Biomedical subjects

Yung-Feng Lin

Publications and source records attributed to Yung-Feng Lin.

7 recordsLinked to original sources

PubMed2006

An arsenic metallochaperone for an arsenic detoxification pump.

Environmental arsenic is a world-wide health issue, making it imperative for us to understand mechanisms of metalloid uptake and detoxification. The predominant intracellular form is the highly mephitic arsenite, which is detoxified by removal from cytosol. What prevents arsenite toxicity as it diffuses through cytosol to efflux systems? Although intracellular copper is regulated by metallochaperones, no chaperones involved in conferring resistance to other metals have been identified. In this article, we report identification of an arsenic chaperone, ArsD, encoded by the arsRDABC operon of Escherichia coli. ArsD transfers trivalent metalloids to ArsA, the catalytic subunit of an As(III)/Sb(III) efflux pump. Interaction with ArsD increases the affinity of ArsA for arsenite, thus increasing its ATPase activity at lower concentrations of arsenite and enhancing the rate of arsenite extrusion. Cells are consequently resistant to environmental concentrations of arsenic. This report of an arsenic chaperone suggests that cells regulate the intracellular concentration of arsenite to prevent toxicity.

Arsenic↗

PubMed2005

Type II collagen gene variants and inherited osteonecrosis of the femoral head.

BACKGROUND: Avascular necrosis of the femoral head (ANFH) causes disability that often requires surgical intervention. Most cases of ANFH are sporadic, but we identified three families in which there was autosomal dominant inheritance of the disease and mapped the chromosomal position of the gene to 12q13. METHODS: We carried out haplotype analysis in the families, selected candidate genes from the critical interval for ANFH on 12q13, and sequenced the promoter and exonic regions of the type II collagen gene (COL2A1) from persons with inherited and sporadic forms of ANFH. RESULTS: We identified a G-->A transition in exon 50 of COL2A1 in affected members of a four-generation family with ANFH. This transition predicts the replacement of glycine with serine at codon 1170 in a GXY repeat of type II collagen. Another pedigree was shown to harbor the same transition, but the mutant allele occurred on a different haplotype background. In a third family, a G-->A transition in exon 33 of the gene, causing a glycine-to-serine change at codon 717, was detected. No mutation was found in the COL2A1 coding region in sporadic cases of ANFH. CONCLUSIONS: All the patients with familial ANFH whom we studied carried COL2A1 mutations. In families with ANFH, haplotype and sequence analysis of the COL2A1 gene can be used to identify carriers of the mutant allele before the onset of clinical symptoms, allowing the initiation of measures that may delay progression of the disease.

Adult↗

PubMed2004

High frequency of epidermal growth factor receptor mutations with complex patterns in non-small cell lung cancers related to gefitinib responsiveness in Taiwan.

PURPOSE: Epidermal growth factor receptor (EGFR) mutations related to gefitinib responsiveness in non-small cell lung cancer have been found recently. Detection of EGFR mutations has become an important issue for therapeutic decision-making in non-small cell lung cancer. EXPERIMENTAL DESIGN: Mutational analysis of the kinase domain of EGFR coding sequence was done on 101 fresh frozen tumor tissues from patients without prior gefitinib treatment and 16 paraffin-embedded tumor tissues from patients treated with gefitinib. Detection of phosphorylated EGFR by immunoblot was also done on frozen tumor tissues. RESULTS: The 101 non-small cell lung cancer tumor specimens include 69 adenocarcinomas, 24 squamous cell carcinomas, and 8 other types of non-small cell lung cancers. Mutation(s) in the kinase domain (exon 18 to exon 21) of the EGFR gene were identified in 39 patients. All of the mutations occurred in adenocarcinoma, except one that was in an adenosquamous carcinoma. The mutation rate in adenocarcinoma was 55% (38 of 69). For the 16 patients treated with gefitinib, 7 of the 9 responders had EGFR mutations, and only 1 of the 7 nonresponders had mutations, which included a nonsense mutation. The mutations seem to be complex in that altogether 23 different mutations were observed, and 9 tumors carried 2 mutations. CONCLUSIONS: Data from our study would predict a higher gefitinib response rate in lung adenocarcinoma patients in Chinese and, possibly, other East Asian populations. The tight association with adenocarcinoma and the high frequency of mutations raise the possibility that EGFR mutations play an important role in the tumorigenesis of adenocarcinoma of lung, especially in East Asians.

Adenocarcinoma↗

PubMed2004

A simple radical addition-elimination route to geometrically pure (E)-alkene and chromanone derivatives via beta-nitrostyrene.

