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W Fang

Publications and source records attributed to W Fang.

At least 19 recordsLinked to original sources
PubMed2005

Cloning of novel laccase isozyme genes from Trametes sp. AH28-2 and analyses of their differential expression.

Three novel laccase isozyme genes, lacA, lacB, and lacC, have been identified from basidiomycete Trametes sp. AH28-2. These genes display a high similarity with other basidiomycete laccases at the amino acid level. An inferred TATA box and several putative CAAT, MRE, XRE, and CreA consensus sequences were identified in the lacA, lacB, and lacC promoter regions. Different from the TATA boxes of lacA and lacB at about -100, the TATA box of lacC is located at -172. For all the isozymes, copper ion is essential for laccase synthesis in Trametes sp. AH28-2. More interestingly, different aromatic compounds can selectively induce the production of distinct laccase isozymes, with o-toluidine inducing the expression of laccase A (LacA) while 3,5-dihydroxytoluene mainly stimulating the production of laccase B (LacB). Quantitative reverse transcriptase-polymerase chain reaction showed that the accumulation of laccase messenger RNA transcripts is accompanied by the increase of corresponding enzyme activity in cultures. The glucose-repression effect on laccase expression in Trametes sp. AH28-2 was also observed. Furthermore, lower Cu2+ concentration (lower than 0.5 mM) can induce LacA and a novel laccase (LacC), and the latter will disappear when Cu2+ concentration is increased up to 1-2 mM. Upon induction by 3,5-dihydroxytoluene, the ratio of LacA to LacB decreased in the later phase of induction.

Amino Acid Sequence↗
PubMed2005

Changes in circulating mesenchymal stem cells, stem cell homing factor, and vascular growth factors in patients with acute ST elevation myocardial infarction treated with primary percutaneous coronary intervention.

OBJECTIVE: To investigate the spontaneous occurrence of circulating mesenchymal stem cells (MSC) and angiogenic factors in patients with ST elevation acute myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). DESIGN: In 20 patients with STEMI, blood samples were obtained on days 1, 3, 7, 14, 21, and 28 after the acute PCI. Fifteen patients with a normal coronary angiography formed a control group. MSC (CD45-/CD34-), plasma stromal derived factor 1 (SDF-1), vascular endothelial growth factor A (VEGF-A), and fibroblast growth factor 2 (FGF-2) were measured by multiparametric flow cytometry and enzyme linked immunosorbent assay (ELISA). RESULTS: Circulating CD45-/CD34- cells were significantly decreased on day 7 compared with day 3. Cell counts normalised one month after the acute onset of STEMI. The changes were mainly seen in patients with a large infarction. Plasma SDF-1 increased significantly from day 3 to day 28, and VEGF-A and FGF-2 increased significantly from day 7 to day 28. CONCLUSIONS: Spontaneous sequential fluctuations in MSC and the increase in vascular growth factor concentrations after STEMI suggest that the optimal time for additional stem cell therapy is three weeks after a myocardial infarction to obtain the maximum effects by stimulating endogenous growth factors on the delivered stem cells.

Angioplasty, Balloon, Coronary↗
PubMed2001

Hypermethylation in human cancers of the RIZ1 tumor suppressor gene, a member of a histone/protein methyltransferase superfamily.

The retinoblastoma protein-interacting zinc finger gene RIZ1 is a tumor suppressor gene and a member of a nuclear histone/protein methyltransferase superfamily. RIZ1 inactivation is commonly found in many types of human cancers and occurs through loss of mRNA expression, frameshift mutation, chromosomal deletion, and missense mutation. RIZ1 is also a tumor susceptibility gene in mice. We now show that loss of RIZ1 mRNA in human cancers is associated with DNA methylation of its promoter CpG island. Methylation of the RIZ1 promoter strongly correlated with lost or decreased RIZ1 mRNA expression in breast, liver, colon, and lung cancer cell lines as well as in liver cancer tissues. Treatment with the methylation inhibitor 5-aza-2'-deoxycytidine activated RIZ1 mRNA expression in cancer cells. Furthermore, methylation was found in 11 of 25 (44%) breast cancer specimens and 20 of 32 (62%) liver cancer specimens. Our results suggest that DNA methylation is a common mechanism in inactivating the RIZ1 tumor suppressor gene in human liver and breast cancers.

