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Y F Hu

Publications and source records attributed to Y F Hu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Characterization of a novel trans-activation domain of BRCA1 that functions in concert with the BRCA1 C-terminal (BRCT) domain.

Mutations in the breast cancer susceptibility gene, BRCA1, account for a significant proportion of hereditary breast and ovarian cancers. The BRCA1 C-terminal (BRCT) domain, which can activate transcription when fused to a heterologous DNA binding domain, is required for BRCA1 function in suppression of tumorigenesis. Here, we provide evidence for a new activation domain in BRCA1 that lies adjacent to the BRCT domain. We name the two domains AD1 and AD2, respectively. Like AD2, the newly discovered AD1 can act independently as an activation domain in both yeast and human cells. However, unlike AD2, AD1 activity in mammalian cells is cell type context-dependent. Furthermore, combination of these two domains in mammalian cells can result in a robust synergy in transcriptional activation. A highly conserved coiled-coil motif in AD1 is required for the cooperative transcription activation. Interestingly, the functional cooperativity between AD1 and AD2 is absent in certain breast and ovarian cancer cell lines, although each domain can still activate transcription. Therefore, the differential and cooperative actions of the two activation modules may contribute to the heterogeneous risk of BRCA1 mutations in different tissues.

Amino Acid Sequence↗
PubMed2000

A functional comparison of BRCA1 C-terminal domains in transcription activation and chromatin remodeling.

The BRCA1 C-terminal (BRCT) domain is present in a number of proteins that are involved in various aspects of chromosomal events. The BRCT domain of BRCA1 is important for its function in DNA repair and transcriptional activation. When tethered to chromosomal DNA, this region of BRCA1 is capable of inducing changes in chromatin structure. Despite the sequence homology and functional proximity shared by the BRCT-containing proteins, it is not clear whether different BRCT domains confer a common biochemical activity. Much less is known about the functional significance of the characteristic amino acid residues in the BRCT motif. Here, we show that chromatin remodeling and transcription activation is not a common feature of BRCT domains. However, the BRCT domain of the multi-functional repressor-activator protein 1 (RAP1) can activate transcription and remodel chromatin in a manner similar to that shown for the BRCA1 BRCT domain. Most of the conserved amino acid residues in the second BRCA1 BRCT domain are essential for its function in transcriptional activation. In contrast, mutations of many analogous amino acid residues in the RAP1 BRCT domain greatly elevate the transcriptional activity. These data indicate that the conserved residues in these two BRCT domains may play different roles in transcriptional activation.

Amino Acid Sequence↗
PubMed2000

First results from the Canadian SGM beamline at SRC.

The first experimental results obtained from the Canadian SGM beamline at SRC (Synchrotron Radiation Centre, University of Wisconsin-Madison, USA) are reported. The beamline is based on the Dragon-type design, with a constant deviation angle, using photons from a second-generation bending-magnet light source. The medium-energy grating on this beamline covers a photon energy range from 240 to 700 eV, with a ruling density of 600 lines mm(-1). A maximum resolving power of approximately 10000 is achieved at a photon energy of approximately 400 eV. Gas-phase absorption spectra collected at the N, O and C K-edges are presented to demonstrate the excellent performance of this beamline. High-resolution absorption spectra of some C- and Ti-containing solid-state samples are also reported.

Journal Article↗
PubMed2000

Variable-energy photoelectron spectroscopy of substituted rhenium and manganese pentacarbonyls: molecular orbital assignments and the interatomic resonant effect.

