[Activation of p38 and c-Jun NH2-terminal kinase mitogen-activated protein kinases in human prostate carcinoma cell lines with different metastatic potentials]

OBJECTIVE

To investigate the influence of P2 purinoceptor agonist ATP on p38 mitogen-activated protein kinases (MAPK) and JNK (c-Jun NH(2)-terminal kinase) signaling pathway in two human prostate cancer cell sublines (1E8 and 2B4) with different metastasis potentials.

METHODS

Activated p38 and JNK were detected by Western blot with phospho-specific antibodies directed against the dually phosphorylated active forms of p38 or JNK.

RESULTS

Exposure of 1E8 and 2B4 prostate cancer cells to ATP resulted in p38 activation in a concentration- and time-dependent manner. ATP-induced p38 activities were higher in metastatic 1E8 cells when compared with nonmetastatic 2B4 cells. JNK signaling pathway was not activated by ATP. An MEK inhibitor PD 98059 failed to inhibit ATP-induced p38 activation, while p38 inhibitor SB 203580 and P2 purinoceptor antagonist suramin effectively inhibited activation of p38, the inhibition rate being 1E8 83% and 79%, 2B4 81% and 69%. The response of ATP-stimulated p38 to G-protein modulator pertussis toxin in 1E8 and 2B4 cells was not obvious.

CONCLUSIONS

p38 but not JNK signaling pathway can be activated by P2 purinoceptor agonist ATP. Differences of p38 activation by ATP are noted between metastatic 1E8 cells and non-metastatic 2B4 cells. These results provide instructive clues to cancer malignant growth and metastasis research.

Osteopontin gene regulation by oscillatory fluid flow via intracellular calcium mobilization and activation of mitogen-activated protein kinase in MC3T3-E1 osteoblasts

Recently fluid flow has been shown to be a potent physical stimulus in the regulation of bone cell metabolism. However, most investigators have applied steady or pulsing flow profiles rather than oscillatory fluid flow, which occurs in vivo because of mechanical loading. Here oscillatory fluid flow was demonstrated to be a potentially important physical signal for loading-induced changes in bone cell metabolism. We selected three well known biological response variables including intracellular calcium (Ca(2+)i), mitogen-activated protein kinase (MAPK) activity, and osteopontin (OPN) mRNA levels to examine the response of MC3T3-E1 osteoblastic cells to oscillatory fluid flow with shear stresses ranging from 2 to -2 Newtons/m(2) at 1 Hz, which is in the range expected to occur during routine physical activities. Our results showed that within 1 min, oscillatory flow induced cell Ca(2+)i mobilization, whereas two MAPKs (ERK and p38) were activated over a 2-h time frame. However, there was no activation of JNK. Furthermore 2 h of oscillatory fluid flow increased steady-state OPN mRNA expression levels by approximately 4-fold, 24 h after exposure to fluid flow. The presence of both ERK and p38 inhibitors and thapsigargin completely abolished the effect of oscillatory flow on steady-state OPN mRNA levels. In addition, experiments using a variety of pharmacological agents suggest that oscillatory flow induces Ca(2+)i mobilization via the L-type voltage-operated calcium channel and the inositol 1,4,5-trisphosphate pathway.

[Inhibitory effect of antisense VEGF₁₂₁ and endostatin genes transfection on tumor growth and metastasis of human giant cell lung cancer]

BACKGROUND

To explore the co-operative inhibitory effect of antisense VEGF gene and endostatin gene transfection on tumor angiogenesis, tumor growth and metastasis of lung cancer.

METHODS

Antisense VEGF₁₂₁ cDNA was transfected into PG cells(PG-AS-VEGF) by lipofectin. After PG-AS-VEGF cells were xenografted to nude mice, PsectagA-endostatin gene was transfected into nude mice by electric pulse mediation. The MVDs in tumors and tumor biological characteristics were observed.

RESULTS

(1)The MVD in PG-AS-VEGF tumor in nude mice was significantly lower than that in PG-vector tumor (PG-AS-VEGF and PG-vector: 40.67±9.35 and 58.34±10.52, respectively) in nude mice. (2)There was no significant difference between the PG-vector tumor and PG-AS-VEGF tumor in early stage of the tumor growth in vivo. However, PG-AS-VEGF tumor grew significantly more slowly than PG-vector tumor after 18 days (P<0.05). (3)PG-AS-VEGF tumor could lead to regional and/or distant lymph node metastases (16.7%, 2/12), which was much more infrequent than that in PG-vector group (50%, 6/12). (4) PG-AS-VEGF tumor growth was remarkably inhibited by endostatin gene transfected at site of the tumor inoculation as compared with the control group in nude mice (P<0.05). (5)The PG-AS-VEGF tumors transfected with the endostatin gene at site of the tumor inoculation(AST) could also produce much lower regional and/or distant lymph node metastases rate (12.5%, 1/8) than that in the PG-AS-VEGF tumor transfected with the PsectagA vector (ASP)(75%, 6/8).

CONCLUSIONS

Endostatin gene transfection could cooperatively inhibit the growth and spontaneous lymph node metastasis of antisense VEGF gene transfected PG cells in nude mice.

[Study on the growth of H1299 cell line transfected transiently with mouse p53 minigenes with different codon 172 structures]

BACKGROUND

To investigate the effect on cell growth after transfected with mouse 172 wild-type p53 (Arg), pseudo-wild-type p53 (Arg->Leu) and mutant p53 (Arg->His).

METHODS

Vectors of three kinds of p53 minigene were transfected into p53-null H1299 cells through lipofectAMINE. Cells were collected at different time after transfection and analyzed by cell counting, flow cytometry and Western blotting.

RESULTS

Wild-type p53 and pseudo-wild-type p53 could induce cell apoptosis and cell cycle arrest at different time. Bax, p21(WAF1) and Mdm-2 were transactivated by wild-type p53 and pseudo-wild-type p53. No tumor growth suppression was observed in mutant p53 transfected cells.

CONCLUSIONS

Wild-type p53 and pseudo-wild-type p53 can inhibit cell growth by inducing apoptosis and cell cycle arrest through transactivation of Bax and p21(WAF1). There exists feedback loop between Mdm-2 and p53. The different biological effect between 172Leu and 172His shows that some p53 variants such as 172 Arg->Leu may act as wild-type p53.

