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Ma J, Pollak MN, Giovannucci E, Chan JM, Tao Y, Hennekens CH, Stampfer MJ. Prospective study of colorectal cancer risk in men and plasma levels of insulin-like growth factor (IGF)-I and IGF-binding protein-3. J Natl Cancer Inst 1999; 91:620-5. [PMID: 10203281 DOI: 10.1093/jnci/91.7.620] [Citation(s) in RCA: 720] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Insulin-like growth factor-I (IGF-I) is a potent mitogen for normal and neoplastic cells, whereas IGF-binding protein-3 (IGFBP-3) inhibits cell growth in many experimental systems. Acromegalics, who have abnormally high levels of growth hormone and IGF-I, have higher rates of colorectal cancer. We therefore examined associations of plasma levels of IGF-I and IGFBP-3 with the risk of colorectal cancer in a prospective case-control study nested in the Physicians' Health Study. METHODS Plasma samples were collected at baseline from 14916 men without diagnosed cancer. IGF-I, IGF-II, and IGFBP-3 were assayed among 193 men later diagnosed with colorectal cancer during 14 years of follow-up and among 318 age- and smoking-matched control subjects. All P values are two-sided. RESULTS IGFBP-3 levels correlated with IGF-I levels (r=.64) and with IGF-II levels (r=.90). After controlling for IGFBP-3, age, smoking, body mass index (weight in kg/[height in m]2), and alcohol intake, men in the highest quintile for IGF-I had an increased risk of colorectal cancer compared with men in the lowest quintile (relative risk [RR]=2.51; 95% confidence interval [CI]=1.15-5.46; P for trend = .02). After controlling for IGF-I and other covariates, men with higher IGFBP-3 had a lower risk (RR=0.28; 95% CI=0.12-0.66; P for trend = .005, comparing extreme quintiles). The associations were consistent during the first and the second 7-year follow-up intervals and among younger and older men. IGF-II was not associated with risk. CONCLUSIONS Our findings suggest that circulating IGF-I and IGFBP-3 are related to future risk of colorectal cancer.
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Abstract
A procedure is described for reconstructing three-dimensional objects from two-dimensional projections. The method is based both on the original Crowther, DeRosier, and Klug (DeRosier, D.J., and Klug, A. (1968), Nature 217, 130-134; Crowther, R.A., DeRosier, D.J., and Klug, A. (1970) Proc. R. Soc. London A 317, 319-340) work on image reconstructions of icosahedral viruses and on the concept of noncrystallographic symmetry (Rossmann, M.G., 1995, Curr. Opin. Struct. Biol. 5, 650-655). The procedure has been applied so far only to test data where the objective has been the determination of particle orientation, both ab initio and through the use of model data.
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Abstract
The structure of the bluetongue virus core was recently reported and represents the largest structure determined to atomic resolution. As a biological machine capable of RNA transcription, the structure has immense biological significance.
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Kano M, Kawakami T, Hori H, Hashimoto Y, Tao Y, Ishikawa Y, Takenaka T. Effects of ALCAR on the fast axoplasmic transport in cultured sensory neurons of streptozotocin-induced diabetic rats. Neurosci Res 1999; 33:207-13. [PMID: 10211764 DOI: 10.1016/s0168-0102(99)00012-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of acetyl-L-carnitine (ALCAR) on fast axoplasmic transport were studied in cultured dorsal root ganglion (DRG) neurons of diabetic rats. Three-month-old male rats were used 7 days after streptozotocin injection. Neurons obtained from ganglia were cultured with a high concentration of glucose. The amount and the mean velocity of retrogradely transported particles, reduced in the diabetic animal, were transiently recovered by 1 mM ALCAR. The number of particles moving at 0.8-1.2 microm/s, considered to be lysosomes, increased in the velocity distribution. ALCAR did not modify the amount and mean velocity of anterograde particles which were unaffected by diabetes, or of bidirectional particles in neurons of control rats. This study suggests that diabetic neuropathy may be relieved by ALCAR via recovering retrograde axoplasmic transport.