High-resolution variable-energy photoelectron spectra of M(CO)5X [M = Re, X = Re(CO)5, Cl, Br, and I; and M = Mn, X = Mn(CO)5 and Br] are reported. Tunable synchrotron radiation is used to distinguish the Re 5d and Br 4p orbital based peaks for the controversial Re(CO)5Br. Our results provide firm molecular orbital assignments for all of these molecules. The valence orbital in the ordering of ionization energies for M(CO)5Cl (M = Mn and Re) and Mn(CO)5Br is a 1(M-X) > e(X) > b2(M) > e(M); but for M(CO)5I (M = Mn and Re) and Re(CO)5Br the ordering is a1(M-X) > e(M) > b2(M) > e(X). The crossover of the HOMO in the Re molecules due to the change in the halogen electronegativities occurs at Re(CO)5Br. The metal np-->nd resonance is observed for all of these molecules. For molecules like M2(CO)10 (M = Re and Mn) and Mn(CO)5Br, the observation of this np-->nd resonance is useful in assigning the metal nd based orbitals in their valence level spectra. However, for molecules like Re(CO)5X (X = Br and Cl), a np-->nd type resonance is observed on bands arising from both Re 5d and halogen mp based orbitals. This new resonant effect on the ligand-based orbitals is shown to be mainly due to the interatomic resonant effect. The core and valence level chemical shifts of these compounds are treated using Jolly's approach to confirm the assignments for the valence level spectra of some of these molecules. The high-resolution inner valence and core level spectra of these compounds are reported. Broadening of Re 4f, Br 3d, and I 4d core level spectra is discussed. The Auger peaks are observed in the high-resolution, high-intensity Br 3d of Re(CO)5Br and I 4d of Re(CO)5I spectra.

Journal Article↗
PubMed2000

Photoinduced dehydrogenation of defects in undoped a-si:H using positron annihilation spectroscopy.

We report changes in variable-energy positron annihilation spectroscopy measurements on undoped hydrogenated amorphous silicon films after light soaking. The change, seen predominantly in the high momentum band of the annihilation radiation, is not reversed by thermal annealing. We suggest, following recent models of the Staebler-Wronski effect, that light exposure induces hydrogen trapped in vacancylike defects to become mobile in the Si network. The observations place constraints on models of hydrogen motion fitting macroscopic Staebler-Wronski effect kinetics and may help to achieve a definitive description of metastability in a-Si:H.

Journal Article↗
PubMed2000

Developmental, cellular, and molecular basis of human breast cancer.

Breast cancer, which is the most common neoplastic disease in females and accounts for up to one third of all new cases of women's cancer in North America, continues to rise in incidence. In addition, the mortality caused by this disease has remained almost unchanged for the past 5 decades, becoming only second to lung cancer as a cause of cancer-related death. The failure in eradicating this disease is largely due to the lack of identification of a specific etiologic agent, the precise time of initiation, and the molecular mechanisms responsible for cancer initiation and progression. Despite the numerous uncertainties surrounding the origin of cancer, there is substantial evidence that breast cancer risk relates to endocrinologic and reproductive factors. The development of breast cancer strongly depends on the ovary and on endocrine conditions modulated by ovarian function, such as early menarche, late menopause, and parity. However, the specific hormone or hormone combinations responsible for cancer initiation have not been identified, and their role as protective or risk factors is still incompletely understood. A highly significant female hormone is estrogen, which is involved in the development of a variety of cancers, but it is still unclear whether estrogens are carcinogenic to the human breast. An understanding of whether estrogens cause mutations, and, if so, whether they act through hormonal effects activated by receptor binding, cytochrome P450-mediated metabolic activation, or compromise the DNA repair system, is essential for determining whether this steroid hormone is involved in the initiation or progression of breast cancer. This knowledge has to be based on a multidisciplinary approach encompassing studies of the development of the breast, influence of hormones on the differentiation of individual structures, and their interrelations in the pathogenesis of breast cancer. The analysis of the mechanisms involved would require confirmation in the adequate in vitro models and determination of the role played by genomic alterations in both cancer initiation and progression.

Breast↗
PubMed2000

S100P calcium-binding protein overexpression is associated with immortalization of human breast epithelial cells in vitro and early stages of breast cancer development in vivo.

The mechanism of cell immortalization of human breast epithelial cells leading to neoplastic transformation is not clear. The isolation and characterization of a spontaneously immortalized human breast epithelial cell line, MCF-10F, have provided a valuable tool to identify genes involved in this process. Using the technique of differential display, we have identified seven cDNA bands differentially displayed in the MCF-10F cells when compared with the mortal S130 cells from which MCF-10F was originated. One of these bands was isolated and cloned. Sequence analysis revealed 99% homology to the EF-hand calcium-binding protein S100P (Placental). The clone was overexpressed in the immortal cell line MCF-10F when compared to the mortal counterpart S130 or other primary cultures of human breast epithelial cells. In addition, it was highly expressed in chemically transformed breast epithelial cell lines (BP1E and D3. 1), breast cancer cell line T47D, as well as in three invasive ductal carcinomas when compared to their normal adjacent tissue. The S100P protein was localized by immunohistochemistry, using a monoclonal antibody against the same amino acid sequence of the gene cloned, in ductal hyperplasias, in situ and invasive ductal carcinoma, but not in the normal tissues. We concluded that S100P overexpression is an early event that might play an important role in the immortalization of human breast epithelial cells in vitro and tumor progression in vivo.