[Supercritical fluid extraction of beta-elemene under lower pressure]

A method has been developed for the extraction and analysis of the active component beta-elemene from Rhizoma Atractylodis Macrocephalae by supercritical fluid extraction with CO2 containing ethanol. The article discusses some factors such as pressure, temperature and modifier that affect the selectivity. Class-selective extraction has been performed by varying the pressure. beta-Elemene could almost be extracted completely at lower pressure (12.0 MPa) and its relative amount was raised from 4.8% under higher pressure to 8.0% for lower pressure.

Determination of alcohols by high-performance liquid chromatography with fluorimetric detection after pre-column derivatisation with carbazole-9-N-acetic acid and chromatographic behaviour of alcoholic derivatives

Alcohols were derivatised to their carbazole-9-N-acetic acid (CRA) esters with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HCl) as the dehydrating agent. Studies on derivatisation conditions indicated that the coupling reaction proceeded rapidly and smoothly in the presence of a base catalyst in acetonitrile to give the corresponding sensitively fluorescent derivatives. The retention behaviour of alcohol derivatives was investigated by varying mobile phase compositions (ACN-water and MeOH-water). The parameters from the equation log k'=A-BX were evaluated by retention data of derivatives using an isocratic elution with different mobile phases. The results indicated that the parameters derived allowed computation of retention factors in good agreement with experiments. At the same time, a general equation was derived that makes possible predictions of partition coefficient in binary mobile phases with different proportions of organic solvent to water based on some simple regression analysis. The LC separation for the derivatised alcohols containing higher carbon alcohols showed good reproducibility on a reversed-phase C18 column with gradient elution. The detection limits (excitation at 335 nm, emission at 360 nm) for derivatised alcohols (signal-to-noise ratio=3:1) were in the range of 0.1-0.4 pg per injection.

Effect of slip on movement of body center of mass relative to base of support

OBJECTIVE

The purpose is to investigate the effect of balance conditions and slippery perturbation on the position and velocity of the body's center of mass relative to the body's base of support.

DESIGN

Twenty-two young and healthful subjects were investigated while their walk was perturbed by a soap patch applied over a force plate. A safety harness was used to prevent the subject from falling on knee or buttock.

BACKGROUND

Appropriate postural response to meet physiological biomechanical requirements is mandatory in restoration of balance upon slip.

METHODS

Twenty-two healthy subjects dressed with safety harness walked first without and then with slippery perturbation, guided by a metronome at 120 steps/min and 90 steps/min cadence. Data were collected from a motion analysis system and force plates.

RESULTS

For slippery perturbation, the displacement and velocity of center of mass with respect to base of support became smaller from heel strike to contralateral toe off. Subject's balance condition correlated significantly to the displacement of center of mass with respect to base of support (r=-0.51 at 120 steps/min and r=-0.471 at 90 steps/min), as well as the velocity (r=-0.834 at 120 steps/min, r=-0.673 at 90 steps/min) at contralateral toe off.

CONCLUSIONS

For slip during walking, smaller excursion and faster velocity of center of mass with respect to base of support were important for subjects regaining balance from heel strike to contralateral toe off. The critical time for subjects regaining stability is the first double support phase of the gait cycle.

RELEVANCE

It is confirmed that two variables, the displacement and the velocity of center of mass with respect to base of support, are valuable biomechanical factors and provide quantifiable determination for investigation of the balance condition in slipping.

Identification of metastasis associated gene G3BP by differential display in human cancer cell sublines with different metastatic potentials G3BP as highly expressed in non-metastatic

OBJECTIVE

To investigate genes involved in cancer metastasis, mRNA differential display was used to compare the levels of gene expression in two cell sublines derived from human giant cell carcinoma of lung (PG) which had different metastatic potentials.

METHODS

Using in vivo tumorigenicity and a spontaneous metastasis assay in nude mice, two sublines (BE1, LH7) from human giant cell carcinoma of lung (PG) with different metastatic potentials were isolated and characterized. mRNA differential display was used to compare the levels of gene expression between them and the obtained results were confirmed by Northern hybridization.

RESULTS

One differentially expressed band was nearly identical (99% homology) to Ras-GTPase-Activating protein SH3 domain binding protein (G3BP). G3BP displayed a strong expression in LH7 (non-metastatic in recipient nude mice) and a very weak expression in BE1 (100% metastatic frequency). The same different expression level of G3BP was detected in Northern hybridization with another panel of cell sublines with different metastatic potentials (established in our lab) derived from human prostate carcinoma cell line PC-3M.

CONCLUSION

Our results indicate that G3BP was implicated in cancer metastasis because of its differential expressions in the two panels of cell sublines with different metastatic potentials.

Neuropeptide Y-mediated constriction and dilation in rat middle cerebral arteries

Neuropeptide Y (NPY) is an important vasoconstrictor in the cerebral circulation. Its constrictor response is because of activation of NPY receptors on the vascular smooth muscle (VSM). Little is known regarding the effects of NPY on the endothelium. In the current study, the authors tested the hypothesis that NPY can either constrict or dilate rat middle cerebral arteries (MCAs). Constriction is elicited by stimulating receptors on the VSM; dilation is elicited by stimulating receptors on the endothelium. Middle cerebral arteries were isolated, cannulated with micropipettes, pressurized to 85 mm Hg, and luminally perfused. The extraluminal application of NPY (mixed agonist), [Leu31, Pro34]-NPY (Y1 agonist), or NPY-[13-36] (Y2 agonist) produced concentration-dependent constrictions. BIBP 3226 (Y1 selective antagonist) significantly attenuated the NPY- and [Leu31, Pro34]-NPY-induced constrictions. The luminal application of NPY, [Leu31, Pro34]-NPY, and NPY-[13-36] produced concentration-dependent dilations of MCAs. The maximum dilation produced by the NPY receptor agonists was approximately 40% of the dilation elicited by the luminal administration of 10(-5) mol/L ATP. Dilations elicited by luminal NPY, [Leu31, Pro34]-NPY, or NPY-[13-36] were abolished by inhibition of nitric oxide synthase with 10(-5) mol/L Nomega-nitro-L-arginine methyl ester (L-NAME) or removal of the endothelium. Dilations produced by luminal NPY or luminal [Leu31, Pro34]-NPY were not affected by BIBP 3226. Stimulation of NPY receptors on vascular smooth muscle constricted MCAs. Stimulation of an NPY receptor other than the Y1 subtype on endothelium dilated the MCAs by releasing nitric oxide.