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Xiao H, Tao Y, Roeder RG. The human homologue of Drosophila TRF-proximal protein is associated with an RNA polymerase II-SRB complex. J Biol Chem 1999; 274:3937-40. [PMID: 9933582 DOI: 10.1074/jbc.274.7.3937] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian RNA polymerase II holoenzymes are large complexes that have been reported to contain, in addition to RNA polymerase II, homologues of several yeast SRBs, various general transcription factors, and other polypeptides. On the basis of its copurification with an SRB-containing RNA polymerase II complex by conventional chromatography procedures, we have identified a human homologue of Drosophila TRF-proximal protein, designated hTRFP, and isolated its cognate cDNA. Antibody specific for SRB7 can immunoprecipitate hTRFP and RNA polymerase II and, reciprocally, antibody specific for hTRFP can immunoprecipitate RNA polymerase II and SRB7. These data indicate that hTRFP is an integral component of an RNA polymerase II-SRB complex. Whereas the precise function of hTRFP remains to be determined, the hTRFP-containing RNA polymerase II-SRB complex supports basal level transcription and, relative to RNA polymerase II alone, enhances transcriptional activation by Gal4-VP16 in the presence of cofactor PC4. Thus, hTRFP may regulate transcription of class II genes through association with the RNA polymerase II-SRB complex.
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306
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You X, Tao Y, Huang H, Gao Q, Cui Y. [Microwave therapy of radiotherapeutical choanal atresia under nasal endoscope]. LIN CHUANG ER BI YAN HOU KE ZA ZHI = JOURNAL OF CLINICAL OTORHINOLARYNGOLOGY 1999; 13:56-7. [PMID: 12564015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
OBJECTIVE In order to know efficacy of microwave to treat the secondary choanal atresia under nasal endoscope. METHOD Three patients suffering from membranous choanal atresia due to radiotherapy of nasopharyngeal carcinoma (NPC) were treated by microwave under nasal endoscope. RESULT Satisfing recoveries were accomplished in all patients and no relapse was found within the 7-13 months' follow-up. CONCLUSION This method has many advantages, such as: processing available under local anesthesia without incision, mild damage to normal tissues, clear operation visual field, less hemorrhage and postoperative pain, complete coagulation and gasification of atresic membrane, no need of postoperative dilation and stable therapeutical effect.
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307
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Huang Q, Tao Y, Yandell DW. [Mutations of several tumor suppressor genes in primary retinoblastoma]. ZHONGHUA ZHONG LIU ZA ZHI [CHINESE JOURNAL OF ONCOLOGY] 1999; 21:10-2. [PMID: 11776785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
OBJECTIVE To study the status of several tumor suppressor genes in primary retinoblastoma. METHODS Single stranded conformation polymorphism (SSCP) analysis associated with direct DNA sequencing was used to identify point mutations in the coding sequence of Rb, p53, p16, p15 and p21 tumor suppressor genes, and multiplex PCR was used to detect big deletion in p16 and p15 genes. RESULTS Rb gene point mutation was detected in 74% of retinoblastoma and p16 gene big deletions in 16% of retinoblastoma with or without Rb gene mutation. However, despite polymorphism, no real mutation was detected in p53 or p21 gene in retinoblastoma. CONCLUSION The evidence from this study suggests that retinoblastoma is resulted exclusively from alterations of genes in Rb pathway.
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Chen X, Yang Y, Tao Y. [Delayed brain injury induced by Bordetella pertussis in rats]. HUNAN YI KE DA XUE XUE BAO = HUNAN YIKE DAXUE XUEBAO = BULLETIN OF HUNAN MEDICAL UNIVERSITY 1998; 22:301-3. [PMID: 9868080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
To induced new model of delayed infection brain injury, we divided randomly 40 adult male Sprague-Dawley rats into four groups: bordetella pertussis (BP) groups, and normal sailine (NS) groups in 4 h (n = 10) and 24 h (n = 10), respectively, injected BP at 0.2 ml.kg-1 which contained the bacilli in 10.8 x 10(9).ml-1 into the rat left internal carotid artery of BP groups, and injected at the equal volume as control in the same way into NS groups. The water content (WC), Evans blue content (EB), cations of sodium, potassium, calcium in the brain tissues were measured and the morphologic changes in the hippocampal CA1 were detected by electron microscopy. These results were shown as follows: the left hemisphere of BP group in 4 h was characterized by the brain edema which predominated in swollen, necrotic astroglial cells, endothelial cells, and insignificant increase of contents of sodium, calcium and decrease of potassium; BP group in 24 h was characterized by dark cells, the brain edema also existed in astroglial cells. These results indicate that a delayed infection brain injury model is performed successfully by injection with BP into the left internal carotid artery of rats. The model is characterized by the features of delayed neuronal death and mixed type brain edema.
