus carbon tetrachloride-induced ALI aeute liver injury in mice. Comparision of reduced serum glutamic-pyruvic transaminass (SGPT) activity showed Halitis disacus hannai Ino > Haliotis Lacvigata (Donovan) > Haliotis ruber (Leach). The Liver starch was determined. It is suggested protection liver effect of Haliotis discus hannai Ino and Haliotis lacvigata (Donovan) are most powerful.

14-3-3 zeta negatively regulates raf-1 activity by interactions with the Raf-1 cysteine-rich domain

Although Raf-1 is a critical effector of Ras signaling and transformation, the mechanism by which Ras promotes Raf-1 activation is complex and remains poorly understood. We recently reported that Ras interaction with the Raf-1 cysteine-rich domain (Raf-CRD, residues 139-184) may be required for Raf-1 activation. The Raf-CRD is located in the NH2-terminal negative regulatory domain of Raf-1 and is highly homologous to cysteine-rich domains found in protein kinase C family members. Recent studies indicate that the structural integrity of the Raf-CRD is also critical for Raf-1 interaction with 14-3-3 proteins. However, whether 14-3-3 proteins interact directly with the Raf-CRD and how this interaction may mediate Raf-1 function has not been determined. In the present study, we demonstrate that 14-3-3 zeta binds directly to the isolated Raf-CRD. Moreover, mutation of Raf-1 residues 143-145 impairs binding of 14-3-3, but not Ras, to the Raf-CRD. Introduction of mutations that impair 14-3-3 binding resulted in full-length Raf-1 mutants with enhanced transforming activity. Thus, 14-3-3 interaction with the Raf-CRD may serve in negative regulation of Raf-1 function by facilitating dissociation of 14-3-3 from the NH2 terminus of Raf-1 to promote subsequent events necessary for full activation of Raf-1.

Synthesis and in vitro activity of long-chain 5'-O-[(alkoxycarbonyl)phosphinyl]-3'-azido-3'-deoxythymidines against wild-type and AZT- and foscarnet-resistant strains of HIV-1

Lipophilic esters of 3'-azido-3'-deoxy-5'-O-(carboxyphosphinyl)thymidine (PFA-AZT) were synthesized and tested for antiretroviral activity in CD4+ HT4-6C cells infected with either wild-type HIV-1LAI, a PFA-resistant strain encoding a single-point mutation in reverse transcriptase (E89K), or an AZT-resistant clinical isolate (A018-post). Arbuzov condensation of 1-octadecyl, 1-eicosanyl, and 1-docosanyl chloroformate with trimethyl phosphite yielded the corresponding dimethyl long-chain alkyl triesters of PFA. Selective removal of one methyl group from the triesters with sodium iodide yielded monosodium salts, whereas treatment with bromotrimethylsilane cleaved both methyl groups while leaving the long-chain alkyl group intact. Neutralization of the resulting [(alkyloxy)carbonyl]phosphonic acids with 2 equiv of sodium methoxide afforded disodium salts of the phosphonic acid moiety. Similar chemistry was used to obtain the mono- and disodium salts of the cholesterol ester of PFA. Reaction of the triesters with phosphorous pentachloride, followed by coupling with AZT and O-demethylation with sodium iodide, afforded 3'-azido-3'-deoxy-5'-O-[[(1-octadecyloxy)carbonyl]phosphinyl ]thymidine (9a), 3'-azido-3'-deoxy-5'-O-[[(1-eicosanyloxy)carbonyl]phosphinyl ]thymidine (9b), 3'-azido-3'-deoxy-5'-O-[[(1-docosanyloxy)carbonyl]phosphinyl ]thymidine (9c), and 3'-azido-3'-deoxy-5'-O-[[(3 beta-cholest-5-enyloxy)carbonyl]phosphinyl]thymidine (9d). Concentrations of 9a-d found to inhibit replication of wild-type HIV-1LAI by 50% (EC50 values) as measured in a plaque reduction assay were in the 0.1-0.3 microM range as compared with 0.013 microM for AZT and 133 microM for PFA. The concentration at which toxicity was observed in 50% of the host cells (TC50 values) as measured by a visual grading scale of cellular morphology was 10 microM for 9a and 9d, 32 microM for 9b, and 320 microM for 9c. Thus, the TC50/EC50 ratio or selectivity index (SI) was 100 for 9a, 230 for 9b, and 1000 for 9c but only 33 for 9d, suggesting that the straight-chained fatty alcohol esters were more therapeutically selective. Similar TC50 and SI values were obtained for rapidly dividing CEM lymphoblasts as for HT4-6C cells. In assays against E89K, 9a-c had mean EC50 values of 0.13, 0.009, and 0.17 microM, whereas the EC50 of PFA was > 1000 microM and that of AZT was 0.009 microM; thus, E89K was highly resistant to PFA but not cross-resistant to either AZT or the lipophilic PFA-AZT conjugates. In viral replication assays against the A018C-post isolate, the mean EC50 values of 9a-c were 0.30, 0.53, and 0.77 microM as compared with 2.9 microM for AZT and 65 microM for PFA; thus, the virus recovered from a patient pretreated with AZT was not cross-resistant to either PFA or 9a-c. A notable feature of these results was that, in addition to being > 1000-fold more potent than PFA against the PFA-resistant mutant, the lipophilic PFA-AZT conjugates were more potent than PFA, as well as AZT, against AZT-resistant HIV-1.

Two new limonoids from the seeds of Microula sikkimensis

Two new limonoids, cis-p-hydroxycinnamoylrutaevin and trans-p-hydroxycinnamoylrutaevin were isolated along with three known limonoids. Their structures were deduced on the basis of their spectral data. This is the first report on the isolation of limonoids from seeds of Microula sikkimensis Hemsl.

