Biomedical subjects

Bin Yu

Publications and source records attributed to Bin Yu.

64 records · Page 4Linked to original sources

PubMed2002

Regulation of aromatase promoter activity in human breast tissue by nuclear receptors.

Using the yeast one-hybrid approach to screen a human breast tissue hybrid cDNA expression library, we have found that four orphan/nuclear receptors, ERRalpha-1, EAR-2, COUP-TFI (EAR-3), and RARgamma, bind to the silencer (S1) region of the human aromatase gene. S1 down regulates promoters I.3 and II of the human aromatase gene. In this study, the interaction of EAR-2, COUP-TFI, and RARgamma with S1 was confirmed by DNA mobility shift analysis. In contrast to the findings that ERRalpha-1 behaves as a positive regulatory factor, these three nuclear receptors were found, by mammalian cell transfection experiments, to act as negative regulatory factors by binding to S1. Furthermore, the negative action of these three nuclear receptors could override the positive effect of ERRalpha-1. RT-PCR analysis of 11 cell lines and 55 human breast tumor specimens has shown that these nuclear receptors are expressed in human breast tissue. Since EAR-2, COUP-TFI, and RARgamma are expressed at high levels, it is likely that S1 is a negative regulatory element that suppresses aromatase promoters I.3 and II in normal breast tissue. In cancer tissue, S1 may function as a positive element since ERRalpha-1 is expressed, but EAR-2 and RARgamma are only present in a small number of tumor specimens. This hypothesis is sustained by the finding that there is a weak inverse correlation between the expression of COUP-TFI and that of aromatase in breast tumor tissue. Our studies have revealed that estrogen receptor alpha (ERalpha) can also bind to S1, in a ligand-dependent manner. By binding to S1, ERalpha down-regulates the aromatase promoter activity. These results demonstrate that nuclear receptors play important roles in modulating aromatase expression in human breast tissue.

Aromatase↗

PubMed2002

Arabidopsis disrupted in SQD2 encoding sulfolipid synthase is impaired in phosphate-limited growth.

The sulfolipid sulfoquinovosyldiacylglycerol is one of the three nonphosphorous glycolipids that provide the bulk of the structural lipids in photosynthetic membranes of seed plants. Unlike the galactolipids, sulfolipid is anionic at physiological pH because of its 6-deoxy-6-sulfonate-glucose (sulfoquinovose) head group. The biosynthesis of this lipid proceeds in two steps: first, the assembly of UDP-sulfoquinovose from UDP-glucose and sulfite, and second, the transfer of the sulfoquinovose moiety from UDP-sulfoquinovose to diacylglycerol. The first reaction is catalyzed by the SQD1 protein in Arabidopsis. Here we describe the identification of the SQD2 gene of Arabidopsis. We propose that this gene encodes the sulfoquinovosyltransferase catalyzing the second step of sulfolipid biosynthesis. Expression of SQD1 and SQD2 in Escherichia coli reconstituted plant sulfolipid biosynthesis in this bacterium. Insertion of a transfer DNA into this gene in Arabidopsis led to complete lack of sulfolipid in the respective sqd2 mutant. This mutant showed reduced growth under phosphate-limited growth conditions. The results support the hypothesis that sulfolipid can function as a substitute of anionic phospholipids under phosphate-limited growth conditions. Along with phosphatidylglycerol, sulfolipid contributes to maintaining a negatively charged lipid-water interface, which presumably is required for proper function of photosynthetic membranes.

Arabidopsis↗

PubMed2002

Identification of a substrate recognition site on Ubc9.

Human Ubc9 is homologous to ubiquitin-conjugating enzymes. However, instead of conjugating ubiquitin, it conjugates a ubiquitin homologue, small ubiquitin-like modifier 1 (SUMO-1), also known as UBL1, GMP1, SMTP3, PIC1, and sentrin. The SUMO-1 conjugation pathway is very similar to that of ubiquitin with regard to the primary sequences of the ubiquitin-activating enzymes (E1), the three-dimensional structures of the ubiquitin-conjugating enzymes (E2), and the chemistry of the overall conjugation pathway. The interaction of substrates with Ubc9 has been studied using NMR spectroscopy. Peptides with sequences that correspond to those of the SUMO-1 conjugation sites from p53 and c-Jun both bind to a surface adjacent to the active site Cys93 of human Ubc9, which has been previously shown to include residues that demonstrate the most significant dynamics on the microsecond to millisecond time scale. Mutations in this region, Q126A, Q130A, A131D, E132A, Y134A, and T135A, were constructed to evaluate the role of these residues in SUMO-1 conjugation. These alterations have significant effects on the conjugation of SUMO-1 with the target proteins p53, E1B, and promyelocytic leukemia protein and define a substrate binding site on Ubc9. Furthermore, the SUMO-1 conjugation site of p53 does not form any defined secondary structure when either free or bound to Ubc9. This suggests that a defined secondary structure at SUMO-1 conjugation sites in target proteins is not necessary for recognition and conjugation by the SUMO-1 pathway.