Base Sequence↗
PubMed1999

Chromatin remodeling and activation of chromosomal DNA replication by an acidic transcriptional activation domain from BRCA1.

An increasing number of transcription factors have been shown to activate DNA replication. However, the underlying mechanism remains to be elucidated. Here it is shown that when tethered to a cellular replication origin, the acidic transcriptional activation domain of the breast cancer protein BRCA1 alters the local chromatin structure and stimulates chromosomal DNA replication. Cancer-predisposing mutations in BRCA1 that abolish transcriptional activation also prevent chromatin remodeling and activation of replication. Chromatin remodeling occurs even in the absence of a functional replication origin. Thus, increasing chromatin accessibility may be an important mechanism used by transcription factors to facilitate multiple nuclear processes.

BRCA1 Protein↗
PubMed1999

Functional roles of chromosomes 11 and 17 in the transformation of human breast epithelial cells in vitro.

Genomic alterations in primary breast cancer play a role in the initiation and progression of the disease. We have analyzed the molecular events involved in the initiation and progression of the neoplastic process in an in vitro experimental system. Immortalization of human breast epithelial cells (HBEC) is associated with 3:9 translocation, p53 mutation and microsatellite instability (MSI) of chromosomes 11p13, and 17p. BP1-E cells, derived from the immortalized MCF-10F cells transformed by the carcinogen benzo(a)pyrene (BP), express in vitro growth advantage, anchorage independence, enhanced chemoinvasiveness, loss of ductulogenic capabilities and tumorigenesis in a heterologous host. This neoplastic progression is also associated with mutations and/or amplification of c-H-ras, int-2, c-neu, c-myc and MDM2, MSI at 11q25 and 13q12-q13 and loss of heterozygosity at 17p. In order to test whether chromosomes 11 or 17 play a functional role in the phenotypic expression of transformation of BP1E cells, we utilized microcell-mediated chromosome transfer (MMCT) technique for inserting the corresponding normal chromosomes to these transformed cells. BP1E cells were transfected with PsV2neo plasmid and fused with microcells obtained from the mouse cell line A9, containing a normal chromosome 11 or 17 (A9-11neo and A9-17neo cells, selected in G418 and cloned. Sixteen primary microcell hybrids from each chromosome transfer, designated BP1E-11neo and BP1E-17neo survived selection in G-418 containing medium. A single clone from each group, BP1E-11neo #145 and BP1E-17neo D100, survived subcloning and were utilized for a detailed panel of analyses. The presence of a donor chromosome was confirmed by dual color fluorescence in situ hybridization (FISH), southern blot analysis of the marker vector pSV2neo, and microsatellite polymorphism analysis. The transfer of the normal chromosomes 11 and 17 resulted in a 50% and 90% inhibition of cell growth respectively, and reduced both colony efficiency and colony size. Telomerase activity was significantly reduced only by chromosome 17 insertion, providing a possible explanation for the more significant senescence observed in BP1E-17neo D100 cells. Microsatellite polymorphism analysis revealed that three loci, 11q13-23, 11q23.1, and 11q23.3 (markers D11S911, DRD2, and D11S29) were retained in BP1E-11neo #145 cells, and two, 17q24.2-25.2, 17q25.2 (markers D17S515 and D17S785 were retained in BP1E-17neo D100 cells. We conclude that the specific regions of normal chromosomes 11 and 17 transferred play a functional role in the expression of immortal and transformed phenotypes of HBEC in vitro.

Blotting, Southern↗
PubMed1998

Biological and molecular basis of human breast cancer.