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Chen X, Yang Y, Du J, Tao Y, Cheng G. [Changes of NMDA receptor gene expression in infection brain injury induced by Bordetella pertussis in rats]. HUNAN YI KE DA XUE XUE BAO = HUNAN YIKE DAXUE XUEBAO = BULLETIN OF HUNAN MEDICAL UNIVERSITY 1998; 22:11-4. [PMID: 9868018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
N-methyl-D-aspartate receptors (NMDAR) in cerebral cortexes of rat brain injury induced by Bordetella pertussis (Bp) were measured by methods of Northern blot analysis and [3H] MK-801 radioligand-receptor binding to study changes and effects of NMDAR1 of gene expression in the infection brain injury. The affinity (Kd) of NMDAR in Bp group was significantly decreased [30.5 +/- 3.0 nmol.L-1 (Bp), 43.1 +/- 4.2 nmol.L-1 (NS), P < 0.05], but expression of NMDAR1 mRNA and binding site density (Bmax) of NMDAR observed no significant differences between the experimental and the control group (P > 0.05), respectively. The results suggest that NMDAR1 was activated with high affinity functionally, but no changes in binding site density and transcriptional expression of NMDAR1 occured in the infection brain injury.
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Martinez E, Ge H, Tao Y, Yuan CX, Palhan V, Roeder RG. Novel cofactors and TFIIA mediate functional core promoter selectivity by the human TAFII150-containing TFIID complex. Mol Cell Biol 1998; 18:6571-83. [PMID: 9774672 PMCID: PMC109242 DOI: 10.1128/mcb.18.11.6571] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/1998] [Accepted: 07/31/1998] [Indexed: 12/17/2022] Open
Abstract
TATA-binding protein-associated factors (TAFIIs) within TFIID control differential gene transcription through interactions with both activators and core promoter elements. In particular, TAFII150 contributes to initiator-dependent transcription through an unknown mechanism. Here, we address whether TAFIIs within TFIID are sufficient, in conjunction with highly purified general transcription factors (GTFs), for differential core promoter-dependent transcription by RNA polymerase II and whether additional cofactors are required. We identify the human homologue of Drosophila TAFII150 through cognate cDNA cloning and show that it is a tightly associated component of human TFIID. More importantly, we demonstrate that the human TAFII150-containing TFIID complex is not sufficient, in the context of all purified GTFs and RNA polymerase II, to mediate transcription synergism between TATA and initiator elements and initiator-directed transcription from a TAFII-dependent TATA-less promoter. Therefore, TAFII-promoter interactions are not sufficient for the productive core promoter-selective functions of TFIID. Consistent with this finding, we have partially purified novel cofactor activities (TICs) that potentiate the TAFII-mediated synergism between TATA and initiator elements (TIC-1) and TAFII-dependent transcription from TATA-less promoters (TIC-2 and -3). Furthermore, we demonstrate an essential function for TFIIA in TIC- and TAFII-dependent basal transcription from a TATA-less promoter. Our results reveal a parallel between the basal transcription activity of TAFIIs through core promoter elements and TAFII-dependent activator function.