Protamine-modified DDAB lipid vesicles promote gene transfer in the presence of serum

Cationic lipid vesicle-mediated gene transfer has become common for in vitro gene delivery. However, the transfection efficiency is often impaired by serum. DDAB (dimethyldioctadecyl ammonium bromide) lipid vesicle-mediated gene transfer, which we previously reported, has the same problem. To overcome this obstacle, we here report a novel transfection vehicle using protamine-modified DDAB lipid vesicles. While free protamine was simply added to the DNA/lipid complex in the previous study, in the present method the protamine is chemically conjugated to stearic acid and incorporated into DDAB lipid vesicles. Gene transfer was not significantly inhibited in 10% serum-containing medium by this method for the transfection of cultured cells. Protamine-modified DDAB lipid vesicles also enhanced virus transduction efficiency in the presence of serum using a replication-defective retroviral vector. Furthermore, the vesicles allowed efficient gene transfer for avian embryos in vivo. These results indicate that the method is useful for the production of transgenic animals and gene therapy.

[High temperature Raman spectroscopic study of the structure of sodium disilicate crystal, glass and its melt]

The structure of Na2Si2O5 from room temperature up to 1,773 K are studied by high temperature Raman spectroscopy using copper vapor pulse laser and integral time-resolved detection technique without any black-body radiation effect on spectral record. Back-scattering optical configuration is coupled with confocal collection of Raman signal of macro-sample in the high temperature shaft tube furnace. Results show that temperature-dependent Raman spectra can clearly indicate phase transition during melting. Relative densities of various kinds of SiO4(n-4) (n, bridging-oxygen number binding to one tetrahedron former Si) tetrahedrons can be qualitatively and quantitatively resolved by Gaussian spectral deconvolution. Obviously high temperature Raman spectroscopy provides an useful tool for the micro-structure research of materials under high temperature.

Activation of the IkappaB kinase complex by TRAF6 requires a dimeric ubiquitin-conjugating enzyme complex and a unique polyubiquitin chain

TRAF6 is a signal transducer in the NF-kappaB pathway that activates IkappaB kinase (IKK) in response to proinflammatory cytokines. We have purified a heterodimeric protein complex that links TRAF6 to IKK activation. Peptide mass fingerprinting analysis reveals that this complex is composed of the ubiquitin conjugating enzyme Ubc13 and the Ubc-like protein Uev1A. We find that TRAF6, a RING domain protein, functions together with Ubc13/Uev1A to catalyze the synthesis of unique polyubiquitin chains linked through lysine-63 (K63) of ubiquitin. Blockade of this polyubiquitin chain synthesis, but not inhibition of the proteasome, prevents the activation of IKK by TRAF6. These results unveil a new regulatory function for ubiquitin, in which IKK is activated through the assembly of K63-linked polyubiquitin chains.

Electronic and vibrational spectra of a series of substituted carbazole derivatives

The FTIR and FTR spectra of halogen (Cl, Br, I) substituted carbazole and their N-acetic and propionic acids have been recorded. A number of lines have been assigned on the basis of previous studies on the parent compound and by comparisons with the characteristic vibrations of their constituent structural units as well as comparing the spectra from FTIR and FTR. Some substituent-sensitive bands and characteristic bands were found. The electronic absorption spectra of these compounds in acetonitrile were also measured and are briefly discussed.

[High temperature Raman spectra and micro-structure study of lithium metaborate and its melt]

Lithium metaborate (LiBO2) is studied by high temperature Raman spectroscopy from room temperature up to 1,673 K, and spectra drawing in different temperature are got. By analyzing, it focus on the phase transition, it is that the endless chains of BO3 triangles transform into rings of (B3O6)3- at about 1,123 K, and then the different kind of phase balance's motion occurs after 1,273 K which implies that both endless chain and ring have changed to CRN. In the drawing, the variation of peak's area rate implies the micro-structure information, and shows the process from order to disorder.

[Effect of mouse p53 minigene on lung cancer cells with different 172 structures regulated by tetracycline]

OBJECTIVE

To investigate the effect of mouse 172 wild-type p53 (Arg), pseudo-wild-mutant-type p53 (Arg-->Leu) and mutant-type p53 (Arg-->His) induced by absence of tetracycline on the growth of PG cell line.

METHODS

Three variant types of p53 minigene were sub-cloned by gene recombination into an expression vector which was controlled by tetracycline. Through LipofectAMINE, the vectors were transfected into p53 defective PG (248CGG-->CTT) cells, and the transfectants were screened in the selecting medium containing puromycin. Tumor suppressing effects were studied by MTT absorption, flow cytometry and Western blotting.

RESULTS

Wild-type p53 and pseudo-wild-mutant-type p53 could lead cells to decrease their growth rates, arrest cell cycle and transactivation of p21(WAF1). Mutant-type p53 was defective in tumor suppression.

CONCLUSION

Wild-type p53 and pseudo-wild-type p53 may inhibit cell growth and induce cell cycle arrest. Some p53 variants such as 172 Arg-->Leu can still retain the tumor suppression function of the wild-type.

[Inhibition of growth and metastasis of human giant cell carcinoma of the lung by transfection of antisense VEGF121 cDNA]

OBJECTIVE

To explore the effects of blocking the VEGF/VEGF receptor paracrine pathway on growth and metastasis of human lung carcinoma cell line PG and to evaluate its potential application in gene therapy of cancer.

METHODS

The eukaryotic expression vectors bearing either sense-VEGF121 cDNA or antisense-VEGF121 cDNA was constructed and transfected into PG cells. In vitro and in vivo tests such as Northern blotting hybridization, Western blotting immunochemistry analysis, as well as xenografting in nude mice were used to analyze the effect of antisense-VEGF.

RESULTS

The transfectants stably expressing antisense VEGF121 were observed to produce markedly reduced 3.3 kb VEGF mRNA and 45 KD, 41 KD, 32KD VEGF proteins. When xenografted s.c. into nude mice, growth and metastasis of the antisense-VEGF transfected cell lines were greatly inhibited when compared with control cells.

CONCLUSION

Antisense VEGF gene significantly inhibited tumor growth and metastasis and may provide an experimental example for the development of antiangiogenic gene therapy.

[Clinical and experimental study on treatment of infantile autumn diarrhea by retention enema with Qilian liquid]

OBJECTIVE

To find out the effective treatment for infantile autumn diarrhea (IAD).

METHODS

Retention enema with Qilian Liquid (QLL) was applied to the patients of IAD with positive antigen of rotavirus in stool, and the clinical effect in the treated group was compared with that in the control group in aspects of negative conversion rate of rotavirus and change of immunoglobulin. Animal experimental study was also conducted.