Misclassification bias in estimates of bereavement effects

Prospective studies that examine marital status differences in health and mortality frequently fail to update information on marital status in statistical models. The authors illustrate how the resulting misclassification of marital status can produce substantial bias in estimates of bereavement effects associated with widowhood. They use as their main source of data the Longitudinal Study of Aging (LSOA), 1984-1990, a national survey of persons aged 70 years and older. The estimates are based primarily on 3,192 respondents who were married and cohabiting with their spouses at the time of the baseline survey and who could be matched to their spouses' records. Comparisons of widowhood status derived from matched spouse records with reported marital status recorded in LSOA interviews demonstrate that reliance on interview information leads to substantial misclassification of marital status. Results from survival models indicate that estimates of marital status effects are sensitive to whether and how marital status is updated after baseline interviews. For example, updating marital status in hazard models from interview information alone indicates a protective effect of widowhood, whereas classifying widowhood on the basis of spouses' death records reveals a significant bereavement effect (relative mortality risks between 1.3 and 1.4).

[Comparative studies on pharmacological and toxic actions of raw fructus Psoraleae and its salt-baked and improved salt-baked products]

The pharmacological and toxic actions of raw Fructus Psoraleae and its salt-baked, and improved salt-baked products were comparatively studied. The leucogenic action of the improved salt-baked product was more effective than that of the original salt-baked one. But no significant difference in antidiarrheal or antiandrogenoid effect was found between the two salt-baked products. The toxicity(LD50 and the injury on kidney) of the improved salt-baked product was lower than that of the salt-baked. one. The results indicate that this improved processing method would contribute to increasing the efficacy and decreasing the toxicity of Fructus Psoraleae.

Raf-1 kinase and exoenzyme S interact with 14-3-3zeta through a common site involving lysine 49

14-3-3 proteins are a family of conserved dimeric molecules that bind to a range of cellular proteins involved in signal transduction and oncogenesis. Our solution of the crystal structure of 14-3-3zeta revealed a conserved amphipathic groove that may allow the association of 14-3-3 with diverse ligands (Liu, D., Bienkowska, J., Petosa, C., Collier, R. J., Fu, H., and Liddington, R. (1995) Nature 376, 191-194). Here, the contributions of three positively charged residues (Lys-49, Arg-56, and Arg-60) that lie in this Raf-binding groove were investigated. Two of the charge-reversal mutations greatly (K49E) or partially (R56E) decreased the interaction of 14-3-3zeta with Raf-1 kinase, whereas R60E showed only subtle effects on the binding. Interestingly, these mutations exhibited similar effects on the functional interaction of 14-3-3zeta with another target protein, exoenzyme S (ExoS), an ADP-ribosyltransferase from Pseudomonas aeruginosa. The EC50 values of 14-3-3zeta required for ExoS activation increased by approximately 110-, 5-, and 2-fold for the K49E, R56E, and R60E mutants, respectively. The drastic reduction of 14-3-3zeta/ligand affinity by the K49E mutation is due to a local electrostatic effect, rather than the result of a gross structural alteration, as evidenced by partial proteolysis and circular dichroism analysis. This work identifies the first point mutation (K49E) that dramatically disrupts 14-3-3zeta/ligand interactions. The parallel effects of this single point mutation on both Raf-1 binding and ExoS activation strongly suggest that diverse associated proteins share a common structural binding determinant on 14-3-3zeta.

[Toxic studies on various processed products of Fructus Psoraleae]

Toxic studies on Fructus Psoraleae (FP) and its processed products are carried on. LD50 is 37.7 +/- 0.54 g crude drug/kg in oral administration of raw FP in comparison with 43.25 +/- 6.1/kg in that of Salt-bake one in mice. When 5.0 g/kg is given by oral for 14 days, the wet weight of testicles, preputial galnds, prostate and semianl vesicle is decreased in raw FP and its stir-bake tested groups. The wet weight of preputial glends, prostate, seminal vesicle in Lei Gong's Procession group, or prostate, and seminal vesicle in salt-steam group is also decreased to a certain extent. But no significant change on the weight of those sex organs is found in liquor-bake or salt-bake procession group, The glomerulal cell hyperplasia and cloudy swelling of renal tubules are induced by administration of raw FP in pathological examination.

ATPase and ubiquitin-binding proteins of the yeast proteasome

The 26S proteasome is a 2-Megadalton proteolytic complex with over 30 distinct subunits. The 19S particle, a subcomplex of the 26S proteasome, is thought to confer ATP-dependence and ubiquitin-dependence on the proteolytic core particle of the proteasome. Given the complexity of the 19S particle, genetic approaches are likely to play an important role in its analysis. We have initiated biochemical and genetic studies of the 19S particle in Saccharomyces cerevisiae. Here we describe the localization to the proteasome of several ATPases that were previously proposed to be involved in transcription. Independent studies indicate that the mammalian 26S proteasome contains closely related ATPases. We have also found that the multiubiquitin chain binding protein Mcb1, a homolog of the mammalian S5a protein, is a subunit of the yeast proteasome. However, contrary to expectation, MCB1 is not an essential gene in yeast. The mcb1 mutant grows at a nearly wild-type rate, and the breakdown of most ubiquitin-protein conjugates is unaffected in this strain. One substrate, Ub-Proline-beta gal, was found to require MCB1 for its breakdown, but it remains unclear whether Mcb1 serves as a ubiquitin receptor in this process. Our data suggest that the recognition of ubiquitin conjugates by the proteasome is a complex process which must involve proteins other than Mcb1.

[Ending diatomic molecular terms]

A method is discussed to find diatomic molecular terms of equivalent and non-equivalent configuration.

[Comparison of changes of bone mass, parathyroid hormone and calcitonin between two animal models of bone loss]

The changes in bone mass, blood parathyroid hormone (PTH) and calcitonin (CT) between rats suspended for 14 and 21 days, simulated weightlessness, and rats ovariectomized (OVX) for 30 and 60 days were observed. The results revealed that mineral density of T6 and L3 was significantly increased in rats suspended for 14 days. T6 mineral density was also significantly increased in rats suspended for 21 days, but L3 mineral density was significantly decreased. T6 mineral density had no change in OVX rats, but L3 mineral density was significantly decreased in them both for 30 and 60 days. Mineral content at proximal 1/3 of femur shaft was significantly decreased in rats suspended for 14 and 21 days, and in rats OVX for 60 days. Bone biomechanical properties of suspended rats were more seriously deteriorated than that in OVX rats. There was no change in blood PTH, but CT was significantly increased in rats suspended for 14 and 21 days. Blood PTH and CT were significantly decreased in rats OVX for 30 and 60 days. The results indicate that the mineral redistribution and bone loss are presented in trabecular bone of suspended rats, but not in OVX rats. The deterioration of bone quality was more seriously in suspended rats than that in OVX rats. Both the cortical and trabecular bone in the two models were affected.