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Gao Q, Liu Z, Tao Y. [Nasal packing and packing materials chosing after ESS (with clinical analysis of 769 cases)]. LIN CHUANG ER BI YAN HOU KE ZA ZHI = JOURNAL OF CLINICAL OTORHINOLARYNGOLOGY 1998; 12:493-5. [PMID: 11263221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Nasal packing after endoscopic sinus surgery is an important factor affecting the outcome of the operation. In order to discuss the clinical effect of no packing method and packing with different materials, we summarized our six years packing experiences of 769 cases (993 nasal cavities) undergoing ESS. The paper disclosed that if operation cavities didn't involve in middle turbinate, inferior turbinate and nasal septum, no packing method could be chosen; Otherwise, packing with different materials could be chosen, both methods could control the postoperative hemorrhage in a safe range. But in order to reducing patients' pain and operation cavities' reaction, it suggests operators had better choose no packing method or packing with absorbable hemostate gauze.
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Strelkov SV, Tao Y, Shneider MM, Mesyanzhinov VV, Rossmann MG. Structure of bacteriophage T4 fibritin M: a troublesome packing arrangement. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 1998; 54:805-16. [PMID: 9757094 DOI: 10.1107/s0907444997018878] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fibritin, a 52 kDa product of bacteriophage T4 gene wac, forms 530 A long fibers, named whiskers, that attach to the phage neck and perform a helper function during phage assembly. Fibritin is a homotrimer, with its predominant central domain consisting of 12 consecutive alpha-helical coiled-coil segments linked together by loops. The central domain is flanked by small globular domains at both ends. Fibritin M is a genetically engineered fragment of the wild type and contains 74 amino-acid residues corresponding to the last coiled-coil segment and the complete carboxy-terminal domain. The crystals of fibritin M belong to the rare space group P3 with three crystallographically independent trimers in the unit cell. The structure has been established at 1.85 A resolution by combining molecular and isomorphous replacement techniques. One of the two heavy-atom derivatives used was gaseous xenon. A substantial fraction of residues in each independent trimer is disordered to various extents in proportion to the lack of restraints on the molecules provided by the lattice contacts. Accurate modeling of the solvent present in the crystals was crucial for achieving good agreement with experimental data.
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Tao Y, Marzluf GA. Analysis of a distal cluster of binding elements and other unusual features of the promoter of the highly regulated nit-3 gene of Neurospora crassa. Biochemistry 1998; 37:11136-42. [PMID: 9693010 DOI: 10.1021/bi980224i] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In Neurospora crassa, the expression of the nit-3 gene (nitrate reductase) is dependent upon nitrogen derepression and nitrate induction and is regulated by two positive-acting transcription factors, NIT2 and NIT4, and a negative regulator, NMR. The presence of a tightly linked cluster of NIT2 and NIT4 binding sites suggested that their close spacing might be required for a synergistic interaction of the NIT2 and NIT4 proteins. We show here that the NIT2 and NIT4 binding sites can be separated without affecting either the expression level or the precise regulation of the nit-3 gene. Studies conducted on the NIT2 site II, which contains only a single GATA element and yet plays a major role in nit-3 gene expression, showed that nucleotides both 5' and 3' of the GATA sequence were important for strong DNA binding in vitro and its activation function in vivo. The nit-3 promoter contains two long AT-rich sequences, one of which is located just upstream of the transcription start sites and is required for optimal promoter function. The nit-3 transcript contains eight TACC repeats in its 5' noncoding region which appear to be involved in mRNA instability. Deletion of these TACC repeats led to a significant increase in the stability of nit-3 mRNA.
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Tao Y, Gao Q, Cui Y. [The valuation of paranasal sinus coronal CT scanning in endoscopy sinus surgery]. LIN CHUANG ER BI YAN HOU KE ZA ZHI = JOURNAL OF CLINICAL OTORHINOLARYNGOLOGY 1998; 12:346-8. [PMID: 11263154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
We applied coronal CT scanning of paranasal sinus to 260 patients with chronic sinusitis before they were performed endoscopy sinus surgery. The correct diagnostic rate was 99.2% in our study. The positive findings of CT were compared with that from normal person. By analyzing, we consider that coronal CT scanning can clearly reveal various anatomic variation for all sinuses, also, it is valuable in evaluating the difficulties of endoscopic sinus surgery and preventing dangerous operative complications.
