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B Liao

Publications and source records attributed to B Liao.

16 recordsLinked to original sources
PubMed2001

c-Fos oncogene regulator Elk-1 interacts with BRCA1 splice variants BRCA1a/1b and enhances BRCA1a/1b-mediated growth suppression in breast cancer cells.

Elk-1, a c-Fos protooncogene regulator, which belongs to the ETS-domain family of transcriptional factors, plays an important role in the induction of immediate early gene expression in response to a variety of extracellular signals. In this study, we demonstrate for the first time the in vitro and in vivo interaction of Elk-1 with BRCA1 splice variants BRCA1a and BRCA1b using GST-pull down assays, co-imunoprecipitations/Western blot analysis of cell extracts from breast cancer cells and mammalian two-hybrid assays. We have localized the BRCA1 interaction domain of Elk-1 protein to the conserved ETS domain, a motif involved in DNA binding and protein-protein interactions. We also observed binding of BRCA1 proteins to other ETS-domain transcription factors SAP1, ETS-1, ERG-2 and Fli-1 but not to Elk-1 splice variant DeltaElk-1 and c-Fos protooncogene. Both BRCA1a and BRCA1b splice variants function as growth suppressors of human breast cancer cells. Interestingly, our studies reveal that although both Elk-1 and SAP-1 are highly homologous members of a subfamily of ETS domain proteins called ternary complex factors, it is only Elk-1 but not SAP-1 that can augment the growth suppressive function of BRCA1a/1b proteins in breast cancer cells. Thus Elk-1 could be a potential downstream target of BRCA1 in its growth control pathway. Furthermore, we have observed inhibition of c-Fos promoter activity in BRCA1a transfected stable breast cancer cells and over expression of BRCA1a/1b attenuates MEK-induced SRE activation in vivo. These results demonstrate for the first time a link between the growth suppressive function of BRCA1a/1b proteins and signal transduction pathway involving Elk-1 protein. All these results taken together suggest that one of the mechanisms by which BRCA1a/1b proteins function as growth/tumor suppressors is through inhibition of the expression of Elk-1 target genes like c-Fos.

Alternative Splicing↗
PubMed2001

Isolation of cDNA and genomic DNA clones encoding a calmodulin-binding protein related to a family of ATPases involved in cell division and vesicle fusion.

Calmodulin (CaM), a primary Ca2+ receptor in all eukaryotic cells, is a multifunctional protein that functions by interacting with and modulating the activities of a wide variety of target proteins. Identifying and characterizing these CaM-binding target proteins is essential to define the pathways by which Ca(2+)-regulated signals are transduced. An Arabidopsis thaliana L. flower cDNA expression library constructed in lambda ZAPII was screened for CaM-binding proteins with 35S-labeled CaM. A partial cDNA whose encoded protein shares a high level of similarity with yeast CDC48p was isolated. A genomic clone was isolated using the partial length cDNA clone as a probe, and its nucleotide sequence was determined. The genomic DNA sequence was used to design oligonucleotide primers for polymerase-chain-reaction (PCR) experiments that facilitated cloning and reconstructing a full-length, 3.4-kb cDNA clone. The cDNA encodes a 111-kDa CaM-interacting protein (CIP111) containing motifs characteristic of a diverse family of ATPases, including proteins involved in cell cycle regulation, protein degradation, and vesicle-mediated protein transport. A truncated fusion protein encoded by the carboxy-terminal region of CIP111 was produced in Escherichia coli and shown to bind CaM in a Ca(2+)-dependent manner by protein gel blot and affinity chromatography binding assays. Reverse-transcription PCR analyses demonstrated that CIP111 mRNA is expressed in all organs examined including flowers, siliques, floral stalks, leaves, and roots. DNA blot hybridization analyses indicate that a single-copy gene in Arabidopsis is likely to encode CIP111.

Adenosine Triphosphatases↗
PubMed2001

[Study on the relation between the angiotensin converting enzyme gene and pregnancy induced hypertension].