RESULTS

The disappearance time of principal symptoms, negative conversion rate of rotavirus and serum levels of IgA and IgG in the treated group were significantly higher than those in the control group (P < 0.01, P < 0.05). Experimental study showed that QLL not only has the the anti-viral effects to stop diarrhea, but also has effects in enhancing immune function and protecting intestinal mucous membrane.

CONCLUSION

Retention enema with QLL is an effective therapy for the treatment of IAD.

Substrate deformation levels associated with routine physical activity are less stimulatory to bone cells relative to loading-induced oscillatory fluid flow

Although it is well accepted that bone tissue metabolism is regulated by external mechanical loads, it remains unclear to what load-induced physical signals bone cells respond. In this study, a novel computer-controlled stretch device and parallel plate flow chamber were employed to investigate cytosolic calcium (Ca2+i) mobilization in response to a range of dynamic substrate strain levels (0.1-10 percent, 1 Hz) and oscillating fluid flow (2 N/m2, 1 Hz). In addition, we quantified the effect of dynamic substrate strain and oscillating fluid flow on the expression of mRNA for the bone matrix protein osteopontin (OPN). Our data demonstrate that continuum strain levels observed for routine physical activities (< 0.5 percent) do not induce Ca2+i responses in osteoblastic cells in vitro. However, there was a significant increase in the number of responding cells at larger strain levels. Moreover, we found no change in osteopontin mRNA level in response to 0.5 percent strain at 1 Hz. In contrast, oscillating fluid flow predicted to occur in the lacunar-canalicular system due to routine physical activities (2 N/m2, 1 Hz) caused significant increases in both Ca2+i and OPN mRNA. These data suggest that, relative to fluid flow, substrate deformation may play less of a role in bone cell mechanotransduction associated with bone adaptation to routine loads.

[Expression of thrombospondin-1 and CD44 in human lung cancer tissues and their prognostic significance]

BACKGROUND

To analyze the expression of CD44H , CD44V6 and TSP-1 in human lung cancer tissues and their prognostic significance.

METHODS

A total of 112 lung cancer samples were examined for CD44H , CD44V6 and TSP-1 expression by immunohistochemical staining. Moreover , 25 cases out of them were detected for TSP-1 by RT-PCR assay simultaneously.

RESULTS

Stronger expression of TSP-1 was demonstrated in adenocarcinomas (74. 36 %) as compared with squamous cell carcinomas (47. 17 % , P = 0. 03) and small cell lung cancer (35. 71 % , P = 0. 02) . All of small cell lung cancer had significantly low expression of CD44H and CD44V6. Adenocarcinomas (61. 54 %) showed stronger CD44H membranous expression than squamous cell carcinomas did (50. 94 % , P = 0. 036) . Whereas , squamous cell carcinomas (50. 94 %) showed stronger CD44V6 membranous expression than adenocarcinomas did (17. 95 % , P = 0. 003) . Kaplan-Meier survival statistical analysis for 100 cases with complete follow-up data indicated that there was no significant relationship among TSP-1 , CD44H , CD44V6 expression and overall survival rate. However , after stratifying by histopathological types , the overall survival rate of patients with low expression of TSP-1 was significantly higher than that of moderate/ high expression groups in adenocarcinomas (Log Rank= 0. 0163) . Immunohistochemical and RT-PCR technique were utilized in 25 out of 112 cases simultaneously. The accordance rate of the two methods was 84 % , and no significant difference was found between them.

CONCLUSIONS

The expression of TSP-1 , CD44H and CD44V6 is significantly related to histopathological types. TSP-1 expression might be a prognostic indicator in lung adenocarcinoma. TSP-1 can be detected reliably in formalin-fixed , paraffin-embedded tissues by immunohistochemical method.

[The effects of cyclin E on the growth and other cell cycle related genes of breast carcinoma cells MCF-7]

OBJECTIVE

To investigate the effects of cyclin E in high and low expression on the cell growth and other cell cycle associated genes of MCF-7 cells.

METHODS

Eukaryotic expression vehicles of sense and antisense cyclin E were constructed and transferred into the MCF-7 cell line using lipofectAMINE. The integration and expression of cyclin E were conformed by Southern and Western blot. The cells growth was observed and the changes in cell cycle were analyzed by flow cytometry. The expression of other cell cycle associated genes was assayed using Western blot.

RESULTS

A high expression of cyclin E enabled to promote the cell growth and DNA synthesis and accelerated the proceeding of G(1) phase to S phase, It also promoted the phosphorylatin of pRB and up-regulate the expression of p27 while a low expression of cyclin E showed an opposite effect.

CONCLUSION

Different expression of cyclin E enables to affect growth of MCF-7 cell by the changes of cell cycle related genes.

[Developments of high temperature Raman spectroscopic techniques]

High temperature Raman spectroscopy (HTRS) is contemporarily a useful tool to study micro-structure of various materials under high temperature. Developments of HTRS techniques are well reviewed. In order to realize the determinations of metallurgical melts, the modified instrumentation for high temperature determination purpose based on JY U1000 Raman spectrometer in Shanghai Enhanced Lab of Ferrometallurgy (SELF) is introduced. It is assembled as macro-Raman with time-resolved detect system by using pulsed Copper Vapor Laser(CVL). This is the first set of its kind in domestic and some further modifications are proposed.

Observation of the cabibbo-suppressed decay xi(+)(c) --> pK(-)pi(+)

We report the first observation of the Cabibbo-suppressed charm baryon decay Xi(+)(c)-->pK(-)pi(+). We observe 150+/-22+/-5 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Sigma(-) beam. The branching fractions of the decay relative to the Cabibbo-favored Xi(+)(c)-->Sigma+K-pi(+) and Xi(+)(c)-->Xi(-)pi(+)pi(+) are measured to be B(Xi(+)(c)-->pK(-)pi(+))/B(Xi(+)(c)-->Sigma+K-pi(+)) = 0.22+/-0. 06+/-0.03 and B(Xi(+)(c)-->pK(-)pi(+))/B(Xi(+)(c)-->Xi(-)pi(+)pi(+)) = 0.20+/-0.04+/-0.02, respectively.

A wavelet-based coarse-to-fine image matching scheme in a parallel virtual machine environment

We present a wavelet-based, high performance, hierarchical scheme for image matching which includes (1) dynamic detection of interesting points as feature points at different levels of subband images via the wavelet transform, (2) adaptive thresholding selection based on compactness measures of fuzzy sets in image feature space, and (3) a guided searching strategy for the best matching from coarse level to fine level. In contrast to the traditional parallel approaches which rely on specialized parallel machines, we explored the potential of distributed systems for parallelism. The proposed image matching algorithms were implemented on a network of workstation clusters using parallel virtual machine (PVM). The results show that our wavelet-based hierarchical image matching scheme is efficient and effective for object recognition.