Animals↗
PubMed2001

Tumor formation and inactivation of RIZ1, an Rb-binding member of a nuclear protein-methyltransferase superfamily.

The retinoblastoma protein-interacting zinc finger gene RIZ (PRDM2) is a member, by sequence homology, of a nuclear protein-methyltransferase (MTase) superfamily involved in chromatin-mediated gene expression. The gene produces two protein products, RIZ1 that contains a conserved MTase domain and RIZ2 that lacks the domain. RIZ1 gene expression is frequently silenced in human cancers, and the gene is also a common target of frameshift mutation in microsatellite-unstable cancers. We now report studies of mice with a targeted mutation in the RIZ1 locus. The mutation inactivates RIZ1 but not RIZ2. These RIZ1 mutant mice were viable and fertile but showed a high incidence of diffuse large B-cell lymphomas (DLBL) and a broad spectrum of unusual tumors. RIZ1 deficiency also accelerated tumorigenesis in p53 heterozygous mutant mice. Finally, several missense mutations of RIZ1 were found in human tumor tissues and cell lines; one of these was particularly common in human DLBL tumors. These missense mutations, as well as the previously described frameshift mutation, all mapped to the MTase functional domains. All abolished the capacity of RIZ1 to enhance estrogen receptor activation of transcription. These data suggest a direct link between tumor formation and the MTase domain of RIZ1 and describe for the first time a tumor susceptibility gene among methyltransferases.

Alleles↗
PubMed2001

Preferential loss of a polymorphic RIZ allele in human hepatocellular carcinoma.

The RIZ (PRDM2) locus commonly undergoes loss of heterozygosity (LOH) and maps within the minimal deleted region on 1p36 in hepatocellular carcinoma (HCC). Although peptide-altering mutations of RIZ are rare in HCC, the RIZ1 product is commonly lost in HCC and has tumour suppressive activities. Here, we analysed RIZ gene mutations and LOH in HCC, breast cancer, familial melanoma, colon cancer, and stomach cancer. We found 7 polymorphisms but no mutations. By analysing the Pro704-deletion polymorphism, we detected LOH of RIZ in 31 of 79 (39%) informative HCC cases, 11 of 47 (23%) colon cancer cases, 8 of 43 (19%) breast cancer cases, 8 of 66 (12%) stomach cancer cases. Importantly, loss of the Pro704(+)allele was found in 74% of the 31 LOH positive HCC cases (P< 0.01), indicating a preferential loss and hence a stronger tumour suppressor role for this allele compared to the P704(-)allele. In addition, the Pro704(+)allele was found to be more common in Asians (0.61) than Caucasians (0.42) (P = 0.0000), suggesting an interesting link between gene polymorphisms and potential differences in tumour incidence between racial groups.

Alleles↗
PubMed2001

High-throughput, semi-automated determination of a cyclooxygenase II inhibitor in human plasma and urine using solid-phase extraction in the 96-well format and high-performance liquid chromatography with post-column photochemical derivatization-fluorescence detection.

Compound I, 5-chloro-3-(4-methanesulfonylphenyl)-6'-methyl-[2,3']bipyridinyl, has been found to be a specific inhibitor of the enzyme cyclooxygenase II (COX II). The anti-inflammatory properties of this compound are currently being investigated. HPLC assays for the determination of this analyte in human plasma and human urine have been developed. Isolation of I and the internal standard (II) was achieved by solid-phase extraction (SPE) in the 96-well format. A C8 SPE plate was used for the extraction of the drug from human plasma (recovery >90%) while a mixed-mode (C8/Cation) SPE plate was used to isolate the analytes from human urine (recovery approximately 71%). The analyte and internal standard were chromatographed on a Keystone Scientific Prism-RP guard column (20 x 4.6 mm) connected to a Prism-RP analytical column (150 x 4.6 mm), using a mobile phase consisting of 45% acetonitrile in 10 mM acetate buffer (pH = 4); the analytes eluted at retention times of 5.2 and 6.9 min for I and II, respectively. Compounds I and II were found to form highly fluorescent products after exposure to UV light (254 nm). Thus, the analytes were detected by fluorescence (lambda(ex) = 260 nm, lambda(em) =375 nm) following post-column photochemical derivatization. Eight point calibration curves over the concentration range of 5-500 ng/ml for human plasma and human urine yielded a linear response (R2>0.99) when a 1/y weighted linear regression model was employed. Based on the replicate analyses (n = 5) of spiked standards, the within-day precision for both assays was better than 7% C.V. at all points on the calibration curve; within-day accuracy was within 5% of nominal at all standard concentrations. The between-run precision and accuracy of the assays, as calculated from the results of the analysis of quality control samples, was better than 8% C.V. and within 8% of nominal. I was found to be stable in human plasma and urine for at least 8 and 2 months, respectively. In addition, the human plasma assay was semi-automated in order to improve sample throughput by utilizing a Packard liquid handling system and a Tom-Tec Quadra 96 SPE system. The precision and accuracy of the semi-automated procedure were comparable to the manual procedure. Over 5000 clinical samples have been analyzed successfully using these methods.