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315
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Liu W, Tao Y, Siebenmorgen TJ, Chen H. Digital Image Analysis Method for Rapid Measurement of Rice Degree of Milling. Cereal Chem 1998. [DOI: 10.1094/cchem.1998.75.3.380] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Oelgeschläger T, Tao Y, Kang YK, Roeder RG. Transcription activation via enhanced preinitiation complex assembly in a human cell-free system lacking TAFIIs. Mol Cell 1998; 1:925-31. [PMID: 9660976 DOI: 10.1016/s1097-2765(00)80092-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In contrast to previous findings in cell-free systems reconstituted with partially purified metazoan factors, we demonstrate dramatic activation of transcription in a TBP-dependent but TAFII-independent manner in HeLa nuclear extracts immunodepleted of TBP and major TAFIIs. Single-round transcription assays reveal that TAFII-independent activation is manifested at the level of productive preinitiation complex formation and that TAFIIs actually impair functional preinitiation complex assembly in a core promoter-specific manner. Furthermore, TAFIIs appear to elevate absolute levels of transcription under multiple-round transcription conditions, presumably by facilitating secondary initiation events. Finally, human coactivator activities related to those in yeast RNA polymerase II/mediator complexes appear to function in unfractionated HeLa nuclear extracts.
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317
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Huang Q, Wang J, Tao Y. [The structure, function and mutation of Rb gene promoter in normal individuals and retinoblastoma patients]. ZHONGHUA ZHONG LIU ZA ZHI [CHINESE JOURNAL OF ONCOLOGY] 1998; 20:165-7. [PMID: 10920996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
OBJECTIVE To investigate the DNA sequence of the 5' untranslated region of the Rb gene in normal individuals and retinoblastoma patients and identify the elements involved in transcription regulation of Rb gene. METHODS SSCP analysis and direct genomic DNA sequencing were used to identify variations or alterations in DNA of normal adult WBC and tumor DNA of retinoblastoma patients. The different DNA fragments located in the 5' untranslated region of Rb gene were amplified and inserted into an expression plasmid with a CAT reporter gene. The capacity of transcription regulation of isolated DNA fragments was determined by CAT assay. RESULTS A 240 bp DNA fragment located between -327(-)-87 bp upstream of the first starting codon was shown to be the sequence with essential promoter function. The Sp1/RBF-1, ATF and E2F binding sites were present in this region and positive and negative elements were found further upstream and downstream. Four of 5 naturally occurring mutations were identified in either Sp1/RBF-1 or ATF binding sites from 302 patients with retinoblastoma. All these mutants had reduced CAT activity. However, 100 cases of normal adults did not show any variant DNA sequence in the same region. CONCLUSION The promoter DNA sequence of Rb gene is quite stable. Its variation usually leads to reduction in promoter activity which may be associated with genetic susceptibility to retinoblastoma.
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Purrello M, Di Pietro C, Viola A, Rapisarda A, Stevens S, Guermah M, Tao Y, Bonaiuto C, Arcidiacono A, Messina A, Sichel G, Grzeschik KH, Roeder R. Genomics and transcription analysis of human TFIID. Oncogene 1998; 16:1633-8. [PMID: 9569032 DOI: 10.1038/sj.onc.1201673] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
TFIID, a multisubunit protein comprised of TBP (TATA box-binding protein) and TAF(II)s (TBP-associated factors), has a central role in transcription initiation at class II promoters. TAF(II)s role as mediators of regulatory transcription factors, such as pRb and p53, and their involvement in signal transduction pathways suggest that some may participate in the control of cell proliferation and differentiation: therefore, they could be considered potential protooncogenes or antioncogenes. With the aim of starting to analyse these potential roles, we have determined the genomic position of nine human TAF(II) genes (TAF[II]250, TAF[II]135, TAF[II]100, TAF[II]80, TAF[II]55, TAF[II]43, TAF[II]31, TAF[II]28, TAF[II]20/15) and of two previously unknown sequences related to TAF(II)250 and TAF(II)31, respectively. Except for those encoding TAF(II)250 and TAF(II)31, these genes are present in a single copy and, with the exclusion of those for TAF(II)43 and TAF(II)28 (both at 6p21), are localized in different segments of the genome. Indeed, six of them map to a chromosomal region commonly altered in specific neoplasias, which defines them as candidates for involvement in oncogenesis. Our experiments also demonstrate that TAF(II) transcripts are synthesized ubiquitously, mostly at low levels similar to those of TBP. Interestingly, the amount of the major mRNA species detected by TAF(II)20/15 cDNA is higher, which suggests that the polypeptide it encodes may also perform functions independently of TFIID. TAF(II) isoforms, indicated by additional bands on Northern blots, may play a role in modulation of TFIID function. These data will be useful for analysing variations of TAF(II) mRNA phenotype during cell proliferation, differentiation and development, both normal and pathological.
