Biomedical subjects

Chen-Kung Chou

Publications and source records attributed to Chen-Kung Chou.

24 records · Page 2Linked to original sources

PubMed2003

The A20-binding protein ABIN-2 exerts unexpected function in mediating transcriptional coactivation.

The human ABIN-2 was originally identified as an A20-associating cytosolic protein to block NF-kappaB activation induced by various stimuli. Here we report that ABIN-2 has the potential to enter the nucleus and plays a role in mediating transcriptional activation in both yeast and mammalian cells. The Gal4BD-ABIN-2 fusion protein is able to drive the expression of the GAL4-responsive reporter gene in yeast efficiently without the need of the Gal4p activation domain, suggesting that ABIN-2 functions as a transcriptional coactivator and facilitates transcription in yeast. In contrast to the activity in yeast, however, only the C-terminal fragment of ABIN-2 exerts the transactivating activity in mammalian cells but not the full-length ABIN-2 protein. This observation has led to the identification of the N-terminal 195 amino acids of ABIN-2 as a regulatory domain, which retains the full-length ABIN-2 in the cytoplasm of mammalian cells and thus cannot transactivate. We have also found that BAF60a, a component of chromatin-remodeling complex, interacts with ABIN-2 by the yeast two-hybrid analysis. Together, our results suggest that the nuclear ABIN-2 defines a novel transcriptional coactivator and acts presumably by recruiting a chromatin-remodeling complex to the site of the target gene.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Identification of a novel cell cycle regulated gene, HURP, overexpressed in human hepatocellular carcinoma.

An analytic strategy was followed to identify putative regulatory genes during the development of human hepatocellular carcinoma (HCC). This strategy employed a bioinformatics analysis that used a database search to identify genes, which are differentially expressed in human HCC and are also under cell cycle regulation. A novel cell cycle regulated gene (HURP) that is overexpressed in HCC was identified. Full-length cDNAs encoding the human and mouse HURP genes were isolated. They share 72 and 61% identity at the nucleotide level and amino-acid level, respectively. Endogenous levels of HURP mRNA were found to be tightly regulated during cell cycle progression as illustrated by its elevated expression in the G(2)/M phase of synchronized HeLa cells and in regenerating mouse liver after partial hepatectomy. Immunofluorescence studies revealed that hepatoma up-regulated protein (HURP) localizes to the spindle poles during mitosis. Overexpression of HURP in 293T cells resulted in an enhanced cell growth at low serum levels and at polyhema-based, anchorage-independent growth assay. Taken together, these results strongly suggest that HURP is a potential novel cell cycle regulator that may play a role in the carcinogenesis of human cancer cells.

Amino Acid Sequence↗

PubMed2003

Overexpression of a novel imprinted gene, PEG10, in human hepatocellular carcinoma and in regenerating mouse livers.

Many of the promising applications of the microarray technology are pertinent to identifying abnormalities in gene expression that contribute to malignant progression. We developed a bioinformatics tool to identify differentially expressed genes in human hepatocellular carcinoma (HCC). This involved the construction of a liver EST database (http://lestdb.nhri.org.tw) and in silico verification of differentially expressed genes with a human hepatoma microarray database. The stringency of the search was reinforced with a statistical analysis. A novel imprinted gene, paternally expressed 10(PEG10) was identified as having an elevated level of expression in the majority of the HCC samples and was also induced to express during G2/M phase of regenerating mouse liver. Ectopic expression of PEG10 in 293T cells affects cell cycle progression. PEG10 is distributed in the cytosol and associates with the nuclear membrane. This is the first time that an imprinted gene has been found to reexpress in both human HCC and in the regenerating mouse liver. This result indicates that the induction of the paternally imprinted gene may play an important role during liver regeneration or carcinogenesis of the human hepatocyte. Understanding the molecular basis of the abnormal imprinting of PEG10 will shed new light on the process that leads to liver disease.

Animals↗

PubMed2002

Potential molecular marker for detecting transitional cell carcinoma.