Automation↗
PubMed2001

Three-field lymph node dissection for esophageal cancer in elderly patients over 70 years of age.

BACKGROUND: The risk and benefit of esophagectomy with three-field lymph node dissection has not been well defined in elderly esophageal cancer patients. METHODS: A total of 441 patients underwent three-field lymph node dissection from 1986 to 1998. Patients were divided into two age groups: group 1 consisted of 79 patients aged 70 years or over, and group 2 consisted of 362 patients under 70 years of age. Patients' characteristics and surgical outcomes were compared between groups. Risk factors for morbidity, mortality, and survival of patients in group 1 were further studied by multivariate analysis. RESULTS: Significantly more patients had multiorgan dysfunction preoperatively in group 1 (24; 30.4%) than in group 2 (34; 9.4%, p < 0.001). The overall (65.8% vs 61.6%, p = 0.483) and surgically related complication rates (41.8% vs 52.2%, p = 0.093) were similar, but significantly more organ failure (11.4% vs 5.0%, p = 0.031) and infection (22.8% vs 13.8%, p = 0.045), defined as medical complications, occurred in group 1. There was no significant difference in 30-day (3.8% vs 0.8%, p = 0.074) or in-hospital mortality (7.6% vs 3.3%, p = 0.082) between groups. The overall (40.9% vs 48.1%, p = 0.235) and cause-specific 5-year survivals (55.4% vs 59.1%, p = 0.688) were comparably good in both groups, but the risk of death due to causes other than esophageal cancer was much higher in the elderly (p = 0.028). Multiorgan dysfunction was an independent predictive factor in elderly patients for overall and medical morbidity, overall survival, and risk of death from causes other than esophageal cancer. CONCLUSIONS: Esophagectomy with three-field lymph node dissection could be carried out safely in patients over 70 years of age with satisfactory long-term results. For elderly patients with multiorgan dysfunction, however, less invasive procedures might be more appropriate.

Age Factors↗
PubMed2001

Comparison of surgical management of thoracic esophageal carcinoma between two referral centers in Japan and China.

BACKGROUND: Comparison was made between two referral centers, the National Cancer Center Hospital (NCCH) in Japan and Shanghai Chest Hospital (SCH) in China. The aim was to detect the possible differences between surgical management of thoracic esophageal carcinoma in these two countries and to shed some light on how to improve the therapeutic outcomes at similar institutions. METHODS: A total of 98 patients (50 from NCCH and 48 from SCH) with squamous cell carcinoma of the thoracic esophagus treated by a single surgeon at either center during January 1997 to July 1999 were retrospectively reviewed. RESULTS: Lugol staining and endoscopic ultrasonography were applied routinely at NCCH only. More early diseases, multiple lesions and synchronous tumors of the digestive tract were detected in the NCCH group than in the SCH group. Significantly more stations of lymph nodes were dissected and higher metastatic rates to certain stations were found after more extensive lymphadenectomy in the NCCH group. Operation time was prolonged with significantly more postoperative complication but amount of blood loss or in-hospital mortality was not increased. There was a tendency toward better survival in the NCCH group at 2-year follow-up (70.9% NCCH vs. 56.2% SCH, p = 0.052). CONCLUSIONS: Lugol staining is useful in detecting early diseases or multiple lesions and endoscopic ultrasonography in increasing the knowledge of preoperative evaluation and thus should be recommended. Attention should be paid to more thorough lymph node dissection, especially those lymph node stations with high metastatic rates within the chest and the abdomen and meanwhile avoiding major postoperative complications, so as to improve further the accuracy of tumor staging and therapeutic outcome.