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Xiao H, Tao Y, Greenblatt J, Roeder RG. A cofactor, TIP30, specifically enhances HIV-1 Tat-activated transcription. Proc Natl Acad Sci U S A 1998; 95:2146-51. [PMID: 9482853 PMCID: PMC19278 DOI: 10.1073/pnas.95.5.2146] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Replication of HIV-1 requires the viral Tat protein, which increases the extent of transcription elongation by RNA polymerase II after activation at the single viral long terminal repeat (LTR) promoter. This effect of Tat on transcription requires Tat interactions with a 5' region (TAR) in nascent transcripts as well as Tat-specific cofactors. The present study identifies a cellular protein, TIP30, that interacts with Tat and with an SRB-containing RNA polymerase II complex both in vivo and in vitro. Coexpression of TIP30 specifically enhances transactivation by Tat in transfected cells, and immunodepletion of TIP30 from nuclear extracts abolishes Tat-activated transcription without affecting Tat-independent transcription. These results implicate TIP30 as a specific coactivator that may enhance formation of a Tat-RNA polymerase II holoenzyme complex.
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Brown KE, Kinter MT, Oberley TD, Freeman ML, Frierson HF, Ridnour LA, Tao Y, Oberley LW, Spitz DR. Enhanced gamma-glutamyl transpeptidase expression and selective loss of CuZn superoxide dismutase in hepatic iron overload. Free Radic Biol Med 1998; 24:545-55. [PMID: 9559866 DOI: 10.1016/s0891-5849(97)00284-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Liver injury caused by iron overload is presumed to involve lipid peroxidation and the formation of products such as 4-hydroxynonenal (4HNE), which has been implicated in hepatic fibrogenesis. Cellular antioxidants that modulate the formation and detoxification of compounds such as 4HNE may represent important protective mechanisms involved in the response to iron overload. This study examines the relationship between 4HNE, collagen content, and antioxidant defenses in the livers of rats fed carbonyl iron for 10 weeks. Iron-loading resulted in significant increases in iron (8.8-fold), 4HNE (1.7-fold), and hydroxyproline (1.5-fold). Total glutathione content was unchanged by iron, but gamma-glutamyl transpeptidase activity (GGT) increased sixfold and CuZn superoxide dismutase (CuZnSOD) activity decreased >9%. GGT colocalized with iron deposition and was associated with increased GGT mRNA. Decreased CuZnSOD activity was paralleled by a reduction in CuZnSOD protein on Western blot and immunohistochemistry, but no decrease in CuZnSOD mRNA. Glutathione S-transferase (GST) and Mn superoxide dismutase (MnSOD) activities were also significantly increased by iron loading. These results demonstrate that iron overload significantly alters the expression of antioxidant enzymes associated with glutathione (GGT and GST) and superoxide metabolism (CuZnSOD and MnSOD). Furthermore, the localized induction of GGT may enhance detoxification of lipid peroxidation-derived aldehydes via glutathione-dependent pathways in iron-loaded hepatocytes. These alterations in antioxidant defenses may represent an adaptive response, limiting accumulation 4HNE, and thus, stimulation of collagen synthesis, accounting for the mild fibrogenic response seen in this model of iron overload.