Binding Sites↗

PubMed2002

Differential regulation of thymus- and activation-regulated chemokine induced by IL-4, IL-13, TNF-alpha and IFN-gamma in human keratinocyte and fibroblast.

The CC chemokine thymus- and activation-regulated chemokine (TARC/CCL17) acts on CC chemokine receptor 4 (CCR4), which is known to be selectively expressed in Th2 cells. In order to compare the regulatory profiles of TARC production by tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, interleukin-4 (IL-4) and IL-13 in keratinocytes and fibroblasts, HaCaT cells, a human keratinocyte cell line, and NG1RGB cells, a human skin fibroblast cell line, were used. The expression of TARC protein was measured using enzyme-linked immunosorbent assay (ELISA), and the mRNA level was detected by reverse transcriptase polymerase chain reaction (RT-PCR). The spontaneous expression of TARC protein and mRNA levels were augmented by TNF-alpha and IFN-gamma and were inhibited by IL-4 and IL-13 in the keratinocytes. The fibroblasts expressed the TARC protein and mRNA only in the presence of IL-4+TNF-alpha or IL-13+TNF-alpha stimulation. IFN-gamma further enhanced the IL-4+TNF-alpha or IL-13+TNF-alpha-induced TARC production in the fibroblasts. Thus, TNF-alpha and IFN-gamma -induced TARC production was differentially regulated by IL-4 and IL-13 in human keratinocytes and fibroblasts.

Base Sequence↗

PubMed2002

The pgp1 mutant locus of Arabidopsis encodes a phosphatidylglycerolphosphate synthase with impaired activity.

Phosphatidylglycerol is a ubiquitous phospholipid that is also present in the photosynthetic membranes of plants. Multiple independent lines of evidence suggest that this lipid plays a critical role for the proper function of photosynthetic membranes and cold acclimation. In eukaryotes, different subcellular compartments are competent for the biosynthesis of phosphatidylglycerol. Details on the plant-specific pathways in different organelles are scarce. Here, we describe a phosphatidylglycerol biosynthesis-deficient mutant of Arabidopsis, pgp1. The overall content of phosphatidylglycerol is reduced by 30%. This mutant carries a point mutation in the CDP-alcohol phosphotransferase motif of the phosphatidylglycerolphosphate synthase (EC 2.7.8.5) isoform encoded by a gene on chromosome 2. The mutant shows an 80% reduction in plastidic phosphatidylglycerolphosphate synthase activity consistent with the plastidic location of this particular isoform. Mutant plants are pale green, and their photosynthesis is impaired. This mutant provides a promising new tool to elucidate the biosynthesis and function of plastidic phosphatidylglycerol in seed plants.

Amino Acid Sequence↗

PubMed2002

Prevention and treatment of breast cancer by suppressing aromatase activity and expression.

Estrogen promotes the proliferation of breast cancer cells. Aromatase is the enzyme that converts androgen to estrogen. In tumors, expression of aromatase is upregulated compared to that of surrounding noncancerous tissue. Tumor aromatase is thought to stimulate breast cancer growth in both an autocrine and a paracrine manner. A treatment strategy for breast cancer is to abolish in situ estrogen formation with aromatase inhibitors. In addition, aromatase suppression in postmenapausal women is being evaluated as a potential chemopreventive modality against breast cancer. One area of aromatase research in this laboratory is the identification of foods and dietary compounds that can suppress aromatase activity. In vitro and in vivo studies have found that grapes and mushrooms contain chemicals that can inhibit aromatase. Therefore, a diet that includes grapes and mushrooms would be considered preventative against breast cancer. Another area of our aromatase research is the elucidation of the regulatory mechanism of aromatase expression in breast cancer tissue. Increased aromatase expression in breast tumors is attributed to changes in the transcriptional control of aromatase expression. Whereas promoter I.4 is the main promoter that controls aromatase expression in noncancerous breast tissue, promoters II and I.3 are the dominant promoters that drive aromatase expression in breast cancer tissue. Our recent gene regulation studies revealed that in cancerous versus normal tissue, several positive regulatory proteins (e.g., nuclear receptors and CREB1) are present at higher levels and several negative regulatory proteins (e.g., snail and slug proteins) are present at lower levels. This may explain why the activity of promoters II and I.3 is upregulated in cancerous tissue. In addition, our in vitro transcription/translation analysis using plasmids containing T7 promoter and the human snail gene as a reporter capped with different untranslated exon Is revealed that exon PII-containing transcripts were translated more effectively than were exon I.3-containing transcripts. An understanding of the molecular mechanisms of aromatase expression between noncancerous and cancerous breast tissue, at both transcriptional and translational levels, may help in the design of a therapy based on suppressing aromatase expression in breast cancer tissue.