Carcinoma, Squamous Cell↗
PubMed2001

Clinical outcome of patients with previous myocardial infarction and left ventricular dysfunction assessed with myocardial (99m)Tc-MIBI SPECT and (18)F-FDG PET.

UNLABELLED: Myocardial viability was assessed by (99m)Tc-methoxyisobutylisonitrile (MIBI) SPECT and (18)F-FDG PET to evaluate the prognosis and treatment strategy of patients with myocardial infarction (MI) and left ventricular (LV) dysfunction. METHODS: One hundred twenty-three consecutive patients with previous MI and LV dysfunction (LV ejection fraction [EF], 35% +/- 6% [mean +/- SD]) who underwent (99m)Tc-MIBI SPECT and FDG PET were followed-up for 26 +/- 10 mo (mean +/- SD). Distributions of the 2 radiotracers in myocardial segments were classified into 2 patterns: myocardial perfusion-metabolism mismatch (MM) and match (M). LV EF and LV end-diastolic diameter (EDD) were measured by echocardiography at baseline, 3 mo (Pos1), and 6 mo (Pos2) after revascularization. Cardiac death, acute MI, unstable angina, and late revascularization (>3 mo) experienced by the patients during follow-up were defined as cardiac events. RESULTS: Sixty-seven patients underwent revascularization and 56 patients were treated medically. Of the 72 patients with > or =2 MM segments, 42 underwent revascularization (group A1) and 30 were treated medically (group A2). Of the 51 patients with <2 MM segments, 25 underwent revascularization (group B1) and 26 were treated medically (group B2). The 4 groups had similar baseline characteristics and rest LV EF. After revascularization, EF (mean +/- SD) increased in group A1 from 36% +/- 5% to 44% +/- 8% (P < 0.0001) in Pos1 and to 51% +/- 9% (P < 0.0001) in Pos2. EDD (mean +/- SD) decreased from 62 +/- 8 mm to 56 +/- 5 mm (P < 0.001) in Pos1 and to 55 +/- 5 mm (P < 0.001) in Pos2. However, EF and EDD were unchanged in group B1 (P > 0.05). During the follow-up, 22 patients (17.9%) suffered from cardiac events, including 11 cardiac deaths, 4 acute MI, 6 late coronary artery bypass grafting, and 1 unstable angina pectoris. The cardiac event rate in group A2 (50%) was significantly higher than that of groups A1 (2.4%; chi(2) = 23.08; P < 0.0001), B1 (12%; chi(2) = 8.94; P = 0.003), and B2 (11.5%; chi(2) = 9.45; P = 0.002). CONCLUSION: Assessment of myocardial viability using hybrid (99m)Tc-MIBI SPECT and FDG PET can predict the clinical outcome and is helpful to decision making in the treatment strategy of patients with MI and LV dysfunction. Revascularization can improve the LV function and clinical outcome of patients with >2 viable myocardial segments.

Aged↗
PubMed2001

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.

Animals↗
PubMed2001

Interferon-gamma inhibits in situ expression of PDGF-beta mRNA by smooth muscle cells in injured rabbit arteries after transluminal balloon angioplasty.

