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C W Chen

Publications and source records attributed to C W Chen.

At least 145 records · Page 8Linked to original sources
PubMed1988

A trans-acting gene is required for the phenotypic expression of a tyrosinase gene in Streptomyces.

The melanin locus (melC) from Streptomyces antibioticus was previously shown to be composed of two open reading frames (ORFs), melC1 and melC2. The melC2 ORF codes for the polypeptide chain of tyrosinase (apotyrosinase). The function of melC1 is not known except that insertional mutation within it abolishes the tyrosinase activity. Here, we show that in Streptomyces lividans TK64 harboring melC1 mutated and melC2 intact (melC1- melC2+) plasmids, while there was no tyrosinase activity, melC transcript was synthesized and apotyrosinase could be detected. The apotyrosinase could be activated to a limited degree by incubation with copper ions, or by mixing the mycelial extract from a culture harboring a melC1- melC2+ (pPF950) plasmid with that from a culture containing a melC1+ melC2- (pSA1) plasmid. Complementation analysis showed that melC1 acted in trans on the tyrosinase gene expression. Together, these results suggest that melC1 encodes or regulates a copper-transfer protein serving an in vivo copper-donor function in the biosynthesis of active tyrosinase.

Catechol Oxidase↗
PubMed1988

Arthrobacter viscosus DNA is modified at GATC sequence.

Arthrobacter viscosus DNA was resistance to digestion by restriction enzymes that are sensitive to methylation of the cytosine residue (but not of adenine) within the GATC recognition sequence. Restriction enzymes sensitive to methylation of cytosine in other recognition sequences were not affected. A. viscosus DNA thus appeared to contain methylated cytosine specifically at the GATC sequence.

Animals↗
PubMed1987

Levels of high energy phosphates in human lung cancer cell lines by 31P nuclear magnetic resonance spectroscopy.

Human lung cancers are divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) based on established criteria. SCLC differs from NSCLC by the expression of biomarkers, including creatine kinase-BB isoenzyme (EC 2.7.3.2). Subtypes of SCLC are referred to as classic and variant, both of which have elevated levels of creatine kinase-BB isoenzyme. We, therefore, applied 31P nuclear magnetic resonance spectroscopy to cell lines of classic SCLC, variant SCLC, and NSCLC human tumors, using continuous perfusion to identify any differences in the detectable levels of intracellular high-energy phosphate compounds. The spectra indicate that only the variant SCLC cells maintain high levels of phosphocreatine. Additionally, the classic SCLC cells express elevated levels of a diphosphodiester. Neither phosphocreatine nor diphosphodiesters are found in the NSCLC cell spectra.

Adenosine Triphosphate↗
PubMed1987

Intraplasmid recombination in Streptomyces lividans 66.

An Escherichia coli-Streptomyces shuttle plasmid pIF132 containing two direct mel repeats was constructed. While pIF132 replicated relatively stably in E. coli (Rec+ or recA), its structure was unstable in S. lividans: recombination between the mel repeats resulted in a smaller plasmid, pIF138. Furthermore, pIF132 formed oligomers extensively in E. coli but not in S. lividans.

DNA Restriction Enzymes↗
PubMed1987

Isolation and characterization of Streptomyces lividans mutants deficient in intraplasmid recombination.

Plasmid pIF132 containing two direct repeats of the mel (melanin) sequence was used to monitor intraplasmid recombination. Five mutants of Streptomyces lividans TK64 deficient in intraplasmid recombination were isolated. Four contained additional defects in aerial mycelium formation, pigmentation, and nutrient requirements; among these two showed extensive amplification of chromosomal sequences. Mutant JT46 had no pleiotropic defects but had the most severe blockage in recombination. Only one of the mutants was slightly more sensitive to UV and two were slightly more sensitive to mitomycin C. Plasmid pWCL1 (containing pIJ702, pUC12, and HBVsAg sequences; Lee et al. 1986) could not stably replicate in TK64 without spontaneous deletions. In contrast the mutant JT46 maintained the integrity of pWCL1 much more stably.

DNA Repair↗
PubMed1987

Comparative studies on aetiology and epidemiology of viral conjunctivitis in three countries of East Asia--Japan, Taiwan and South Korea.

A total number of 1105 cases with viral conjunctivitis, mainly epidemic kerato-conjunctivitis (EKC) consisting of 354 cases from Sapporo, Japan, of 628 from Kaohsiung, Taiwan and of 123 from Busan, Korea, encountered during the periods, 1980-81 and/or 1983, were studied aetiologically and epidemiologically. Patients were aged from 27 days to 88 years with a peak in the 20-29 year age group. Aetiological diagnoses were established in 610 cases (55%), consisting of 536 cases (49%) caused by adenoviruses and of 74 (7%) by EV 70. The most frequently detected agent was Ad 8 (57%), followed by EV 70 (12%), Ad 3 (9%) and Ad 19 (7%). The aetiological profiles of viral conjunctivitis were generally similar in three cities of East Asia. EKC (70%) was mainly caused by Ad 8, Ad 19 and Ad 37, but AHC (13%) by EV 70 and PCF (5%) by Ad 3 and Ad 11. Ad 19 and Ad 37 isolates in three cities were compared with the cleavage patterns with restriction endonucleases, BamHl, Smal, Sall and Hindlll. All of the Ad 19 isolates tested were identical to Ad 19a reported by Wadell et al, and all but three isolates of Ad 37 were identical to the Ad 37 prototype prevalent in Europe and the US. The three isolates of Ad 37, different from the prototype in cleavage pattern with Hindlll, designated as Ad 37A, were detected in Sapporo and Kaohsiung in 1980. From the cleavage patterns with four restriction endonucleases, Hindlll, BamHl, Sa1l and Sstl, the Ad 8 isolates in 1983 were divided into three subtypes, which were associated with the cities isolated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoviridae↗
PubMed1986

Structural stability of heterologous genes cloned in Streptomyces plasmid pIJ702.

A recombinant plasmid pWCL1 containing Streptomyces plasmid pIJ702, E. coli plasmid pUC12, and hepatitis B viral surface antigen (HBsAg) gene was stably maintained in E. coli, but exhibited structural instability in S. lividans 1326. The deletions were found ranging from 2.75 to 5.65 kilobases (kb) and most of them occurred within the melanin (mel) gene of pIJ702, resulting in the loss of part of the mel gene sequence plus the insert. The removal of the pUC12 sequence from pWCL1 eliminated the instability. However, pUC12 alone inserted in either orientation on pIJ702 also caused the deletion in S. lividans 1326. The results indicated that the structural instability of hybrid plasmid of pIJ702 depended on the interaction between the mel sequence and the inserted sequence.

Chromosome Deletion↗
PubMed1986

Multistage model interpretation of additive and multiplicative carcinogenic effects.

Under the assumption of multistage carcinogenesis, a multiplicative carcinogenic effect would be produced by the action of different carcinogens in a mixture on different stages of the carcinogenic process. An additive effect would be produced by the effect of different carcinogens on the same stage. A mathematical argument for these hypotheses is presented here.

Carcinogens↗