Selection of diphtheria toxin active-site mutants in yeast. Rediscovery of glutamic acid-148 as a key residue

Saccharomyces cerevisiae was transformed with expression plasmids carrying the DTA gene under control of the GAL1 promoter; colonies that formed under inducing conditions were selected; and plasmids from these colonies were screened for mutations in DTA that failed to block expression of the protein. Substitutions at three sites were identified, all of which are in the active-site cleft; and each of the substitutions reduced ADP-ribosyltransferase activity by > 10(5). The substitutions include a charge reversal mutation of a catalytically important residue (Glu148Lys) and replacements of either of two glycines (Gly22 and Gly52) with bulky residues. The fact that multiple mutations were identified in these same residues implies that there are relatively few sites at which substitutions ablate ADP-ribosyltransferase activity without blocking expression of the full-length protein. Incorporation of a primary attenuating mutation into the DTA gene allowed S. cerevisiae also to be used to select complementary secondary mutations which altered activity less drastically. Besides elucidating structure-activity relationships, mutations identified by these approaches may be useful in designing new vaccines.

[Study on tumor necrosis factor receptor of human gastric cancer cells]

OBJECTIVE

To explore the relationship between the number of tumor necrosis factor receptors (TNFR) and the degree of differentiation of gastric cancer cells, and the relationship between the number of TNFR and the cytotoxicity of tumor necrosis factor mutant (TNF-m).

METHODS

With 125I-TNF-m, the radio-ligand binding assay was used to detect the TNFR on three gastric cancer cell lines (MKN28, SGC7901 MKN45) with from high to low degrees of differentiation. MTT colorimetric method was used to study the cytotoxicity of TNF-m on the three gastric cancer cell lines in vitro.

RESULTS

The number of TNFR of the three gestric cancer cells was 9.8 x 10(-12) nmol, 5.6 x 10(-12) nmol and 3.2 x 10(-12) nmol per cell respectively it differed significent from each other (P < 0.05) but the dissociation constant was basically the same. The rate of TNF-m internalization of the three gastric cancer cells was nearly the same and temperature dependent. The half-life of TNFR was about 90 mins. The ratio of membrane receptors to cytoplasm receptors was about 0.5. The maximum killing rate of TNF-m was 86%, 60% and 34% for MKN28, SGC7901, MKN45 cells, respectively, which were significantly different (P < 0.05). Killing rate of TNF-m to these cells at 39 degrees C was higher than at 37 degrees C.

CONCLUSIONS

The number of TNFR on the surface of gastric cancer cells was associated with the degree of differentiation of gastric cancer cells. The cytotoxicity of TNF-m was related to the number of TNFR and the rate of internalization of TNF-m.

Magnetic stimulation of muscle evokes cerebral potentials by direct activation of nerve afferents: a study during muscle paralysis

We tested the hypothesis that magnetic stimulation of muscle evokes cerebral potentials by causing a muscle contraction that then activates muscle receptors. We measured cerebral evoked potentials accompanying magnetic stimulation of muscle in 3 patients during surgery both before and after muscle paralysis with succinylcholine, a depolarizing agent. The magnetic stimulation was at low intensity (30%) and at a 2/s rate. The administration of succinylcholine sufficient to produce muscle paralysis did not alter cerebral potentials evoked by either low-intensity magnetic stimulation of muscle (gastrocnemius/soleus) or electrical stimulation of peripheral nerve (tibial nerve). In 1 normal subject, the S1 nerve root action potentials conducting at rapid velocity (> 60 m/s) were detected at the S1 foramen with a needle electrode using electrical stimulation of the tibial nerve. However, no S1 nerve root potentials could be identified to magnetic stimulation of muscle that evoked a cerebral potential. We conclude that magnetic stimulation of muscle activates terminal afferents in the muscle to provide the afferent drive for the cerebral potentials independent of muscle contraction. The failure to detect the afferent volley in S1 nerve root to magnetic stimulation suggests that only a few afferents are activated or that the activation of afferents is temporally dispersed.

PCR cloning of the cDNA encoding baboon L-selectin

The cDNA encoding baboon L-selectin was isolated from baboon peripheral blood lymphocytes-derived cDNA and its nucleotide (nt) sequence was determined. The deduced 372-amino acid (aa) sequence of baboon L-selectin is 95% identical to that of human L-selectin.

The multiubiquitin-chain-binding protein Mcb1 is a component of the 26S proteasome in Saccharomyces cerevisiae and plays a nonessential, substrate-specific role in protein turnover

The 26S proteasome is an essential proteolytic complex that is responsible for degrading proteins conjugated with ubiquitin. It has been proposed that the recognition of substrates by the 26S proteasome is mediated by a multiubiquitin-chain-binding protein that has previously been characterized in both plants and animals. In this study, we identified a Saccharomyces cerevisiae homolog of this protein, designated Mcb1. Mcb1 copurified with the 26S proteasome in both conventional and nickel chelate chromatography. In addition, a significant fraction of Mcb1 in cell extracts was present in a low-molecular-mass form free of the 26S complex. Recombinant Mcb1 protein bound multiubiquitin chains in vitro and, like its plant and animal counterparts, exhibited a binding preference for longer chains. Surprisingly, (delta)mcb1 deletion mutants were viable, grew at near-wild-type rates, degraded the bulk of short-lived proteins normally, and were not sensitive to UV radiation or heat stress. These data indicate that Mcb1 is not an essential component of the ubiquitin-proteasome pathway in S.cerevisiae. However, the (delta)mcb1 mutant exhibited a modest sensitivity to amino acid analogs and had increased steady-state levels of ubiquitin-protein conjugates. Whereas the N-end rule substrate, Arg-beta-galactosidase, was degraded at the wild-type rate in the (delta)mcb1 strain, the ubiquitin fusion degradation pathway substrate, ubiquitin-Pro-beta-galactosidase, was markedly stabilized. Collectively, these data suggest that Mcb1 is not the sole factor involved in ubiquitin recognition by the 26S proteasome and that Mcb1 may interact with only a subset of ubiquitinated substrates.