[Study on magnesium ionization in cathodic sputtering glow discharge plasma]

A method, based on the Doppler broadening-dependent absorption width and the ionization degree measured by the ratio of relative atomic and ionic absorbance in cathodic sputtering glow discharge (CSGD) plasma with aluminum-magnesium alloys as cathodes, is proposed. The experimental reveals that the plentiful magnesium ions in the plasma under the conventional discharge conditions of the atomizer do influence the analytic working curves. Corrected method is derived and factors which result in magnesium ionization degree are disscused.

[The establishment and application of genomic DNA extraction from peripheral blood]

OBJECTIVE

To establish the method of genomic DNA extraction.

METHODS

Genomic DNA was directly extracted from peripheral blood with the use of potassium iodide.

RESULTS

The genomic DNA extracted with potassium iodide was of large molecular weight. A(260)/A(280) and A(260)/ A(230) were 1.85 and 2.2 respectively. The extraction efficiency was greater than 90%. The result of PCR for the DNA was good.

CONCLUSION

The method is simple, quick, economical and could be used for studying numbers of clinical samples.

Interaction with members of the heterochromatin protein 1 (HP1) family and histone deacetylation are differentially involved in transcriptional silencing by members of the TIF1 family

Mammalian TIF1alpha and TIF1beta (KAP-1/KRIP-1) are related transcriptional intermediary factors that possess intrinsic silencing activity. TIF1alpha is believed to be a euchromatic target for liganded nuclear receptors, while TIF1beta may serve as a co-repressor for the large family of KRAB domain-containing zinc finger proteins. Here, we report an association of TIF1beta with both heterochromatin and euchromatin in interphase nuclei. Co-immunoprecipitation of nuclear extracts shows that endogenous TIF1beta, but not TIF1alpha, is associated with members of the heterochromatin protein 1 (HP1) family. However, in vitro, both TIF1alpha and TIF1beta interact with and phosphorylate the HP1 proteins. This interaction involves a conserved amino acid motif, which is critical for the silencing activity of TIF1beta but not TIF1alpha. We further show that trichostatin A, an inhibitor of histone deacetylases, can interfere with both TIF1 and HP1 silencing. The silencing activity of TIF1alpha appears to result chiefly from histone deacetylation, whereas that of TIF1beta may be mediated via both HP1 binding and histone deacetylation.

A genetic map and recombination parameters of the human malaria parasite Plasmodium falciparum

Genetic investigations of malaria require a genome-wide, high-resolution linkage map of Plasmodium falciparum. A genetic cross was used to construct such a map from 901 markers that fall into 14 inferred linkage groups corresponding to the 14 nuclear chromosomes. Meiotic crossover activity in the genome proved high (17 kilobases per centimorgan) and notably uniform over chromosome length. Gene conversion events and spontaneous microsatellite length changes were evident in the inheritance data. The markers, map, and recombination parameters are facilitating genome sequence assembly, localization of determinants for such traits as virulence and drug resistance, and genetic studies of parasite field populations.

[The role of NF-kappa B in the TNF-alpha-induced endothelial cell apoptosis]

OBJECTIVE

To investigate whether TNF-alpha could activate the signaling pathway-NF-kappa B/I-kappa B alpha required for the expression of inducible nitric oxide synthase (iNOS) to induce endothelial cell apoptosis by nitric oxide (NO).

METHODS

Aminoguanidine (AG, an inhibitor of iNOS) and Pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-kappa B) were evaluated for their influence on the apoptosis of cultured bovine pulmonary artery endothelial cells (BPAEC) induced by TNF-alpha. Apoptosis was confirmed by morphology, ultrastructural observation, agarose gel electrophoresis of DNA, and percentage of DNA fragmentation. Western blot analyses were used to detect the expression of iNOS and the levels of I-kappa B alpha in BPAEC exposed to TNF-alpha. Electrophoretic mobility shift assays (EMSA) were used to determinate the activity of NF-kappa B in BPAEC.

RESULTS

TNF-alpha induced BPAEC apoptosis (18.0 +/- 4.3)% in a concentration- and time-dependent manner. Both AG and PDTC attenuated the apoptosis of BPAEC induced by TNF-alpha, with peventages of DNA fragmentation in 2, 4, 10 mmol/L AG being (10.0 +/- 2.2)%, (7.8 +/- 1.2)% and (8.2 +/- 1.3)% vespectively. In BPAEC after TNF-alpha exposure, Western blot analyses revealed the expression of iNOS and the decrease in I-kappa B alpha. EMSA demonstrated an impermanency increase in NF-kappa B binding activity.

CONCLUSIONS

TNF-alpha can induce endothelial cell apoptosis by NO, which is produced by increasing iNOS expression and activating the signal pathway-NF-kappa B.

Construct for high-level expression and low misincorporation of lysine for arginine during expression of pET-encoded eukaryotic proteins in Escherichia coli

The arginine codon AGA is rarely used in E. coli but is common in eukaryotic genes. Prior studies have shown that the low level of tRNA(UCUArg) can lead to low expression and misincorporation of lysine for arginine, during expression of genes containing AGA codons in E. coli. The chloramphenicol-selectable plasmid pJY2 is designed to facilitate the expression of such genes cloned into pET vectors: it encodes T7 lysozyme (to depress constitutive expression of the cloned gene) and tRNA(UCUArg) (to suppress lysine misincorporation at AGA codons). Using pJY2, we observed robust and translationally faithful expression of mutant ubiquitin genes in which 14% (11 out of 76) of the total codons were AGA. Competent BL21(DE3)pJY2 cells can be used to suppress lysine misincorporation and achieve high-level expression of pET-encoded target genes without modification of AGA codons in the target gene sequence.

[Isolation and characterization of human prostate cancer cell subclones with different metastatic potential]

OBJECTIVE

To isolate and characterize cancer cell subclones with different metastatic potential from human metastatic prostate cancer cell line (PC-3M).

METHODS

Using limited dilution, in vitro growth, Matrigel invasion assay, soft agar cloning and in vivo tumorigenicity and spontaneous metastasis assay in nude mice, were isolated and characterized four subclones with different metastatic potential.