Human breast cancer remains the most common malignancy in the American women. The ultimate cure of this disease relies on a better understanding of the mechanisms underlying the initiation and progression of this disease. The neoplastic transformation of HBEC in vitro represents a successful model for obtaining knowledge on the molecular and biological alterations that may contribute to the tumorigenic mechanisms. We have presented here a current understanding of chemically transformed HBEC in the following aspects: 1. Factors affecting the transformation of HBEC such as genetic predisposition and differentiation status and prior immortalization; 2. New targets for studying the mechanism of cell immortalization such as alterations in telomerase activity and differential expression of cell cycle dependent genes as well as others recently isolated through differential cloning such as H-ferritin, and a calcium binding protein; 3. Epigenetic and genetic mechanisms underlying cell transformation; 4. The association of microsatellite instability in specific loci on chromosomes 11, 13, and 16 with the progression of cell transformation; and 5. The application of microcell mediated chromosome transfer technique as an approach to testing the functional role of specific genes whose dysregulation or loss of function may contribute to the ultimate cell transformation. Further efforts in this cell system will be directed to determine the roles of identified molecular changes as well as the mapping/cloning of tumor suppressor or senescence genes such as those that may reside on chromosomes 11 or 17.

Breast Neoplasms↗
PubMed1998

Increased expression of estrogen receptor beta in chemically transformed human breast epithelial cells.

Recent molecular cloning of estrogen receptor beta (ERbeta) suggests alternative pathways of estrogen signaling, but little is known concerning the role of ERbeta in the development of human breast cancer. In the present study, expression of ERalpha and ERbeta mRNA was determined in a series of chemically transformed human breast epithelial cells as well as various normal and malignant breast cancer cell lines. We observed a very low level of ERbeta expression in the mortal S130 and the spontaneously immortalized MCF10-F human breast epithelial cell lines. As MCF-10F cells were treated with environmental chemical carcinogens, an elevated level of ERbeta expression was observed in the resultant transformed BP1, D3 and BP1-ras cells. An even higher level of ERbeta expression was detected in the more transformed BP1-E, D3-1 and D3-1-ras cell lines. Therefore, results from our study indicate that expression of ERbeta can be induced in chemical carcinogen-transformed human breast epithelial cells, and the more transformed cells showed higher levels of ERbeta expression, regardless of which chemical carcinogens were initially used for cell transformation. These results suggest that expression of ERbeta may contribute to the initiation and progression of chemical carcinogen-induced neoplastic transformation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

[Role of PHO85 gene in the cell cycle control of budding yeast].

By homo-recombination with yeast intergrating plasmids, a serial of haploid mutants of budding yeast YPH499 had been constructed, which included pho85 delta strain YPH600, pho85 delta cln1 delta strain YPH610, cln1 delta cln2 delta strain YPH640 and galactose inducible strain YPH630 (pho85 delta cln1 delta cln2 delta (GAL1-10PHO85)). By analyzing the growth rate of different strains, we concluded that PHO85 gene have greater influence than CLN1 and CLN2 genes on cell growth control. After transferred from galactose media to glucose media, the tri-mutant cells collected at intervals were observed with microscope and analyzed by FACS. The results showed that the tri-mutant cells arrest in G1 phase when they were transferred to glucose media.

Cell Cycle↗
PubMed1994

Presence of antitumor activities in the milk collected from gossypol-treated dairy cows.

Two human breast carcinoma cell lines (MCF-7, MCF-7 Adr) and a rat esophageal cancer cell line (RE-B2T) were used to evaluate the antiproliferative potential of gossypol (GP)-containing milk (GP-Milk), which was collected from Brown Swiss dairy cows treated daily with federally allowable 450 ppm of GP for 6 days. Treatment of the cultured cancer cells with GP-Milk for 24 h significantly inhibited the rates of 3H-thymidine incorporation during the ensuing 3-h period in all three tumorigenic cell lines. The inhibitory effects of GP-Milk occurred in a dose-dependent manner in all cases, but the calculated ED50 varied with cell lines. ED50 for GP-Milk was estimated at 10% for wild-type MCF-7 human breast cancer cells, 15% for multidrug-resistant MCF-7 Adr human breast cancer cells and 50% for RE-B2T rat esophageal carcinoma cells. The potential of GP-Milk as a dietary supplement for the prevention and/or treatment of human breast cancer is discussed in this paper.