OBJECTIVE: To elucidate the mechanism of interferon-gamma (IFN-gamma) to inhibit the restenosis after successful percutaneous transluminal angioplasty (PTA). METHODS: A rabbit vascular restenotic model was constructed and the proliferation of intimal smooth muscle cells (SMCs) were observed by monitoring their expression of proliferating cell nuclear antigen (PCNA) and platelet-derived growth factor beta chain mRNA (PDGF-beta mRNA) at the indicated time points. RESULTS: IFN-gamma could significantly inhibit the expression of PCNA by intimal SMCs one week after denudation, when counting 200 intimal cells for PCNA-positive reactions with an inhibitory rate of 88.50% (P < 0.001). IFN-gamma could downregulate in situ expression of PDGF-beta mRNA by these cells as we calculated the average number of PDGF-beta mRNA positive cells per square millimetre area at x 400 magnification with reduced rates of 86.85% in 1 week group (P < 0.001), of 93.66% in 2 week group (P < 0.001) and of 52.92% in 4 week group (0.02 < P < 0.05), respectively. CONCLUSIONS: The local production of PDGF-beta by vascular intimal SMCs via an autocrine mechanism may be responsible for continuous proliferation of these cells and the formation of neointima after injury. This could be inhibited by IFN-gamma through downregulating the expression of PDGF-beta mRNA. These results provide an in vivo basis for IFN-gamma to be used clinically for the management of restenosis after percutaneous transluminal angioplasty.

Angioplasty, Balloon↗
PubMed2001

Clinical application of tentorium cerebelli hiatus incision in treatment of severe and most severe brain injuries.

OBJECTIVE: To explore the role of tentorium cerebelli hiatus incision in treating severe and most severe brain injuries complicated by tentorial herniation. METHODS: From July 1994 to July 1999 tentorium cerebelli hiatus incision was done based on intracranial hematoma evacuation and bone flap craniectomy decompression in 70 cases of severe and most severe brain injuries complicated by tentorial herniation. RESULTS: Of the 70 cases, GCS 3-5 was in 23 and GCS 6-8 in 47; satisfactory recovery in 39 cases (55.7%), moderate disability in 12 (17.1%), severe deficit in 6 (8.6%), vegetative survival in 4 (5.7%) and 8 (11.4%) died. CONCLUSIONS: Tentoriun cerebelli incision is helpful in alleviating secondary brain stem injury from tentorial herniation and in reducing the disability and death rate of the patients.

Adolescent↗
PubMed2001

[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.

Adenosine Triphosphate↗
PubMed2000

High-throughput simultaneous determination of the HIV protease inhibitors indinavir and L-756423 in human plasma using semi-automated 96-well solid phase extraction and LC-MS/MS.

A method for the simultaneous determination of the HIV protease inhibitors indinavir and L-756423, in human plasma has been developed. Plasma samples (0.5 ml) were extracted using a 3M Empore 96-well plate in the mixed phase cation exchange (MPC) format. The extraction method was automated through the application of both the Packard 204DT and TOMTEC Quadra 96 work stations, and the resulting extracts were analyzed using a PE-Sciex API-3000 LC-MS/MS with a heated nebulizer interface (500 degrees C). The assay was linear in the concentration range 1-2500 ng/ml for indinavir and 5 2500 ng/ml for L-756423 when 0.5-ml aliquots of plasma were extracted. Recoveries of indinavir and L-756423 were greater than 76 and 80%, respectively, over the calibration curve range when using the described sample preparation method. Within-batch precision and accuracy for the quantitation of indinavir over the range 1-2500 ng/ml were 5.4% R.S.D. or less and within 4.0%, respectively. Within-batch precision and accuracy for the quantitation of L-756423 over the range 5-2500 ng/ml were 5.3% R.S.D. or less and within 3.4%, respectively. Interbatch variability for the analysis of indinavir QC samples at low (3 ng/ml), middle (250 ng/ml) and high (2250 ng/ml) were 3.2, 2.9, and 1.9%, respectively. Interbatch variability for the analysis of L-756423 QC samples at low (15 ng/ml), middle (250 ng/ml) and high (2250 ng/ml) concentration were 2.0, 2.5, and 3.3%, respectively. The validated assay was used in support of human clinical trials.

Anti-HIV Agents↗
PubMed2000

Synthesis of benzo-fused 1-azabicyclo[m.n.0]alkanes via the Schmidt reaction: a formal synthesis of gephyrotoxin.