RESULTS

Four subclones derived from PC-3M were 1E8, 2E7, 2B6, 2B4. Each subclone exhibited a different metastatic potential when inoculated into nude mice. Among these subclones, 1E8 expressed as the highly metastatic phenotype, with 100% metastasis frequency 5 weeks after subcutaneous inoculation into nude mice, whereas 2B4 was not metastatic. In vitro 1E8 was found to be the most highly invasive cell line in Matrigel invasive assay (98 +/- 24) and had the most clones in soft agar cloning assay (265 +/- 39) while 2B4 was found to have the least invasive abilities (12 +/- 4) and the least clones (137 +/- 14).

CONCLUSION

Successful establishment of these subclones with different metastatic potential may be valuable for further study on the molecular mechanisms of cancer metastasis and cloning of cancer metastasis-related genes.

E2/E3-mediated assembly of lysine 29-linked polyubiquitin chains

Polyubiquitin (Ub) chains linked through Lys-48-Gly-76 isopeptide bonds represent the principal signal by which substrates of the Ub-dependent protein degradation pathway are targeted to the 26 S proteasome, but the mechanism(s) whereby these chains are assembled on substrate proteins is poorly understood. Nor have assembly mechanisms or definitive functions been assigned to polyubiquitin chains linked through several other lysine residues of ubiquitin. We show that rabbit reticulocyte lysate harbors enzymatic components that catalyze the assembly of unanchored Lys-29-linked polyubiquitin chains. This reaction can be reconstituted using the ubiquitin-conjugating enzyme (E2) known as UbcH5A, a 120-kDa protein(s) that behaves as a ubiquitin-protein ligase (E3), and ubiquitin-activating enzyme (E1). The same partially purified E3 preparation also catalyzes the assembly of unanchored chains linked through Lys-48. Kinetic studies revealed a K(m) of approximately 9 microM for the acceptor ubiquitin in the synthesis of diubiquitin; this value is similar to the concentration of free ubiquitin in most cells. Similar kinetic behavior was observed for conjugation to Lys-48 versus Lys-29 and for conjugation to tetraubiquitin versus monoubiquitin. The properties of these enzymes suggest that there may be distinct pathways for ubiquitin-ubiquitin ligation versus substrate-ubiquitin ligation in vivo.

Functional heterogeneity of endothelial P2 purinoceptors in the cerebrovascular tree of the rat

The effects of stimulating P2Y1 or P2Y2 purinoceptors on the endothelium of isolated middle cerebral arteries (MCAs), third-order branches of the MCA (bMCAs), and penetrating arterioles (PAs) of the rat were studied. After pressurization and development of spontaneous tone (25% contraction), resting diameters for MCAs, bMCAs, and PAs were 203 +/- 5 (n = 50), 99 +/- 2 (n = 42), and 87 +/- 2 micron (n = 53), respectively. Luminal application of the P2Y1-selective agonist 2-methylthioadenosine 5'-triphosphate elicited dose-dependent dilations (or loss of intrinsic tone) in MCAs but not in bMCAs or PAs. The dilation in MCAs was completely blocked by removal of the endothelium or by nitro-L-arginine methyl ester (10(-5) M), an inhibitor of NO synthase. Luminal application of the P2Y2-selective agonist ATP elicited dilations in MCAs, bMCAs, and PAs. Removal of the endothelium abolished the dilations in all vessel groups. Dilations in MCAs have been shown to involve both NO and endothelium-derived hyperpolarizing factor (EDHF). The dilations in bMCAs and PAs had a minor NO component and prominent EDHF component; that is, 1) the dilations to ATP were not diminished by the combined inhibition of NO synthase and cyclooxygenase, 2) the dilations were accompanied by significant hyperpolarizations of the vascular smooth muscle (approximately 15 mV), and 3) the dilations were completely abolished by the calcium-activated potassium channel blocker charybdotoxin. We concluded that the role of NO in purinoceptor-induced dilations diminishes along the cerebrovascular tree in the rat, whereas the role of EDHF becomes more prominent.

Chromosome size-dependent control of meiotic reciprocal recombination in Saccharomyces cerevisiae: the role of crossover interference

In the yeast Saccharomyces cerevisiae, small chromosomes undergo meiotic reciprocal recombination (crossing over) at rates (centimorgans per kilobases) greater than those of large chromosomes, and recombination rates respond directly to changes in the total size of a chromosomal DNA molecule. This phenomenon, termed chromosome size-dependent control of meiotic reciprocal recombination, has been suggested to be important for ensuring that homologous chromosomes cross over during meiosis. The mechanism of this regulation was investigated by analyzing recombination in identical genetic intervals present on different size chromosomes. The results indicate that chromosome size-dependent control is due to different amounts of crossover interference. Large chromosomes have high levels of interference while small chromosomes have much lower levels of interference. A model for how crossover interference directly responds to chromosome size is presented. In addition, chromosome size-dependent control was shown to lower the frequency of homologous chromosomes that failed to undergo crossovers, suggesting that this control is an integral part of the mechanism for ensuring meiotic crossing over between homologous chromosomes.

Image/patient registration from (partial) projection data by the Fourier phase matching method

A technique for 2D or 3D image/patient registration, PFPM (projection based Fourier phase matching method), is proposed. This technique provides image/patient registration directly from sequential tomographic projection data. The method can also deal with image files by generating 2D Radon transforms slice by slice. The registration in projection space is done by calculating a Fourier invariant (FI) descriptor for each one-dimensional projection datum, and then registering the FI descriptor by the Fourier phase matching (FPM) method. The algorithm has been tested on both synthetic and experimental data. When dealing with translated, rotated and uniformly scaled 2D image registration, the performance of the PFPM method is comparable to that of the IFPM (image based Fourier phase matching) method in robustness, efficiency, insensitivity to the offset between images, and registration time. The advantages of the former are that subpixel resolution is feasible, and it is more insensitive to image noise due to the averaging effect of the projection acquisition. Furthermore, the PFPM method offers the ability to generalize to 3D image/patient registration and to register partial projection data. By applying patient registration directly from tomographic projection data, image reconstruction is not needed in the therapy set-up verification, thus reducing computational time and artefacts. In addition, real time registration is feasible. Registration from partial projection data meets the geometry and dose requirements in many application cases and makes dynamic set-up verification possible in tomotherapy.

[Expression of membrane-type I matrix metalloproteinase and its correlation with gelatinase A activation in cancer cell lines]

OBJECTIVE

To study the expression of membrane-type I matrix metalloproteinase (MT1-MMP) and its correlation with gelatinase A (MMP2) activation.

METHODS

Reverse transcription PCR, northern blots and western blots were employed to detect the expression levels of MT1-MMP mRNA and MMP2 protein in 4 human melanoma cell lines, 2 human lung cancer cell lines and 2 human prostate cancer cell lines.