The incidence of insulin-dependent diabetes mellitus in urban districts of Shanghai (1989-1993)

A retrospective study on the incidence of insulin-dependent diabetes mellitus (IDDM) among children aged 0-14 years was carried out from 1989-1993 in urban Shanghai, China. The average annual population at risk (0-14 yr) consisted of 1,401,664 children. All the cases were collected from the hospitals (primary source) and from primary and middle schools and kindergartens (second source) with independent validation of case ascertainment. There were 53 IDDM cases from the primary source, 23 from the secondary source, with a total of 58. The ascertainment corrected total number of IDDM cases was 67 by the capture-recapture method. The average crude annual incidence rate was 0.83 [95% confidence interval (CI) 0.61-1.04] and ascertainment corrected incidence rate 0.96 (95% CI 0.80-1.12) per 100,000. Peak incidence fell in 1992 and in the 9 year-old group. The incidence of childhood IDDM in the urban districts of Shanghai was reconfirmed to be the lowest in the world but by comparing the results of former investigations a trend was found of increasing incidence of IDDM.

Phage display vectors for in vivo recombination of immunoglobulin heavy and light chain genes to make large combinatorial libraries

New phage display vectors for in vivo recombination of immunoglobulin (Ig) heavy (VH) and light (VL) chain variable genes, to make single-chain Fv fragments (scFv), were constructed. The VH and VL genes of monoclonal antibody (mAb) EP-5C7, which binds to both human E- and P-selectin, were cloned into a pUC19-derived plasmid vector, pCW93, and a pACYC184-derived phagemid vector, pCW99, respectively. Upon induction of Cre recombinase (phage P1 recombinase), the VH and VL genes were efficiently recombined into the same plasmid via the two loxP sites (phage P1 recombination sites), one located downstream from a VH gene in pCW93 and another upstream from a VL gene in pCW99. In the resulting phagemid, the loxP sequence also encodes a polypeptide linker connecting the VH and VL domains to form a scFv of EP-5C7. Whether expressed on the phage surface or as a soluble form, the EP-5C7 scFv showed specific binding to human E- and P-selectin. This phagemid vector system provides a way to recombine VH and VL gene libraries efficiently in vivo to make extremely large Ig combinatorial libraries.

Cancer mortality among shoe manufacturing workers: an analysis of two cohorts

OBJECTIVES

To examine the cancer risk of shoe manufacturing workers and evaluate whether the risk was associated with exposure to leather dust and solvents.

METHODS

Data from two historical cohort studies of shoe workers were expanded and analysed in parallel. A total of 4215 shoemakers from England contributing 103 726 person-years at risk and 2008 shoemakers from Florence, Italy, contributing 54,395 person-years at risk were included in the analysis. Exposure to leather dusts and solvents from glues was evaluated on the basis of job title information. Standardised mortality ratios (SMR) were calculated as ratios of observed deaths (Obs) over expected derived from national mortalities.

RESULTS

Overall mortality was lower than expected in both cohorts (English cohort: Obs 3314, SMR 81, 95% confidence interval (95% CI) 78-84; Florence cohort: Obs 333, SMR 87, 95% CI 78-97). An increased risk of nasal cancer was found (English cohort: Obs 12, SMR 741; Florence cohort: Obs 1, SMR 909). 10 of the 13 cases occurred among English workers employed in the manufacture of welted boots (SMR 926, 95% CI 444-1703), a sector of the industry thought to have had the highest exposure to leather dust. Mortality from leukaemia was not increased in the English cohort (Obs 16, SMR 89), but was increased in the Florence cohort (Obs 8, SMR 214, 95% CI 92-421); and the highest risk was found among shoe workers in Florence who were first exposed between 1950 and 1959 when exposure to benzene was substantial (Obs 3, SMR 536, 95% CI 111-1566). Some evidence for an excess risk of stomach, bladder, and kidney cancer, as well as multiple myeloma and non-Hodgkin's lymphoma was also found in the Florence cohort only among workers employed in jobs with the highest exposure to solvents.

CONCLUSIONS

These findings confirm the associations between exposure to leather dust and nasal cancer and between exposure to benzene and leukaemia in the shoe manufacturing industry and suggest that the risk of other cancers may be increased among workers exposed to solvents or glues.

Engineered biosynthesis of novel polyketides: regiospecific methylation of an unnatural substrate by the tcmO O-methyltransferase

TcmO is an O-methyltransferase that methylates the C-8 hydroxyl to Tcm B3, a four-ring aromatic intermediate in the tetracenomycin biosynthetic pathway of Streptomyces glaucescens. The gene encoding this enzyme was expressed in Streptomyces coelicolor CH999 together with the actinorhodin polyketide synthase (PKS) gene cluster, which is responsible for the biosynthesis of 3,8-dihydroxy-methylanthraquinone carboxylic acid (DMAC) and its decarboxylated analog, aloesaponarin. The resulting recombinant strain produced approximately equal quantities of aloesaponarin and a new product but no DMAC. Spectroscopic analysis revealed that the novel polyketide was the 3-O-methylated analog of DMAC. An in vitro radioisotopic assay was developed for tcmO. The enzyme requires S-adenosylmethionine as a co-substrate. It has a Km of 3 microM and a kcat of 2.7 min-1 for DMAC. A series of monocyclic, bicyclic, and tricyclic aromatic compounds were also tested as candidate substrates in vitro. Remarkably, none was modified by tcmO within detectable limits of the assay. Together, these results highlight the interesting molecular recognition features of this enzyme. On one hand, there appears to be some flexibility in the number and structures of unreactive rings, since both Tcm and B3 and DMAC are good substrates. However, 6-methylsalicylic acid, a monocyclic analog of the reactive ring, is not recognized by the enzyme. Likewise, neither aloesaponarin (which only differs from DMAC in the reactive ring) nor carminic acid (which only differs in the distal nonreactive ring) is modified. Thus, the binding energy for the tcmO-catalyzed methyl transfer appears to involve significant contributions from both the aromaticity and the functionality of polycyclic substrates.