OBJECTIVE: To study the relationship between the 16th intron insertion/deletion (I/D) polymorphism of angiotensin converting enzyme (ACE) gene and pregnancy induced hypertension (PIH). METHODS: The 16th intron I/D polymorphism of ACE gene in 60 PIH women (PIH group) and 50 normal pregnant women (control group) was detected by PCR. The type of ACE gene in PIH group was assessed and the serum concentration of angiotensin II (AngII) was compared between PIH group and control group. RESULTS: ACE gene types in the PIH women included: insertion homozygote II, deletion homozygote (DD) and insertion/deletion heterozygote (ID). The gene frequency was 55.0% (33/60) for II, 26.7% (16/60) for ID and 18.3% (11/60) for DD respectively. The frequency of insertion allelotype (0.7) of PIH group was higher than that of control group (0.3) (P < 0.05). The Ang II concentration in DD type PIH women was higher than that in control group although the Ang II concentration in II type and I D type PIH was not different from control. CONCLUSIONS: ACE gene polymorphism in the PIH women included: insertion homozygote II, deletion homozygote (DD) and insertion/deletion heterozygote (ID). The concentration of Ang II in DD type PIH women was higher than in control. It is suggested that the pathogenesis of PIH may be connected with multiple genes and factors.

Adult↗
PubMed2000

MAD: a suite of tools for microarray data management and processing.

SUMMARY: Microarray data management and processing (MAD) is a set of Windows integrated software for microarray analysis. It consists of a relational database for data storage with many user-interfaces for data manipulation, several text file parsers and Microsoft Excel macros for automation of data processing, and a generator to produce text files that are ready for cluster analysis. AVAILABILITY: Executable is available free of charge on http://pompous.swmed.edu. The source code is also available upon request.

Databases, Factual↗
PubMed1999

Mechanism of Ca2+-dependent nuclear accumulation of calmodulin.

The intracellular Ca2+ receptor calmodulin (CaM) coordinates responses to extracellular stimuli by modulating the activities of its various binding proteins. Recent reports suggest that, in addition to its familiar functions in the cytoplasm, CaM may be directly involved in rapid signaling between cytoplasm and nucleus. Here we show that Ca2+-dependent nuclear accumulation of CaM can be reconstituted in permeabilized cells. Accumulation was blocked by M13, a CaM antagonist peptide, but did not require cytosolic factors or an ATP regenerating system. Ca2+-dependent influx of CaM into nuclei was not blocked by inhibitors of nuclear localization signal-mediated nuclear import in either permeabilized or intact cells. Fluorescence recovery after photobleaching studies of CaM in intact cells showed that influx is a first-order process with a rate constant similar to that of a freely diffusible control molecule (20-kDa dextran). Studies of CaM efflux from preloaded nuclei in permeablized cells revealed the existence of three classes of nuclear binding sites that are distinguished by their Ca2+-dependence and affinity. At high [Ca2+], efflux was enhanced by addition of a high affinity CaM-binding protein outside the nucleus. These data suggest that CaM diffuses freely through nuclear pores and that CaM-binding proteins in the nucleus act as a sink for Ca2+-CaM, resulting in accumulation of CaM in the nucleus on elevation of intracellular free Ca2+.

Adenosine Triphosphate↗
PubMed1999

[A comparative study of HLA-A locus in northern and southern Chinese by means of PCR/SSOP typing]

OBJECTIVE: To compare the HLA-A locus in a population selected from Beijing (northern group) with that in a population selected from Guangzhou (southern group). METHODS: HLA typing was performed by using PCR/SSOP method. A pair of primer and 54 probes were used. RESULTS: In 18 alleles identified, the differences in gene frequency between northern and southern Chinese were found. In northern group, A*0205, 0210 and 2901 were absent, and the frequencies of A*2601, 3001 and 3101 were higher than those of southern group; while in southern group, A*3103, 3201 and 6801 were absent, the frequencies of A*0203 and 1101 were higher than those of northern group; and in addition, six subtypes of A2 serological specificity, namely A*0201, 0203, 0205, 0206, 0207 and 0210, were found, in which A*0201 predominated. CONCLUSION: There are some differences in the genetic background of northern and southern Chinese. A2 subtypes have important implications for unrelated-donor transplantation.

Journal Article↗
PubMed1999

[A comparative study of HLA-A locus in northern and southern Chinese bymeans of PCR/SSOP typing].

OBJECTIVE: To compare the HLA-A locus in a population selected from Beijing (northern group) with that in a population selected from Guangzhou (southern group). METHODS: HLA typing was performed by using PCR/SSOP method. A pair of primer and 54 probes were used. RESULTS: In 18 alleles identified, the differences in gene frequency between northern and southern Chinese were found. In northern group, A*0205, 0210 and 2901 were absent, and the frequencies of A*2601, 3001 and 3101 were higher than those of southern group; while in southern group, A*3103, 3201 and 6801 were absent, the frequencies of A*0203 and 1101 were higher than those of northern group; and in addition, six subtypes of A2 serological specificity, namely A*0201, 0203, 0205, 0206, 0207 and 0210, were found, in which A*0201 predominated. CONCLUSION: There are some differences in the genetic background of northern and southern Chinese. A2 subtypes have important implications for unrelated-donor transplantation.