RESULTS

All the cancer cell lines expressed MT1-MMP mRNA, and the MT1-MMP mRNA level in the 4 melanoma cell lines was significantly higher than that in the lung and prostate cancer cell lines. Activated MMP2 proteins were only detected in the melanoma cell lines, whereas PG, a lung cancer cell line, which secreted pro-MMP2 and expressed low level of MT1-MMP, could not produce activated MMP2.

CONCLUSIONS

The level of MT1-MMP expression was highly associated with MMP2 activation.

Enhancement of transfection efficiency by protamine in DDAB lipid vesicle-mediated gene transfer

We have previously developed a simple gene transfection procedure mediated by cationic lipid vesicles for animal cells, in which a commercially available cationic surfactant, dimethyldioctadecyl ammonium bromide (DDAB), was used for making lipid vesicles. In the present study, we examined enhancement of transfection efficiency for this method by adding protamine to plasmid DNA solution before the formation of DNA/lipid vesicle complexes. Both free-base protamine and protamine sulfate provided enhanced transfection efficiency and expression level, but the optimal amount of the two protamines was different. The enhancement in transfection efficiency and expression level by protamines was observed in all the cell lines (COS-7, Hela, NIH3T3, MDCK, and BHK-21C13) and all the plasmids (pCMVbeta, pmiwZ, and pCH110) tested. The enhancement in both transfection efficiency and expression level was at most 20-fold compared with that using only DDAB lipid vesicles. Protamines seemed to protect DNA from degradation by DNase and promote DNA delivery into a nucleus.

P2u receptor-mediated release of endothelium-derived relaxing factor/nitric oxide and endothelium-derived hyperpolarizing factor from cerebrovascular endothelium in rats

BACKGROUND AND PURPOSE

Stimulation of P2u purinoceptors by UTP on endothelium dilates the rat middle cerebral artery (MCA) through the release of endothelium-derived relaxing factor/nitric oxide (EDRF/NO) and an unknown relaxing factor. The purpose of this study was to determine whether this unknown relaxing factor is endothelium-derived hyperpolarizing factor (EDHF).

METHODS

Rat MCAs were isolated, cannulated, pressurized, and luminally perfused. UTP was added to the luminal perfusate to elicit dilations.

RESULTS

Resting outside diameter of the MCAs in one study was 209+/-7 micrometer (n=10). The MCAs showed concentration-dependent dilations with UTP administration. Inhibition of NO synthase with NG-nitro-L-arginine methyl ester (L-NAME) (1 micromol/L to 1 mmol/L) did not diminish the maximum response to UTP but did shift the concentration-response curve to the right. Scavenging NO with hemoglobin (1 or 10 micromol/L) or inhibition of guanylate cyclase with ODQ (1 or 10 micromol/L) had effects on the UTP-mediated dilations similar to those of L-NAME. In the presence of L-NAME, dilations induced by 10 micromol/L UTP were accompanied by 13+/-2 mV (P<0.009) hyperpolarization of the vascular smooth muscle membrane potential (-28+/-2 to -41+/-1 mV). Iberiotoxin (100 nmol/L), blocker of the large-conductance calcium-activated K channels, sometimes blocked the dilation, but its effects were variable. Charybdotoxin (100 nmol/L), also a blocker of the large-conductance calcium-activated K channels, abolished the L-NAME-insensitive component of the dilation to UTP.

CONCLUSIONS

Stimulation of P2u purinoceptors on the endothelium of the rat MCA released EDHF, in addition to EDRF/NO, and dilated the rat MCA by opening an atypical calcium-activated K channel.

Application of the dual-micropipet technique to the measurement of tumor cell locomotion

The objective of this work was to characterize tumor cell locomotion in response to chemotactic stimulation using a dual-micropipet assay. The assay involves two micropipets. An individual A2058 human melanoma cell was retained, without pressure gradient, in a pipet of approximately 14 micrometers i.d. A solution of type IV collagen, chosen as the chemotactic source, was placed in another pipet (approximately 10 micrometers o.d.) with zero pressure at the pipet tip. The smaller pipet was then inserted into the larger one containing the melanoma cell. The initial chemoattractant concentration (C0) and the distance between the tip of the small pipet and the cell surface (delta) provided a gradient (C0/delta) for tumor cell locomotion toward stimulation. This novel assay provides a direct measure of cell movement: cyclic pseudopod protrusion (Lp) and subsequent cell locomotion (Lc). The influences of different adhesion substrates on cell locomotion were also studied. The peak length in Lp precedes the highest locomotion velocity (dLc/dt) by an apparent lag time. C0/delta influences pseudopod protrusion frequency (fp) and dLc/dt, but not significantly on Lp. Substrate adhesions affect dLc/dt, but apparently not Lp or fp. In conclusion, pseudopod protrusion and substrate adhesion are two necessary but mutually independent factors in tumor cell locomotion. dLc/dt correlates with changes in C0/delta, which is in significant correlation with fp but not Lp.

TIF1gamma, a novel member of the transcriptional intermediary factor 1 family

The Anaphase-Promoting Complex/Cyclosome (APC/C) is an ubiquitin ligase that functions during mitosis. Here we identify the transcriptional regulator, Transcriptional Intermediary Factor 1γ, TIF1γ as an APC/C-interacting protein that regulates APC/C function. TIF1γ is not a substrate for APC/C-dependent ubiquitylation but instead, associates specifically with the APC/C holoenzyme and Cdc20 to affect APC/C activity and progression through mitosis. RNA interference studies indicate that TIF1γ knockdown results in a specific reduction in APC/C ubiquitin ligase activity, the stabilization of APC/C substrates, and an increase in the time taken for cells to progress through mitosis from nuclear envelope breakdown (NEBD) to anaphase. TIF1γ knockdown cells are also characterized by the inappropriate presence of cyclin A at metaphase, and an increase in the number of cells that fail to undergo metaphase-to-anaphase transition. Expression of a siRNA-resistant TIF1γ species relieves the mitotic phenotype imposed by TIF1γ knockdown and allows for mitotic progression. Binding studies indicate that TIF1γ is also a component of the APC/C-Mitotic Checkpoint Complex (MCC), but is not required for MCC dissociation from the APC/C once the Spindle Assembly Checkpoint (SAC) is satisfied. TIF1γ inactivation also results in chromosome misalignment at metaphase, and SAC activation; inactivation of the SAC relieves the mitotic block imposed by TIF1γ knockdown. Together these data define novel functions for TIF1γ during mitosis and suggest that a reduction in APC/C ubiquitin ligase activity promotes SAC activation.