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Tao Y, Marzluf GA. Synthesis and differential turnover of the CYS3 regulatory protein of Neurospora crassa are subject to sulfur control. J Bacteriol 1998; 180:478-82. [PMID: 9457847 PMCID: PMC106911 DOI: 10.1128/jb.180.3.478-482.1998] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/1997] [Accepted: 11/18/1997] [Indexed: 02/06/2023] Open
Abstract
The transcription factor CYS3 of Neurospora crassa is a positive regulator of the sulfur regulatory circuit which contains many structural genes involved in sulfur metabolism. Expression and degradation of the CYS3 protein are precisely regulated in a sulfur-dependent manner. cys-3 expression was found to be fully repressed by high concentrations of methionine or inorganic sulfate present in the culture medium and to be derepressed when these favored sulfur sources were limited. cys-3 transcripts could be readily detected within 2 h after derepression, whereas the CYS3 protein was not found until after 4 h. CYS3 is stable, with a half-life greater than 4 h under low-sulfur conditions when it is required for cell growth. However, it is degraded relatively quickly when methionine or inorganic sulfate becomes available. Upon sulfur repression, cys-3 transcripts disappeared within 30 min with an estimated half-life of 5 min whereas CYS3 protein almost entirely disappeared in 1 h with a half-life of approximately 10 min. These results suggest that a selective elimination of CYS3 is a highly regulated process. Site-directed mutagenesis showed that Lys-105 of CYS3 is important for its instability. The change of this single residue from lysine to glutamine resulted in a prolonged half life of CYS3 and impaired responsiveness of CYS3 degradation to sulfur level changes.
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Tao Y, Kassatly RF, Cress WD, Horowitz JM. Subunit composition determines E2F DNA-binding site specificity. Mol Cell Biol 1997; 17:6994-7007. [PMID: 9372931 PMCID: PMC232556 DOI: 10.1128/mcb.17.12.6994] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The product of the retinoblastoma (Rb) susceptibility gene, Rb-1, regulates the activity of a wide variety of transcription factors, such as E2F, in a cell cycle-dependent fashion. E2F is a heterodimeric transcription factor composed of two subunits each encoded by one of two related gene families, denoted E2F and DP. Five E2F genes, E2F-1 through E2F-5, and two DP genes, DP-1 and DP-2, have been isolated from mammals, and heterodimeric complexes of these proteins are expressed in most, if not all, vertebrate cells. It is not yet clear whether E2F/DP complexes regulate overlapping and/or specific cellular genes. Moreover, little is known about whether Rb regulates all or a subset of E2F-dependent genes. Using recombinant E2F, DP, and Rb proteins prepared in baculovirus-infected cells and a repetitive immunoprecipitation-PCR procedure (CASTing), we have identified consensus DNA-binding sites for E2F-1/DP-1, E2F-1/DP-2, E2F-4/DP-1, and E2F-4/DP-2 complexes as well as an Rb/E2F-1/DP-1 trimeric complex. Our data indicate that (i) E2F, DP, and Rb proteins each influence the selection of E2F-binding sites; (ii) E2F sites differ with respect to their intrinsic DNA-bending properties; (iii) E2F/DP complexes induce distinct degrees of DNA bending; and (iv) complex-specific E2F sites selected in vitro function distinctly as regulators of cell cycle-dependent transcription in vivo. These data indicate that the specific sequence of an E2F site may determine its role in transcriptional regulation and suggest that Rb/E2F complexes may regulate subsets of E2F-dependent cellular genes.