Enhanced infectivity of modified bluetongue virus particles for two insect cell lines and for two Culicoides vector species

Previous studies (Mertens et al., Virology 157, 375-386, 1987) have shown that removal of the outer capsid layer from bluetongue virus (BTV) significantly reduces (approximately x 10(-4)) the infectivity of the resultant core particle for mammalian cells (BHK 21 cells). In contrast, the studies reported here, using a cell line (KC cells) derived from a species of Culicoides that can act as a vector for BTV (Culicoides variipennis), demonstrated a much higher infectivity of core particles than that in mammalian cells (approximately x 10(3)). This increase resulted in a specific infectivity for cores that was only 20-fold less than that of purified disaggregated virus particles (stored in the presence of 0.1% sodium-N-lauroylsarcosine (NLS)). Removal of this detergent caused intact virus particle aggregation and (as previously reported) resulted in an approximately 1 log10 drop in the specific infectivity of those virus particles which remained in suspension. In consequence the specific infectivity of core particles for the KC cells was directly comparable to that of the intact but aggregated virus. These data are compared with the results from oral infectivity studies using two vector species (C. variipennis and Culicoides nubeculosus), which showed similar infection rates at comparable concentrations of purified cores, or of the intact but aggregated virus particles (NLS was toxic to adult flies). The role of the outer core proteins (VP7) in cell attachment and penetration, as an alternative route of initiation of infection, is discussed. Previous studies (Mertens et al., Virology 157, 375-386, 1987) also showed that the outer capsid layer of BTV can be modified by proteases (including trypsin or chymotrypsin), thereby generating infectious subviral particles (ISVP). The specific infectivity of ISVP for mammalian cells (BHK21 cells) was shown to be similar to that of disaggregated virus particles. In contrast, we report a significantly higher specific infectivity of ISVP but not of the intact virus (approximately x 100) for two insect cell lines (KC cells and C6/36 mosquito cells (derived from Aedes albopictus)). In oral infection studies with adults of the two vector species, ISVP produced the same infection rate at approximately 100-fold lower concentrations than either core particles or the intact but aggregated virus particles. The importance of mammalian host serum proteases, or insect gut proteases, in modification of the intact virus particle to form ISVP and their role in initiation of infection and the vector status of the insect is discussed.

Engineered biosynthesis of novel polyketides: properties of the whiE aromatase/cyclase

The ORFVI from the cluster of genes, which is responsible for the biosynthesis of the Streptomyces coelicolor spore pigment, the whiE cluster, has been described as a bifunctional aromatase/cyclase. In order to evaluate its potential use for generating novel polyketides, combinations of this gene with those encoding minimal polyketide synthase enzymes with or without a ketoreductase from S. coelicolor A3(2) were constructed and analyzed in vivo. Analysis of the polyketide products generated from these constructs indicates that the whiE-ORFVI enzyme has properties similar to those of TcmN, although the whiE aromatase/cyclase normally acts on a polyketide intermediate that is four carbons longer than the TcmN substrate. The whiE aromatase/cyclase can influence the regiospecificity of the first cyclization of unreduced, but not reduced, backbones and is also responsible for the second ring aromatization. An unusual new polyketide, EM18, was identified which is not seen in equivalent strains expressing the tcmN aromatase/cyclase or the act aromatase genes. The structure of EM18 suggests that the WhiE-ORFVI product might have some unique properties within this family of polyketide synthase subunits, and may therefore be useful in the design of combinatorial biosynthetic strategies.

Deciphering the biosynthetic origin of the aglycone of the aureolic acid group of anti-tumor agents

BACKGROUND

Mithramycin, chromomycin, and olivomycin belong to the aureolic acid family of clinically important anti-tumor agents. These natural products share a common aromatic aglycone. Although isotope labeling studies have firmly established the polyketide origin of this aglycone, they do not distinguish between alternative biosynthetic models in which the aglycone is derived from one, two or three distinct polyketide moieties. We set out to determine the biosynthetic origin of this moiety using a recombinant approach in which the ketosynthase and chain-length factor proteins from the antibiotic-producer strain, which determine the chain length of a polyketide, are produced in a heterologous bacterial host.

RESULTS

The ketosynthase and chain-length factor genes from the polyketide synthase gene cluster from the mithramycin producer, Streptomyces argillaceus ATCC 12956, and the acyl carrier protein and ketoreductase genes from the actinorhodin polyketide synthase were expressed in Streptomyces coelicolor CH999. The recombinant strain produced a 20-carbon polyketide, comprising the complete backbone of the aglycone of mithramycin.

CONCLUSIONS

The aglycone moieties of mithramycin, chromomycin, and olivomycin are derived from a single polyketide backbone. The nascent polyketide backbone must undergo a series of regiospecific cyclizations to form a tetracenomycin-like tetracyclic intermediate. The final steps in the aglycone biosynthetic pathway presumably involve decarboxylation and oxidative cleavage between C-18 and C-19, followed by additional oxidation, reduction, and methylation reactions.

Antibiotic activity of polyketide products derived from combinatorial biosynthesis: implications for directed evolution

A library of over 100 polyketides, generated via combinatorial cloning of genes encoding subunits of aromatic polyketide synthases, was screened for molecules capable of inhibiting the growth of gram-positive bacteria. A total of 26 polyketides, with varying levels of antibiotic activity in filter-disk assays, were purified. Most bioactive polyketides were produced as relatively minor compounds (< 1 mg/l), although two major anthraquinones, with yields in the range of 10-100 mg/l, were also identified and structurally characterized. When tested against Bacillus subtilis 168 beta, they were found to cause a 50% reduction in colony-forming units at concentrations of 20 and 300 micrograms/ml, respectively. We speculate that many of the minor (and possibly more potent) bioactive polyketides are synthesized via nonspecific enzymatic modifications of shunt products derived from engineered polyketide synthase pathways. If so, then these 'fortuitous' pathways should be amenable to further rationally guided manipulation. Our results support the notion that combinatorial biosynthesis can be used to generate novel, biologically active molecules. They also point to the feasibility of designing mutagenesis selection experiments aimed at the directed evolution of organic molecules with desirable pharmaceutical properties.