TIF1gamma, a novel member of the transcriptional intermediary factor 1 family

We report the cloning and characterization of a novel member of the Transcriptional Intermediary Factor 1 (TIF1) gene family, human TIF1gamma. Similar to TIF1alpha and TIF1beta, the structure of TIF1beta is characterized by multiple domains: RING finger, B boxes, Coiled coil, PHD/TTC, and bromodomain. Although structurally related to TIF1alpha and TIF1beta, TIF1gamma presents several functional differences. In contrast to TIF1alpha, but like TIF1beta, TIF1 does not interact with nuclear receptors in yeast two-hybrid or GST pull-down assays and does not interfere with retinoic acid response in transfected mammalian cells. Whereas TIF1alpha and TIF1beta were previously found to interact with the KRAB silencing domain of KOX1 and with the HP1alpha, MODI (HP1beta) and MOD2 (HP1gamma) heterochromatinic proteins, suggesting that they may participate in a complex involved in heterochromatin-induced gene repression, TIF1gamma does not interact with either the KRAB domain of KOX1 or the HP1 proteins. Nevertheless, TIF1gamma, like TIF1alpha and TIF1beta, exhibits a strong silencing activity when tethered to a promoter. Since deletion of a novel motif unique to the three TIF1 proteins, called TIF1 signature sequence (TSS), abrogates transcriptional repression by TIF1gamma, this motif likely participates in TIF1 dependent repression.

[Application of supercritical fluid extraction (SFE) on environmental analysis]

In this paper, publications from 1993 are classified according to the type of matrix from which the environmental analytes are extracted. Although the most applications of SFE are used for the solid, some analysts have concerned with aqueous and gaseous media. Various aspects of investigation of environmental potential carcinogen, such as, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, pesticides, phenols and other hazardous and toxic pollutants in environmental samples have been reviewed with 55 references. The coupled techniques of SFE have also been introduced in this paper.

A unified reconstruction framework for both parallel-beam and variable focal-length fan-beam collimators by a Cormack-type inversion of exponential radon transform

A variety of inversions of exponential Radon transform has been derived based on the circular harmonic transform in Fourier space by several research groups. However, these inversions cannot be directly applied to deal with the reconstruction for fan-beam or variable-focal-length fan-beam collimator geometries in single photon emission computed tomography (SPECT). In this paper, we derived a Cormack-type inversion of the exponential Radon transform by employing the circular harmonic transform directly in the projection space and the image space instead of the Fourier space. Thus, a unified reconstruction framework is established for parallel-, fan-, and variable-focal-length fan-beam collimator geometries. Compared to many existing algorithms, the presented one greatly mitigates the difficulty of image reconstruction due to the complicated collimator geometry and significantly reduces the computational burden of the special functions, such as Chebyshev or Bessel functions. By the well-established fast-Fourier transform (FFT), our algorithm is very efficient, as demonstrated by several numerical simulations.

[The protective role of heat shock gene expression on hydrogen peroxide induced pulmonary alveolar macrophages]

The aim of this study is to determine whether heat-induced heat shock gene expression in rat pulmonary alveolar macrophages (PAMs) would protect PAMs against hydrogen peroxide (H2O2)-mediated cell killing. In response to sublethal heat shock at 42 degrees C for 2 h, the cells synthesized heat shock protein 70 kD (HSP70) and other different molecular weight heat shock proteins, which were detected with gel electrophoresis after [35S]-methionin labeling cellular protein and Western blotting analysis in PAMs. Northern blot analysis showed the induction of HSP70 mRNA with heat shock treatment. Futhermore, with heat shock, there was a significant increment of survival cells after H2O2 (1,2,3 mmol.L-1, 45 min) exposure. This increase was blocked both by Cycloheximide and by Actinomycin D, and was associated with inhibition of synthesis of HSP70 protein and transcription of HSP70 mRNA. These results strongly suggest that expression of heat shock gene (especially HSP70 gene) plays an important role in the intracelluar mechanism of cytoprotection against H2O2 in rat PAMs.

A harmonic decomposition reconstruction algorithm for spatially varying focal length collimators

Spatially varying focal length fan-beam collimators can be used in single photon emission computed tomography to improve detection efficiency and to reduce reconstruction artifacts resulting from the truncation of projection data. It has been proven that there exists no convolution backprojection algorithm for this type of collimator, so a complicated interpolation between two nonparallel projection rays is necessary for existing algorithms. The interpolation may generate blurring and artifacts in the reconstructed images. Based on a harmonic decomposition technique and the translation property of Fourier series, a semifrequency resampling technique is proposed to avoid the above mentioned interpolations. By this technique, the harmonic decomposition of projection data for spatially varying focal length fan-beam collimators has the same form as that for parallel-beam collimators in the semifrequency domain (Fourier transform with respect to angular variables only). An alternative version of the inverse Cormack transform is then proposed to reconstruct the images. The derived reconstruction algorithm was implemented in a Pentium II/266 PC computer. Numerical simulations demonstrated its efficiency (3 s for 128 x 128 reconstruction arrays) and its robust performance (compared to the existing algorithms).

TIF1alpha: a possible link between KRAB zinc finger proteins and nuclear receptors

Ligand-induced gene activation by nuclear receptors (NRs) is thought to be mediated by transcriptional intermediary factors (TIFs), that interact with their ligand-dependent AF-2 activating domain. Included in the group of the putative AF-2 TIFs identified so far is TIF1alpha, a member of a new family of proteins which contains an N-terminal RBCC (RING finger-B boxes-coiled coil) motif and a C-terminal bromodomain preceded by a PHD finger. In addition to these conserved domains present in a number of transcriptional regulatory proteins, TIF1alpha was found to contain several protein-protein interaction sites. Of these, one specifically interacts with NRs bound to their agonistic ligand and not with NR mutants that are defective in the AF-2 activity. Immediately adjacent to this 'NR box', TIF1alpha contains an interaction site for members of the chromatin organization modifier (chromo) family, HP1alpha and MOD1, which both are heterochromatinic proteins. Finally, TIF1alpha also has a binding site for KRAB silencing domains of C2H2 zinc finger proteins. TIF1beta, another member of the TIF1 gene family, has some interacting partners in common with TIF1alpha. TIF1beta can interact with HP1alpha, MOD1 and KRAB domains, but apparently not with NRs. Both TIF1alpha and TIF1beta repress transcription when fused to a DNA binding domain in transiently transfected mammalian cells. A model discussing the potential function(s) of TIF1s in the control of transcription at the level of the chromatin template will be presented.