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Biomedical subjects

J C Yin

Publications and source records attributed to J C Yin.

8 recordsLinked to original sources
PubMed1988

Effect of dam methylation on Tn5 transposition.

The effect of dam methylation on Tn5 transposition was investigated by analyses of mutations in the host (Escherichia coli) and the element. Wild-type elements transposed at a higher frequency and showed higher levels of transposase expression in a dam-host. Mutations were made in the promoter region of the transcript that codes for the transposase. Transposition and transposase levels from these mutants were independent of the host methylation system. Measurements of the amount of RNA support the hypothesis that dam methylation exerts its effect on Tn5 transposition by modulating the frequency of transcriptional initiation of the transposase gene. Since Tn5 transposition increases when the transposase levels increase, at normal concentrations the amount of transposase is a rate-limiting factor that determines the transposition frequency of Tn5. Transposition of IS50, one of the insertion sequences that constitutes Tn5, is also sensitive to dam methylation by a second mechanism in addition to that of modulating transcriptional initiation. dam methylation, either directly or indirectly, inhibits the usage of IS50 sequences by the transposase. Thus, dam methylation can affect both the expression of the transposase and the DNA substrate upon which it acts.

DNA Transposable Elements↗
PubMed1988

p2 and inhibition of Tn5 transposition.

Mutations of Tn5 which decreased the amount of the shorter element-encoded protein (p2) were made. One mutation was a change in the translation initiation codon of the protein, while two other mutations were changes in the promoter of the transcript (T2) which codes for p2. Analysis of all three mutants indicates that they decreased the inhibition of transposition that the protein exerts (in trans) on another element. The mutants have complicated transposition behaviors. Analysis of the RNA and proteins synthesized from the mutants led to the proposal that p2 can inhibit transposition at normal physiological concentrations. Therefore p2 synthesized from a given element is partly responsible for controlling the transposition frequency of the element. The mutants also show that p1 is the only Tn5-encoded protein necessary for transposition.

Bacterial Proteins↗
PubMed1987

dnaA, an essential host gene, and Tn5 transposition.

Mutations in dnaA, an essential gene in Escherichia coli, decrease the frequency of transposition of Tn5. An insertion mutation in the dnaA gene does not affect Tn5 gene expression. Therefore, the DnaA protein plays a role either in the transposition reaction itself or in some type of cellular regulation of transposition. Analysis of a mutation in the DnaA box, found at the outside end of IS50, is consistent with a direct interaction of the protein through these bases. IS50 transposition, which utilizes only one end containing a DnaA box, is not affected by dnaA mutations. Overproduction of the DnaA protein does not increase transposition frequencies in wild-type cells, even when the transposase is also overproduced.

Bacterial Proteins↗
PubMed1976

[Vitamin C].

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Ascorbic Acid↗