[Survival rates in patients with systemic lupus erythematosus]

To assess the impact of demographic and clinical factors on prognosis in patients with systemic lupus erythematosus (SLE), we examined the survival rate by lifetable analysis in 566 patients. All patients were Shanghai citizens who were diagnosed as having SLE in Huashan Hospital between 1959 and 1992. According to American Rheumatism Association's preliminary criteria. The survival rate from the time of SLE onset was 93% at 1 year, 73% at 5 years and 60% at 10 years. On univariate analysis, we found that the following factors worsened the probability of survival; male, neuropsychiatric manifestation, pleurisy-pericarditis, anemia, thrombocytopenia, lymphocytopenia, proteinuria, hematuria, urinary cast, azotemia, decreased endogenous creatinine clearance, increased cholesterol in serum, hypocomplementemia, abnormal electrocardiograph and high corticosteroid dose of treatment. On multivariate analysis, we found the four independent risk factors were male, azotemia, hypocomplementemia and high corticosteroid dose of treatment.

Sink- and vascular-associated sucrose synthase functions are encoded by different gene classes in potato

Two differentially regulated classes of sucrose synthase genes, Sus3 and Sus4, were identified in potato. They cannot be classified as Sus1 and Sus2 types based on sequence homology and appear to have evolved after the divergence of the major families of dicotyledonous plants but before the divergence of tomato and potato. The potato sucrose synthase clones Sus3-65 and Sus4-16 share an 87% nucleotide identity in the coding regions, and both are interrupted by 13 introns, including a long leader intron. Potato Sus3 genes are expressed at the highest levels in stems and roots and appear to provide the vascular function of sucrose synthase. In contrast, Sus4 genes are expressed primarily in the storage and vascular tissue of tubers and appear to facilitate sink function. The genes are differentially regulated in root tips, with Sus3 expressed at high levels in the cell division zone and Sus4 expressed at high levels in the meristem and cap.

High-level tuber expression and sucrose inducibility of a potato Sus4 sucrose synthase gene require 5' and 3' flanking sequences and the leader intron

The 3.6 kb of 5' flanking sequence, leader intron, and 0.7 kb of 3' sequence from the potato sucrose synthase gene Sus4-16 are sufficient to direct high-level expression in developing tubers, in basal tissues of axillary buds and shoots, and in meristems and caps of roots, and to confer sucrose inducibility in leaves. By examining a series of deletion and substitution constructs in transgenic potato plants, we found that this pattern of expression requires 5' flanking sequences both upstream and downstream of position -1500 and that sequences between positions -1500 and -267 are essential for sucrose induction. Replacement of the native 3' sequence with the nopaline synthase 3' sequence resulted in the loss of sucrose inducibility and of expression in basal tissues of axillary buds. A general decrease in expression in other tissues was also observed. Removal of the 1612-bp leader intron also had a dramatic effect on both the pattern and level of expression.

High-level tuber expression and sucrose inducibility of a potato Sus4 sucrose synthase gene require 5' and 3' flanking sequences and the leader intron

The 3.6 kb of 5' flanking sequence, leader intron, and 0.7 kb of 3' sequence from the potato sucrose synthase gene Sus4-16 are sufficient to direct high-level expression in developing tubers, in basal tissues of axillary buds and shoots, and in meristems and caps of roots, and to confer sucrose inducibility in leaves. By examining a series of deletion and substitution constructs in transgenic potato plants, we found that this pattern of expression requires 5' flanking sequences both upstream and downstream of position -1500 and that sequences between positions -1500 and -267 are essential for sucrose induction. Replacement of the native 3' sequence with the nopaline synthase 3' sequence resulted in the loss of sucrose inducibility and of expression in basal tissues of axillary buds. A general decrease in expression in other tissues was also observed. Removal of the 1612-bp leader intron also had a dramatic effect on both the pattern and level of expression.

Sink- and vascular-associated sucrose synthase functions are encoded by different gene classes in potato

Two differentially regulated classes of sucrose synthase genes, Sus3 and Sus4, were identified in potato. They cannot be classified as Sus1 and Sus2 types based on sequence homology and appear to have evolved after the divergence of the major families of dicotyledonous plants but before the divergence of tomato and potato. The potato sucrose synthase clones Sus3-65 and Sus4-16 share an 87% nucleotide identity in the coding regions, and both are interrupted by 13 introns, including a long leader intron. Potato Sus3 genes are expressed at the highest levels in stems and roots and appear to provide the vascular function of sucrose synthase. In contrast, Sus4 genes are expressed primarily in the storage and vascular tissue of tubers and appear to facilitate sink function. The genes are differentially regulated in root tips, with Sus3 expressed at high levels in the cell division zone and Sus4 expressed at high levels in the meristem and cap.

A potato Sus3 sucrose synthase gene contains a context-dependent 3' element and a leader intron with both positive and negative tissue-specific effects

To examine which sequences are involved in regulating the potato sucrose synthase gene Sus3-65, we examined a series of deletion and substitution constructs in transgenic potato and tobacco plants. In a construct containing 3.9 kb of 5' flanking region, substitution of the native 3' sequence with the nopaline synthase 3' sequence and deletion of the leader intron did not significantly affect expression in vegetative tissues. However, in a construct containing only 320 bp of 5' flanking region, these changes had marked effects. Replacing the native 3' sequences with nopaline synthase 3' sequences caused a six- to 20-fold increase in expression in vascular tissue, and removing the leader intron almost completely abolished expression in potato plants. Surprisingly, removal of the leader intron from either the full-length construct or a construct containing only 320 bp of 5' flanking sequence reduced expression in vascular tissue of tobacco anthers at later stages of development but increased expression in pollen by more than 100-fold.