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Bazan HE, Tao Y, DeCoster MA, Bazan NG. Platelet-activating factor induces cyclooxygenase-2 gene expression in corneal epithelium. Requirement of calcium in the signal transduction pathway. Invest Ophthalmol Vis Sci 1997; 38:2492-501. [PMID: 9375567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
PURPOSE To investigate the effect of the inflammatory mediator platelet-activating factor (PAF) in the induction of the inducible prostaglandin H synthase-cyclooxygenase-2 (COX-2) gene expression in corneal epithelium. METHODS Rabbit corneas were incubated in organ culture with or without carbamyl PAF (cPAF, 100 nM). The effects of PAF antagonist BN50730 (10 microM), protein synthesis inhibitor cycloheximide (CHX; 30 micrograms/ml), RNA synthesis inhibitor actinomycin D (50 micrograms/ml), and tumor promoter phorbol ester (TPA); (100 nM) were tested. Total RNA for corneal epithelium was analyzed by Northern blot analysis using mouse COX-2 cDNA fragments labeled with 32P as probes. Western blots were performed using mouse monoclonal antibodies. Primary cultures of rabbit corneal epithelium were loaded with the fluorescent dye fluo-3 AM and changes in intracellular calcium concentration [Ca2+]i were analyzed by laser scanning confocal microscopy. RESULTS Platelet-activating factor induction of COX-2 expression was detectable by Northern blot analysis at 2 hours, peaked at 4 hours, and remained increased for as long as 8 hours. At 16 hours, there was a marked increase in COX-2 expression. The effect was abolished by the PAF antagonist. TPA also induced COX-2 gene expression. Neither PAF-nor TPA-induced expression was inhibited by CHX. In a Ca(2+)-free medium, there was a 50% inhibition of COX-2 gene induction by PAF. The calcium ionophore A23187 also caused an increase in expression of COX-2 messenger RNA; this did not occur in Ca(2+)-free medium. Confocal microscopy imaging showed that after the addition of PAF, there was a transient increase in [Ca2+]i in corneal epithelial cells that peaked between 30 and 60 seconds. The increase was inhibited in the presence of BN50730 or in a Ca(2+)-free medium. A23187 also caused a transient increase in [Ca2+]i that was not altered in cells previously treated with PAF or BN50730. CONCLUSIONS PAF may enhance prostaglandin synthesis in the corneal epithelium by increasing COX-2 gene expression. This increase is by means of transcriptional activation of the gene and results in increased COX-2 protein formation. Influx of Ca2+ due to PAF stimulation is required to induce the COX-2 gene. A PAF antagonist abolishes all PAF effects and could be of therapeutic value by modulating ocular inflammation at the level of COX-2 gene expression.
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Tao Y, Black IB, DiCicco-Bloom E. In vivo neurogenesis is inhibited by neutralizing antibodies to basic fibroblast growth factor. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/(sici)1097-4695(199709)33:3<289::aid-neu7>3.0.co;2-y] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Tao Y, Black IB, DiCicco-Bloom E. In vivo neurogenesis is inhibited by neutralizing antibodies to basic fibroblast growth factor. JOURNAL OF NEUROBIOLOGY 1997; 33:289-96. [PMID: 9298766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
While extracellular growth factors govern neuronal precursor mitosis in culture, little is known about their roles in regulating neurogenesis in vivo. Previously, we reported that subcutaneously administered basic fibroblast growth factor (bFGF) promoted neuroblast proliferation in P1 rat brain, in regions in which bFGF and FGF receptors are expressed during development. To define the role of endogenous bFGF in neurogenesis, we employed a neutralizing monoclonal antibody to the factor. In culture, bFGF-induced granule precursor proliferation was progressively inhibited by increasing concentrations of antibody. In contrast, heat-inactivated or nonneutralizing anti-bFGF antibodies were ineffective. The inhibition was specific for bFGF, since EGF-induced [3H]dT incorporation was not altered. To study effects in vivo, neutralizing antibody was administered to newborn rats via the cisterna magnum. Four hours after injection, DNA synthesis in cerebellum and hippocampus was decreased by 53% and 63%, respectively, suggesting that endogenous bFGF was involved in brain development. To define effects on neurogenesis specifically, granule cell precursors were isolated after antibody treatment. [3H]dT incorporation in granule precursors was decreased by 50%, indicating that the neutralizing antibody inhibited neuroblast proliferation in vivo. In contrast, no reduction was observed using nonneutralizing or the heat-inactivated antibodies. The inhibition of precursor proliferation following immunoneutralization of bFGF in vivo suggests that the endogenous factor normally regulates brain neurogenesis.
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