Animals↗
PubMed1994

Detection of keratinocyte growth factor (KGF) transcripts from normal human and archival canine benign prostatic hyperplastic tissues.

This study examined the expression of keratinocyte growth factor (KGF) gene in human and canine prostatic tissues. KGF transcript was detected in normal human prostatic tissues by reverse transcription and polymerase chain reactions (RT-PCR). PCR-generated human KGF complementary DNA (cDNA) clone was confirmed by restriction enzyme digestion analysis and partial DNA sequencing. Expression of KGF in archival canine benign prostatic hyperplastic tissues was also examined. In a pilot experiment, RNAs isolated from formalin-fixed (FF) and formalin-fixed and paraffin-embedded (FFPE) canine prostatic tissues were shown to be of sufficient quality to permit amplification of KGF mRNA by RT-PCR. The transcript of a housekeeping gene, glucose-6-phosphate dehydrogenase (G6PD), was detected by RT-PCR indicating the quality of RNAs to be more than adequate for RNA expression analysis. Later, total RNA from two archival canine FF prostate tissue types, benign prostatic hyperplasis and mild glandular hyperplasia, were used to amplify canine KGF transcripts. Southern hybridization analysis using rat and human KGF cDNAs as probes confirmed the fidelity of the amplified PCR product and it was indeed canine KGF.

Animals↗
PubMed1994

[Gliomatosis peritonei].

Gliomatosis peritonei (GP) is the implantation of glial tissue on the peritoneal surface in patients with solid ovarian teratoma. The average age at time of biopsy was 17.4 years in this study. The largest ovarian teratoma was 30cm in diameter with an average of 21.4cm. The tumor capsules were ruptured and adhered to the omentum in 5 cases. Peritoneal dissemination was detected in one patient at the second operation 10 months after the first one. It's believed that injury to the tumor capsule may have a role in peritoneal implantation. In general, regardless of the grade of the primary ovarian teratoma, the implanted peritoneal nodules consisted exclusively of GFAP and S-100 protein positive mature astroglia. The average length of follow up was 36.2 months. One patient with GP is alive and clinically healthy 8 years and 3 months post-operatively. The authors consider GP is a benign condition and associated with an improved prognosis for solid ovarian teratoma.

Adolescent↗
PubMed1993

Gossypol inhibits basal and estrogen-stimulated DNA synthesis in human breast carcinoma cells.

Estrogen stimulates the growth of hormone-dependent human breast cancer. Failure of chemotherapy frequently results from the development of multidrug resistance. Gossypol (GP), a naturally occurring toxin, inhibits the growth of various carcinoma cells. Thus, the effects of GP on 17 beta-estradiol (E2)-stimulated DNA synthesis were studied in two hormone-dependent human breast carcinoma cell lines: the wild-type MCF-7 and the multidrug-resistant MCF-7 Adr cells. Cells (5 x 104/well) were cultured for 24 hrs in a chemically-defined, serum-free medium consisting of 1:1 mixture of Dulbecco's Modified Eagle's medium and Ham's nutrient mixture F12 (DMEM/F12) supplemented with insulin (5.0 micrograms/ml), transferrin (5.0 micrograms/ml), epidermal growth factor (EGF; 10.0 ng/ml) and antibiotics E2 (0 or 10.0 nM), GP (0, 2.5, 5.0, 10.0 or 20.0 microM) and bovine serum albumin (BSA; 0 or 0.1 mg/ml) were used as treatments in a factorial experimental design. Cells were treated for 24 hrs and finally pulsed with 3H-thymidine (5.0 microCi/ml) for 3 hrs. E2 significantly stimulated 3H-thymidine incorporation in both MCF-7 and MCF-7 Adr cells. GP at 10.0 and 20.0 microM inhibited both basal and E2-stimulated DNA synthesis in human breast cancer cells. The inhibitory effects of GP at 10.0 microM, but not at 20.0 microM, were blocked by BSA treatment. Results from the present study indicate that GP treatment was antiproliferative in both drug-sensitive and multidrug-resistant cancer cells and that the antiproliferative effects of GP on human breast cancer cells were mediated through mechanisms independent of estrogenic responses. Thus, GP could be potentially very useful for treatment of human breast cancer patients, especially those who have developed multidrug resistance.

Breast Neoplasms↗