Crystal structure of the zeta isoform of the 14-3-3 protein

The 14-3-3 family of proteins have recently been identified as regulatory elements in intracellular signalling pathways: 14-3-3 proteins bind to oncogene and proto-oncogene products, including c-Raf-1 (refs 2-5), c-Bcr (ref. 6) and polyomavirus middle-T antigen; overexpression of 14-3-3 activates Raf kinase in yeast and induces meiotic maturation in Xenopus oocytes. Here we report the crystal structure of the major isoform of mammalian 14-3-3 proteins at 2.9 A resolution. Each subunit of the dimeric protein consists of a bundle of nine antiparallel helices that form a palisade around an amphipathic groove. The groove is large enough to accommodate a tenth helix, and we propose that binding to an amphipathic helix represents a general mechanism for the interaction of 14-3-3 with diverse cellular proteins. The residues in the dimer interface and the putative ligand-binding surface are invariant among vertebrates, yeast and plants, suggesting a conservation of structure and function throughout the 14-3-3 family.

Binding characteristics of glucocorticoid receptor in synaptic plasma membrane from rat brain

The study was carried out to identify the specific glucocorticoid membrane binding site (GCMB) on synaptic plasma membrane (SPM), and to investigate the ligand binding properties and physico-chemical characteristics of GCMB. The radioligand binding assay showed that tritiated corticosterone ([3H]B) could bind to GCMB specifically with positive cooperativity. For SPM, the binding capacity (R(zero)) was 46.67 +/- 4.62 fmol/mg protein; the dissociation constant (Kd), 97.48 +/- 18.85 nmol/L, and the Hill coefficient, 1.633 +/- 0.082. Various steroids bound with GCMB in the following rank order: RU26752, aldosterone > corticosterone, cortisol > RU26988, progesterone, R5020, triamcinolone acetonide > testosterone, estradiol > RU38486 > dexamethasone. GCMB, which could be solubilized by detergent Triton X-100, showed thermal stability, although it was susceptible to hydrolysis by trypsin and to the reducing agent, mercaptoethanol. The addition of divalent cations (Ca2+, Mg2+) was beneficial to the ligand binding. The results strongly indicate that GCMB, fulfilling the basic criteria for a receptor, constitutes a novel type of glucocorticoid receptor on neuronal membrane which is significantly different from the cytosolic glucocorticoid receptors.

Cancer and occupational exposure to inorganic lead compounds: a meta-analysis of published data

OBJECTIVES

To review and summarise the epidemiological evidence on the carcinogenicity of occupational exposure to inorganic lead.

METHODS

Case-control and cohort studies were reviewed and combined for meta-analysis. Fixed and random effect methods were used to estimate the summary effects.

RESULTS

The combined results show a significant excess risk of overall cancer, stomach cancer, lung cancer, and bladder cancer, with relative risk ratios (RRs) and 95% confidence intervals (95% CIs) in the meta-analysis of 1.11 (1.05-1.17), 1.33 (1.18-1.49), 1.29 (1.10-1.50), and 1.41 (1.16-1.71) respectively. The RR (95% CI) for kidney cancer was also high, but did not reach significance (1.19 (0.96-1.48)). A separate analysis of studies of heavily exposed workers provided slightly increased RRs for cancers of the stomach (1.50) and lung (1.42).

CONCLUSIONS

The findings from the workers with heavy exposure to lead provided some evidence to support the hypothesis of an association between stomach and lung cancer and exposure to lead. The main limitation of the present analysis is that the excess risks do not take account of potential confounders, because little information was available for other occupational exposures, smoking, and dietary habits. To some extent, the risk of lung cancer might be explained by confounders such as tobacco smoking and exposure to other occupational carcinogens. The excess risk of stomach cancer may also be explained, at least in part, by non-occupational factors. For bladder and kidney cancers, the excess risks are only suggestive of a true effect because of possible publication bias.

Retroreflecting ellipsometer for measuring the birefringence of optical disk substrates

A retroreflecting ellipsometer has been constructed for measuring the birefringence of optical disk substrates. In contrast to conventional ellipsometers with two mechanical arms, this system has only one arm along which both the incident and reflected beams travel. This construction eliminates the mechanical limitations of conventional ellipsometers, thereby permitting normal incidence on the sample. In addition, the single arm is adjustable in two dimensions, with the polar incident angle, θ(inc), varying from 0° to 70°, and the azimuthal incident angle, Φ(inc), varying from 0° to 360°. The condition of normal incidence permits accurate measurement of in-plane birefringence. The adjustability of both θ(inc) and Φ(inc) is necessary for the measurement of possible tilts of the index ellipsoid, and also for the variation of birefringence through the substrate thickness. Measurement results showing the useful features of the equipment are presented. The optics of the hemispherical assembly used for retroreflection as well as for the elimination of undesirable refractions are also studied by use of the ZEMAX lens design program.

Engineered biosynthesis of novel polyketides: evidence for temporal, but not regiospecific, control of cyclization of an aromatic polyketide precursor

BACKGROUND

Aromatic polyketide synthases (PKSs) catalyze the formation and cyclization of polyketide chains of variable lengths, generating a family of compounds of proven medical significance. Initial control over the regiospecificity of cyclization is believed to be exercised by the minimal PKS, composed of the three essential components for polyketide biosynthesis, which catalyzes an intramolecular aldol condensation towards the middle of the chain. Subsequent cyclization reactions are either catalyzed by additional components of the PKS, or occur in the absence of specific catalysts.

RESULTS

Structural and biosynthetic studies on SEK4b, a novel octaketide product of a minimal PKS, revealed an unusual cyclization pattern. The first cyclization (an aldol condensation) occurs at the methyl end of the unreduced polyketide backbone precursor. This is followed by hemiketal formation and lactonization. The overall structure of SEK4b is similar to that of SEK4, a previously-identified product of the same genetically-engineered strain, differing only in the positions of a methyl and a pyrone group around a common fused-ring system. The biosynthetic pathways of the two molecules are quite different, however. The yield of SEK4b relative to SEK4 is much higher in the absence of PKS components (aromatases and cyclases) acting later in the pathway.

CONCLUSIONS

In this cyclization pathway, the regiospecificity of cyclization is not directly controlled by the minimal PKS. Instead, we propose that the enzyme influences cyclization by controlling the timing of chain release. Chain release and cyclization may be concurrent with synthesis. Other PKS subunits appear to stabilize the complex of the PKS with the nascent chain, preventing premature release.