The intramolecular capture of benzocyclobutyl, benzocyclopentyl, and benzocyclohexyl carbocations 7 by azides produces spirocyclic aminodiazonium ions 8, which undergo 1,2-C-to-N rearrangement with loss of dinitrogen to produce benzo-fused iminium ions resulting from either aryl (9) or alkyl (10) migration to the electron-deficient nitrogen atom. Reduction of the iminium ions affords regioisomeric benzo-fused 1-azabicyclo[m.n.0]alkanes, e.g., benzopyrrolizidines, benzoindolizidines, benzoquinolizidines, or perhydrobenzo[f]pyrrolo[1,2-a]azepines in two regioisomeric versions, anilines (e.g., 11-14) and benzylic amines (e.g., 15-18), the result of aryl and alkyl migrations, respectively. Generally, aryl migration is preferred, despite modeling that shows that the lowest energy aminodiazonium ions are those where the departing dinitrogen is preferentially antiperiplanar to the migrating alkyl group rather than the aryl group. The utility of this methodology was illustrated by a formal synthesis of the alkaloid gephyrotoxin 4. A dependence on the efficiency and regioselectivity of the Schmidt reaction upon subtle changes in the structure of the cation precursor was observed, necessitating the exploration of a variety of substrates. Fortunately, these materials were easily made. Ultimately, the azido-alkene 81 bearing a 2-bromoethyl side-chain was useful for the Schmidt reaction, producing the known benzo-fused indolizidine 49, which had been transformed by Ito et al. into gephyrotoxin 4. The synthesis of 49 required nine steps (five purifications) from commercially available 4-methoxy-1-indanone 60 and proceeded in 22% overall yield.

Alkaloids↗
PubMed2000

Cdk2-dependent phosphorylation and functional inactivation of the pRB-related p130 protein in pRB(-), p16INK4A(+) tumor cells.

The retinoblastoma family proteins pRB, p107, and p130 are phosphorylated and released from E2Fs in the late G(1) phase of the cell cycle. This phosphorylation is thought to contribute to the derepression of E2F-responsive genes and to be mediated, in part, by Cdk4 and Cdk6. Evidence that Cdk4/6 activity is inhibited by p16(INK4A) in most pRB(-) cells suggests that p107 and p130 may be underphosphorylated and remain associated with E2Fs during G(1)-S progression in cells that lack pRB. To examine this, we evaluated the cell cycle-dependent phosphorylation and E2F binding abilities of p107 and p130 in pRB(-), p16(+) Saos-2 osteosarcoma cells. p130, but not p107, was phosphorylated and released from E2F-4 in late G(1) and S phase cells, although p130 phosphorylation differed qualitatively in these and other pRB(-), p16(+) cells as compared with pRB(+), p16(-) cell types. p130 phosphorylation occurred in the absence of cyclin D-Cdk4/6 complexes, coincided with cyclin E- and Cdk2-associated kinase activity, and was prevented by expression of dominant negative Cdk2. Moreover, dominant negative Cdk2 prevented the dissociation of endogenous p130-E2F-4 complexes and inhibited E2F-4-dependent transcription. These findings show that p130 can be phosphorylated and functionally inactivated in a Cdk2-dependent process, and they highlight the involvement of distinct Cdks in the regulation of different pRB family proteins.

CDC2-CDC28 Kinases↗
PubMed2000

Enhanced peroxidase activity in rice leaves in response to excess iron, copper and zinc.

The effect of excess Fe(2+) on the peroxidase (POD) activity in detached rice leaves was investigated. FeSO(4) was effective in stimulating POD activity in detached rice leaves under both light and dark conditions. FeSO(4) but not K(2)SO(4) induced POD activity, indicating that POD activity is induced by Fe(2+). FeSO(4)-induced POD activity is not specific for the rice cultivar used in this study. CuSO(4) and ZnSO(4) were also observed to induce POD activity in detached rice leaves. Cycloheximide blocked the enhanced activity of POD by Fe(2+), Cu(2+) or Zn(2+), indicating de novo biosynthesis of the enzyme. Paraquat treatment resulted in a decrease in POD activity. H(2)O(2) had no effect on POD activity in detached rice leaves. It seems that Fe(2+)-, Cu(2+)- or Zn(2+)-induced POD may not be mediated by free radicals. Using isoelectric focusing to separate POD, it was found that excess Fe(2+), Cu(2+) or Zn(2+) induced both quantitative and qualitative metal-specific changes in POD isozyme pattern in detached rice leaves. A new POD isozyme with a pI of 4.81 can be induced by Fe(2+), Cu(2+) and Zn(2+) in detached rice leaves.

Journal Article↗