Alleles↗
PubMed1998

Psoralen photochemotherapy, clinical efficacy, and photomutagenicity: the role of molecular epidemiology in minimizing risks.

Photochemotherapy employing 8-methoxypsoralen and ultraviolet radiation (PUVA) is widely used in the treatment of psoriasis. The photoactivation of psoralens in skin cells leads to DNA photoadduct formation which may be responsible for the efficacy of PUVA. Subsequent mutations may lead to the increased incidence of squamous cell carcinoma (SCC). Mutations in the p53 tumor suppressor gene have been detected in many human cancers. In this review, p53 mutation spectra in murine and human SCC are compared to those obtained from murine cells and skin treated with PUVA as well as to the p53 mutation spectrum in human solar SCC. While the expected psoralen-type mutations at alternating AT sites were detected in the treated cells and murine SCC (average frequency > 40%), such mutations were not commonly detected in the human SCC (< 10%). Other common mutations in the human SCC included: CG-->TA transitions (18%) and CG-->AT and TA-->GC transversions (17 and 25%, respectively). In addition, the frequency of UVB-type mutations at dipyrimidine sites (CC-->TT) in the SCC PUVA-treated psoriasis patients was comparable to that in patients with SCC from only solar exposure. A review of therapeutic history of these patients showed that many had also received UVB phototherapy. Furthermore, because sunlight is thought to be beneficial for psoriasis, nontherapeutic, casual UVB exposure cannot be excluded. Thus, the PUVA SCC may have arisen from the solar mutations and PUVA may enhance tumor progression by other epigenetic effects.

Ficusin↗
PubMed1996

Differential stimulation of NAD kinase and binding of peptide substrates by wild-type and mutant plant calmodulin isoforms.

Calmodulin from Arabidopsis thaliana consists of at least four isoforms, which differ in their deduced amino acid sequences by as many as six conservative substitutions. To determine whether these differences are biochemically significant, cDNAs encoding three of the four isoforms were engineered to produce recombinant proteins in Escherichia coli, purified to apparent homogeneity, and assayed for their abilities to activate pea leaf NAD kinase in vitro. The CaM-2 isoform was a significantly more efficient activator of NAD kinase compared with the CaM-4 and -6 isoforms based on both the apparent Vmax it elicited and the K0.5 activation. These results are consistent with the hypothesis that the Arabidopsis CaM isoforms have evolved to optimize the protein's interaction with different Ca2+/CaM-regulated target enzymes. The ability to activate NAD kinase was also investigated for a carboxy-terminal nonsense mutant of CaM-6 (CaM-6M), which substituted 14 hydrophilic amino acids for a region of seven amino acids that normally form an exposed hydrophobic surface when wt CaM-6 binds Ca2+. CaM-6M-activated NAD kinase displayed an apparent V. that was reduced 40% and a K0.5 that was an order of magnitude greater than the CaM-6-activated enzyme. The Ca2+-dependence of CaM-GM to activate NAD kinase was identical to that of CaM-6, but CaM-6M bound synthetic peptide substrates with lower apparent affinity than did CaM-6. Thus, the carboxy-terminal hydrophobic domain of CaM appears to be critical for its interaction with NAD kinase. In contrast, amino-terminal fusions of a hydrophilic, alpha-helical 12-residue c-myc epitope tag to CaM-2 and -4 yielded proteins that activated NAD kinase to apparent Vmax values within 10% of those obtained with the wild-type CaM proteins.

Amino Acid Sequence↗
PubMed1996

Calmodulin isoforms differentially enhance the binding of cauliflower nuclear proteins and recombinant TGA3 to a region derived from the Arabidopsis Cam-3 promoter.

Many stimuli increase cytoplasmic Ca2+ concentrations as an early signal transduction event and alter the patterns of nuclear gene transcription, but the mechanisms by which Ca2+ signals are transduced to the nucleus are not known. This article shows that at least four DNA binding proteins from cauliflower nuclear extracts are also calmodulin (CaM) binding proteins. CaM enhances the binding of these proteins to a C/G-box sequence element in the Arabidopsis Cam-3 promoter. Binding to the C/G-box is enhanced preferentially by the CaM isoform encoded by Cam-3. However, it is not clear whether the effect is mediated directly by CaM or indirectly through the activity of a CaM-regulated protein phosphatase. CaM also binds recombinant TGA3 and enhances its binding to the same Cam-3 promoter element. These results are consistent with the idea that a Ca(2+)-mediated signalling pathway eliciting some changes in gene expression may consist of CaM, or a structurally related Ca2+ binding protein, and transcription factors.