Engineered biosynthesis of novel polyketides: influence of a downstream enzyme on the catalytic specificity of a minimal aromatic polyketide synthase

To identify the minimum set of polyketide synthase (PKS) components required for in vivo biosynthesis of aromatic polyketides, combinations of genes encoding subunits of three different aromatic PKSs--act from Streptomyces coelicolor A3(2) (an actinorhodin producer), fren from Streptomyces roseofulvus (a frenolicin and nanaomycin producer), and tcm from Streptomyces glaucescens (a tetracenomycin producer)--were expressed in a recently developed Streptomyces host-vector system. The "minimal" components (ketosynthase/putative acyltransferase, chain length-determining factor, and acyl carrier protein) were produced with and without a functional polyketide ketoreductase and/or cyclase, and the polyketide products of these recombinant strains were structurally characterized. Several previously identified polyketides were isolated in addition to two previously unidentified polyketides, dehydromutactin and SEK 15b, described here. The results proved that the act cyclase is not required for the biosynthesis of several aberrantly cyclized products that have been previously reported. They are also consistent with earlier conclusions that the minimal PKS controls chain length as well as the regiospecificity of the first cyclization and that it can do so in the absence of both a ketoreductase and a cyclase. However, the ability of the minimal tcm PKS to synthesize two different singly cyclized intermediates suggests that it is unable to accurately control the course of this reaction by itself. In the presence of a downstream enzyme, the flux through one branch of the cyclization pathway increases relative to the other. We propose that these alternative specificities may be due to the ability of downstream enzymes to associate with the minimal PKS and to selectively inhibit a particular branch of the cyclization pathway.

A NaCl-regulated plant gene encoding a brain protein homology that activates ADP ribosyltransferase and inhibits protein kinase C

A cDNA clone pCZ1, with a 1.1 kb insert, was isolated from a NaCl-adapted tobacco cell cDNA library that encodes an apparently full-length 29 kDa protein (251 amino acids) with a calculated pI of 5.7. The encoded peptide had a high amino acid sequence identity with bovine 14-3-3 protein which was originally found as an abundant protein in the animal central nervous system. Recently, proteins with sequence identity to 14-3-3 protein have also been found in plants, insects and yeast, and appear to have diverse physiological functions. Similar to the bovine brain 14-3-3 protein, the recombinant pCZ1 protein stimulated ADP-ribosylation of protein substrate by ADP-ribosyltransferase from the plant and animal pathogenic bacterium Pseudomonas aeruginosa. This recombinant protein also inhibited protein kinase C activity in vitro. Southern blot analyses indicated that most likely five genes encoding 14-3-3-like proteins are present in tobacco. The pCZ1 cDNA insert hybridized to a single mRNA of 1.1 kb from cultured tobacco cells. The level of this mRNA transcript in tobacco cells was downregulated upon adaptation to NaCl but was unaffected by short-term treatment with NaCl, ABA or ethylene. In tobacco plants, expression of transcript that hybridized to pCZ1 was tissue specific, and was most abundant in roots and flower parts. Monoclonal antibody raised against GF14 protein, a maize protein with substantial sequence identity with 14-3-3 protein detected two bands on SDS-PAGE of total proteins from unadapted tobacco cells and only a single band from cells adapted to NaCl. The GF14 antibody was also used to illustrate that the G-box element of a salt-induced gene is associated with a 14-3-3-type protein.

Measurement of the wavelength dependence of birefringence for optical disk substrates

The in-plane and vertical birefringence of polycarbonate plastic substrates of optical disks are measured for wavelengths between 360 and 860 nm, which covers the full range of interest for blue as well as for the current red and infrared recording. It is found that the birefringence generally decreases as the measurement wavelength is increased. In a typical case, the in-plane birefringence, Δn‖ goes from 1.7 × 10(-5) to 1.2 × 10(-5), and the vertical birefringence, Δn⊥, drops from 7.5 δ 10(4-) to 5.7 × 10(4-) in the wavelength range from 360 to 860 nm.

Association of the protein kinases c-Bcr and Bcr-Abl with proteins of the 14-3-3 family

In this study, a protein that interacts with sequences encoded by the first exon of the protein kinase Bcr was cloned. The Bcr-associated protein 1 (Bap-1) is a member of the 14-3-3 family of proteins. Bap-1 interacts with full-length c-Bcr and with the chimeric Bcr-Abl tyrosine kinase of Philadelphia chromosome (Ph1)-positive human leukemias. Bap-1 is a substrate for the Bcr serine-threonine kinase and is also phosphorylated on tyrosine by Bcr-Abl but not by c-Abl. Bap-1 may function in the regulation of c-Bcr and may contribute to the transforming activity of Bcr-Abl in vivo. 14-3-3 proteins are essential for cell proliferation and have a role in determining the timing of mitosis in yeast. Through direct binding to sequences present in Bcr and in other proteins implicated in signaling, the mammalian 14-3-3 proteins may link specific signaling protein components to mitogenic and cell-cycle control pathways.

Association of the protein kinases c-Bcr and Bcr-Abl with proteins of the 14-3-3 family

In this study, a protein that interacts with sequences encoded by the first exon of the protein kinase Bcr was cloned. The Bcr-associated protein 1 (Bap-1) is a member of the 14-3-3 family of proteins. Bap-1 interacts with full-length c-Bcr and with the chimeric Bcr-Abl tyrosine kinase of Philadelphia chromosome (Ph1)-positive human leukemias. Bap-1 is a substrate for the Bcr serine-threonine kinase and is also phosphorylated on tyrosine by Bcr-Abl but not by c-Abl. Bap-1 may function in the regulation of c-Bcr and may contribute to the transforming activity of Bcr-Abl in vivo. 14-3-3 proteins are essential for cell proliferation and have a role in determining the timing of mitosis in yeast. Through direct binding to sequences present in Bcr and in other proteins implicated in signaling, the mammalian 14-3-3 proteins may link specific signaling protein components to mitogenic and cell-cycle control pathways.

Interaction of the protein kinase Raf-1 with 14-3-3 proteins

Members of a family of highly conserved proteins, termed 14-3-3 proteins, were found by several experimental approaches to associate with Raf-1, a central component of a key signal transduction pathway. Optimal complex formation required the amino-terminal regulatory domain of Raf-1. The association of 14-3-3 proteins and Raf-1 was not substantially affected by the activation state of Raf.