Aromatase↗

PubMed2002

H1(0) histone and differentiation of dendritic cells. A molecular target for tumor-derived factors.

Dendritic cells (DC) play a central role in antitumor immune responses. Abnormal differentiation of DC and their inability to stimulate T cells are important factors in tumor escape from immune-system control. However, the mechanisms of this process remain elusive. Here, we have described one possible molecular mechanism that involves replacement linker histone H1 (0). A close association between expression of H1(0) and DC differentiation in vitro has been found. DC production in H1(0) -deficient mice was decreased significantly, whereas generation and function of macrophages, granulocytes, and lymphocytes appear to be normal. However, these mice had a significantly reduced response to vaccination with antigens. Tumor-derived factors considerably reduced H1(0) expression in hematopoietic progenitor cells. We have demonstrated that transcription factor NF-kappaB is involved actively in regulation of H1(0). Thus, H1(0) histone may be an important factor in normal DC differentiation. Tumor-derived factors may inhibit DC differentiation by affecting H1(0) expression.

3T3 Cells↗

PubMed2002

[Analysis of three-dimensional microstructure of poly(lactide-co-glycolide) scaffolds made by mild heating under high pressure].

OBJECTIVE: To develop a poly(lactide-co-glycolide)(PLGA) copolymer scaffold with good three-dimensional microstructure and free of organic solvent, which can be used in bone repairing for tissue engineering, and to explore a novel method for developing polymeric scaffolds. METHODS: The polymer and sodium chloride were ground to powder and mixed in 2 different proportions as the materials for preparing the scaffolds by mild heating under high pressure. The porosity and the ratio of open pores in the product were analyzed in light of its density and by sodium chloride approaches, with the pore size, surface and internal structures examined under scanning electron microscope (SEM). RESULTS: The PLGA scaffolds made by this method had porosity of 90 % and 92.5 % respectively, their pore size ranging from 200 to 250 micro m with the ratio of open pores exceeding 98 % (P<0.01). The average sodium chloride leaching time was 12 to 13 h. CONCLUSIONS: The scaffolds made in this way possess stable three-dimensional microstructure with controllable parameters and without cytotoxic effects caused by organic solvent.

Biocompatible Materials↗

PubMed2002

[Current status of study on animal models of osteoporosis].

Animal models of osteoporosis lay the foundation of sophisticated studies on osteoporosis. This article reviews the currently most widely-used animal models of osteoporosis and their essential features, arriving at the conclusion that future studies of osteoporosis will be conducted more and more in large animals as ewes and gilts etc.

Animals↗

PubMed2002

[Surgical treatment of lumbar spinal stenosis associated with unstable degenerative spondylolisthesis].

OBJECTIVES: To assess surgical treatment of lumbar spinal stenosis associated with unstable degenerative spondylolisthesis. METHODS: In 86 patients with lumbar spinal stenosis associated with unstable degenerative spondylolisthesis. (30 men and 56 women, aged from 30 to 77 years), 63 patients complained of lower back pain with both lower extremity pain, 10 patients pain in one leg, and 13 patients only lower back pain. Seventy-two of these patients complained of intermittent claudication, with a walking distance ranging from 10 to 1 000 m. Thirty-two patients had some changes in sensation, motion and reflexes of the foot. According to White' critera, all patients showed dynamic instability of the lesion. Meyerding criteria showed degree 1 in 79 patients, and degree 2 in 7. CT scan was made in 56 patients, MRI in 24 and MRM in 6 before operation. Myelography was performed in 61 patients, and CTM in 6. Stenosis and spondylolisthesis located between L(4) and L(5) in 49 patients, between L(3) and L(4) in 6, between L(5) and S(1) in 25, between L(3) and L(4) and between L(4) and L(5) in 2, and from L(3) to S(1) in 4. The patients with pathological spondylolisthesis were excluded. Lateral recess stenosis of one leg was observed in 10 patients, lateral recess of both legs in 22, and central canal stenosis in 54, of whom 12 patients were associated with protrusion of the lumbar disc. Decompression and autograft with iliac bone and various internal fixation were performed in all patients. RESULTS: The patients were followed up from 8 months to 13 years, longer than 1 year (average 5.6 years) in 81 patients. According to Amundsen et al, excellent results were obtained in 78 patients, good in 5, and fair in 3. Spondylolisthesis was completely reduced in 70 patients of degree 1 (89.9%), and in 6 patients of degree 2 (85.7%). No patient showed slippage aggravated. 74 patients gained bone graft fusion within 3 months and 10 patients within 6 months. Two patients showed pseudoarthrosis during the follow-up. Complications included internal fixation breakage in 1 patient, and delayed infection in 1. CONCLUSIONS: Complete decompression and bone graft fusion are the key to treatment. Decompression and internal fixation improve the symptoms of patients with lumbar spinal stenosis associated with spondylolisthesis. Transpedicle instrumentation can reduce spondylolisthesis and maintain the physical curve of the lumbar.

Adult↗