Arabidopsis↗
PubMed1994

Dexamethasone reverses adrenalectomy-induced neuronal de-differentiation in midbrain raphe-hippocampus axis.

Differentiation leads to specific morphological and biochemical characteristics. We examined whether epigenetic factors (e.g., glucocorticoids) are required to maintain neuronal differentiation in the adult brain. In the midbrain, adrenalectomy (ADX) (1-2 wk) reduced the size of tryptophan hydroxylase (WH)-immunoreactive (IR) neurons. ADX rats exposed to short-term (24-72-h) dexamethasone (ST-DEX) in the drinking saline (10 mg/l) showed an increase in WH protein, somal area and dendritic size of WH-IR neurons. In the hippocampus, ADX for 2-3 mo (long-term; LT) reduced Nissl staining, calbindin (CBD)-IR and 5-HT1A receptor mRNA in the granular cell layer, and the size of the molecular layer and its CBD-IR dendrites. Small vimentin (Vim)-IR glial cells emerged in the granular layer. ST-DEX after LT-ADX rapidly induced a recovery of 5-HT1A mRNA, Nissl labeling and CBD-IR in the granule cell layer. In the molecular layer, there was an increase in the area and in the number of CBD-IR dendrites. Furthermore, the Vim-IR glial cells were enlarged in size and branching. The rate of cell proliferation was studied in these animals. Immunostaining with antibodies against proliferating cell nuclear antigen (PCNA) and use of bromouridine argue against enhanced neurogenesis after ST-DEX in LT-ADX. We propose that glucocorticoids induce and maintain differentiation of serotonergic and CBD-IR neurons in the midbrain-hippocampal axis. A neuronotrophic role for the glial 5-HT1A receptor is suggested.

Adrenalectomy↗
PubMed1993

Loss of 5-HT1A receptor mRNA in the dentate gyrus of the long-term adrenalectomized rats and rapid reversal by dexamethasone.

Two months after bilateral adrenalectomy, 5-HT1A receptor mRNA labelling was decreased in the granular cell layer of the dentate gyrus but not in the pyramidal cell layer of Ammon's horn. Two month adrenalectomized rats given dexamethasone (10 micrograms/ml saline) 24 or 72 h before perfusion showed a progressive recovery in 5-HT1A mRNA labelling in the dentate gyrus. 5-HT1A expression may underlie hippocampal neuronal plasticity after long-term adrenalectomy.

Adrenalectomy↗
PubMed1993

Increase of tryptophan hydroxylase enzyme protein by dexamethasone in adrenalectomized rat midbrain.

Using two specific anti-peptide antibodies (WH-66 and WH-412) against tryptophan hydroxylase (TPH or WH), a single principle band from the midbrain raphe area was seen (approximately 49 kDa) in immunoblots. Densitometric comparison of the immunoreactivity of the 49 kDa band was greater (50-75%) in immunoblots of midbrain raphe samples from adrenalectomized (ADX) rats given dexamethasone (DEX) in their drinking water (10 mg/liter) for 12-96 hr. No difference from ADX brains was seen in the 49 kDa band after only 4 hr of exposure to DEX in the drinking water. Immunocytochemical staining with WH-66 of sections from rat brainstem showed specific cellular staining in all of the serotonergic raphe nuclei but not in substantia nigra or locus coeruleus. More cellular staining of WH-66-immunoreactive (WH-66-IR) cells was observed in the dorsal and median raphe nuclei in ADX rats given DEX for 72 hr, especially in the perikarya and in the primary dendrites. Quantification of staining per cell soma with an automatic image analyzer indicates that amount of WH-66-IR in neurons from both the lateral wing subdivision of the dorsal raphe nucleus and in the supralemniscal nucleus, B-9, was 80% higher in the ADX+DEX compared to ADX animals. Interestingly, morphometric analysis of these same cells showed a corresponding increase of 37-80% in somal area. It is suggested that a part of the increase in TPH/WH staining may be a consequence of cellular hypertrophy due to DEX treatment of the ADX rats.

Adrenal Glands↗