Various geometrically pure (E)-beta-alkyl-styrenes have been synthesized by the radical NO(2) substitution of alkyl moieties generated via hydrogen abstraction followed by decarbonylation from aliphatic aldehydes. These reactions, which involve a high chemical selectivity and regioselectivity constitute a new route to (E)-beta-alkylstyrenes. Both aliphatic and aromatic aldehydes can be used in this novel reaction. When 2-allyloxybenzaldehyde was used, the benzoyl radical added directly to the double bond without decarbonylation to give the 3-cinnamylchroman-4-one. This unique difference between aliphatic and aromatic aldehydes represents a simple route for the synthesis of biologically important chromanones.

Journal Article↗

PubMed2004

Genomic shotgun array: a procedure linking large-scale DNA sequencing with regional transcript mapping.

To facilitate transcript mapping and to investigate alterations in genomic structure and gene expression in a defined genomic target, we developed a novel microarray-based method to detect transcriptional activity of the human chromosome 4q22-24 region. Loss of heterozygosity of human 4q22-24 is frequently observed in hepatocellular carcinoma (HCC). One hundred and eighteen well-characterized genes have been identified from this region. We took previously sequenced shotgun subclones as templates to amplify overlapping sequences for the genomic segment and constructed a chromosome-region-specific microarray. Using genomic DNA fragments as probes, we detected transcriptional activity from within this region among five different tissues. The hybridization results indicate that there are new transcripts that have not yet been identified by other methods. The existence of new transcripts encoded by genes in this region was confirmed by PCR cloning or cDNA library screening. The procedure reported here allows coupling of shotgun sequencing with transcript mapping and, potentially, detailed analysis of gene expression and chromosomal copy of the genomic sequence for the putative HCC tumor suppressor gene(s) in the 4q candidate region.

Cell Line, Tumor↗

PubMed2002

The soft metal ion binding sites in the Staphylococcus aureus pI258 CadC Cd(II)/Pb(II)/Zn(II)-responsive repressor are formed between subunits of the homodimer.

The Staphylococcus aureus plasmid pI258 CadC is a homodimeric repressor that binds Cd(II), Pb(II), and Zn(II) and regulates expression of the cadAC operon. CadC binds two Cd(II) ions per dimer, with a tetrathiolate binding site composed of residues Cys(7), Cys(11), Cys(58), and Cys(60). It is not known whether each site consists of residues from a single monomer or from residues contributed by both subunits. To examine whether Cys(7) and Cys(11) are spatially proximate to Cys(58) and Cys(60) of the same subunit or of the other subunit, homodimers with the same cysteine mutation in each subunit and heterodimers containing different cysteine mutations in the two subunits were reacted with 4,6-bis(bromomethyl)-3,7-dimethyl-1,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-dione, which cross-links thiol groups that are within 3-6 A of each other. Cys(7) or Cys(11) cross-linked only with Cys(58) or Cys(60) on the other subunit. The data demonstrate that Cys(7) and Cys(11) from one monomer are within 3-6 A of either Cys(58) or Cys(60) in the other monomer. The results of this study strongly indicate that each of the two Cd(II) binding sites in the CadC homodimer is composed of Cys(7) and Cys(11) from one monomer and Cys(58) and Cys(60) from the other monomer.

Amino Acid Sequence↗

PubMed2002

Membrane topology of the p1258 CadA Cd(II)/Pb(II)/Zn(II)-translocating P-type ATPase.

Plasmid p1258 carries the cadA gene that confers resistance to cadmium, lead, and zinc. CadA catalyzes ATP-dependent cadmium efflux from cells of Staphylococcus aureus. It is a member of the superfamily of P-type ATPases and belongs to the subfamily of soft metal ion pumps. In this study the membrane topology of this P-type ATPase was determined by constructing fusions with the topological reporter genes phoA or lacZ. A series of 44 C-terminal truncated CadAs were fused with one or the other reporter gene, and the activity of each chimeric protein was determined. In addition, the location of the first transmembrane segment was determined by immunoblot analysis. The results are consistent with the p1258 CadA ATPase having eight transmembrane segments. The first 109 residues is a cytosolic domain that includes the Cys(X)2Cys motif that distinguishes soft metal ion-translocating P-type ATPases from their hard metal ion-translocating homologues. Another feature of soft metal ion P-type ATPases is the CysProCys motif, which is found in the sixth transmembrane segment of CadA. The phosphorylation site and ATP binding domain conserved in all P-type ATPases are situated within the large cytoplasmic loop between the sixth and seventh transmembrane segments.

Adenosine Triphosphatases↗