OBJECTIVES: To assess the expression rate of a cancer-related gene, hepatoma-up-regulated protein (HURP), in the tumor tissue of transitional cell carcinoma (TCC), and to assess the potential suitability of using this gene as a novel molecular marker for detecting TCC in voided urine. METHODS: Total RNA was extracted from 80 TCC tissue samples of the urinary tract. Forty-five of the 80 tumor-adjacent tissue samples were from the same patients and 15 were from control subjects (patients with benign prostatic hyperplasia). The expression levels of HURP mRNA in these specimens were examined using reverse transcriptase-polymerase chain reaction. The HURP mRNA transcripts in voided urine pellets from 14 additional patients were determined using the same method. The messages were normalized to beta-actin mRNA. RESULTS: The detection of HURP expression in the TCC tissue samples had a sensitivity of 88.8% (71 of 80) and a specificity of 100% (15 of 15). Ten of the 45 grossly tumor-adjacent tissue samples expressed HURP mRNA, which may indicate subtle genetic changes in tissue adjacent to tumor. All seven urine specimens from the patients with TCC revealed HURP expression; however, no specimens from patients with nonmalignant diseases did so. CONCLUSIONS: A potential molecular marker for detecting TCC with tissue specimens and voided urine samples has been found. Although the real clinical application of this marker requires additional evaluation, the high sensitivity and specificity of the HURP gene amplification method warrants more investigation in the future.

Biomarkers, Tumor↗

PubMed2002

In vitro action of carboxyfullerene.

Fullerene compounds have avid reactivity with free radicals and are regarded as 'radical sponges'. The trimalonic acid derivative of fullerene is one of the water-soluble compounds that has been synthesized and found to be an effective antioxidant both in vivo and in vitro. Carboxyfullerene has been shown to be effective in the treatment of both Gram-positive and -negative infections, although its mode of action is poorly understood. We determined the MIC and minimal bactericidal concentration of carboxyfullerene for 20 isolates, including Staphylococcus spp., Streptococcus spp., Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Klebsiella pneumoniae. We further investigated the action of carboxyfullerene using transmission electron microscopy (TEM), anticarboxyfullerene antibody binding assay and a membrane perturbation assay. All Gram-positive species were inhibited by < or = 50 mg/L of carboxyfullerene, whereas Gram-negative species were not inhibited, even at 500 mg/L carboxyfullerene. Bactericidal activity was demonstrated only for Gram-positive species, particularly for Streptococcus pyogenes A-20, which was killed rapidly. Intercalation of carboxyfullerene into the cell wall of staphylococci and streptococci was demonstrated by TEM and anti-carboxyfullerene binding assay. Damage to the cell membrane in Gram-positive, but not Gram-negative, bacteria was confirmed by the membrane perturbation assay. These findings indicate that the action of carboxyfullerene on Gram-positive bacteria is achieved by insertion into the cell wall and destruction of membrane integrity.

Anti-Bacterial Agents↗

PubMedDate not supplied

An LKB1-interacting protein negatively regulates TNFalpha-induced NF-kappaB activation.

The Peutz-Jeghers syndrome (PJS) is a hereditary disorder that predisposes an individual to benign and malignant tumors in multiple organ systems. Recently, the locus responsible for PJS was mapped genetically to the LKB1 gene, with a subsequent investigation proving that it is responsible for most cases of PJS. LKB1 encodes a nuclear serine/threonine protein kinase, and potential tumor-suppressing activity has been attributed to LKB1 kinase. However, how LKB1 exerts its tumor-suppressing function remains to be determined. In this report, we describe the identification of a putative human LKB1-interacting protein, FLIP1, using the yeast two-hybrid system. Two regions of the LKB1 sequence have been determined to be crucial for the interaction with FLIP1. FLIP1 encodes a protein of 429 amino acids with a predicted molecular weight of 47 kd. In contrast to LKB1, which is mainly nuclear, FLIP1 is a cytoplasmic protein, and its expression is ubiquitous in all human tissues examined to date. Interestingly, deletion of the 195 N- terminal amino acids allows FLIP1 to enter the nucleus, suggesting the presence of a regulatory mechanism through its N-terminus for nuclear entry. In addition, we found that ectopic expression of FLIP1 selectively blocks cytokine-induced NF-kappaB activation. The involvement of FLIP1 in the regulation of NF-kappaB activity may shed new light on the role of LKB1 in tumor suppression.

AMP-Activated Protein Kinase Kinases↗