Search PubMed⌕ Search

Biomedical subjects

R Wu

Publications and source records attributed to R Wu.

At least 469 records · Page 26Linked to original sources
PubMed1978

Physical mapping of BK virus DNA with SacI, MboII, and AluI restriction endonucleases.

A new restriction endonuclease, SacI from Streptomyces achromogenes cleaves BK virus (strain MM) DNA into 3 fragments, whereas MboII from Moraxella bovis and AluI from Arthrobacter luteus give 22 and 30 fragments, respectively. All these specific DNA fragments were ordered and mapped on the viral genome by two methods first, by the reciprocal digestion method using uniformly 32P-labeled DNA; and second, by the partial digestion technique using the single-end 32P-labeled DNA. This study, together with those reported earlier, defined the location of 90 cleavage sites on the BK virus DNA.

BK Virus↗
PubMed1977

Novel properties of Escherichia coli exonuclease III.

The specificity of hydrolysis of polynucleotide termini by Escherichia coli exonuclease III was studied with the use of oligothymidylate annealed to polydeoxyadenylate. The size of the products after 3' leads to 5'-hydrolysis of 5'-labeled substrate is temperature-dependent. At 25 degrees the enzyme can hydrolyze a polynucleotide chain up to the last 5'-terminal dinucleotide. A gradation of higher 5'-terminal oligonucleotides of defined chain lengths is produced after limit digestion by the enzyme when the temperature is raised between 25 degrees to 60 degrees. When the oligothymidylate was labeled at the 3'-ends with ribonucleotides, it was observed that exonuclease III can cleave a single or two consecutive ribonucleotides regardless of whether the ribonucleotides are base-paired or mismatched.

Deoxyribonucleases↗
PubMed1977

Minimal length of the lactose operator sequence for the specific recognition by the lactose repressor.

A number of specific duplex DNA sequences which correspond to varying lengths of the lactose operator region have been synthesized by a combination of chemical and enzymatic methods. Repressor binding studies on these synthetic duplex operator molecules show that all the nucleotides essential for full lactose operator-repressor interactions are included in a 17-nucleotide-long duplex DNA that constitutes the minimal recognition sequence for this DNA-protein interaction.

Base Sequence↗
PubMed1977

Arylsulfonyltetrazoles, new coupling reagents and further improvements in the triester method for the synthesis of deoxyribooligonucleotides.

The modified triester approach has been further improved and refined to the synthesis of defined sequences of deoxyribo-oligonucleotides. Improvements include arylsulfonyltetrazoles as faster and milder condensing agents, benzenesulfonic acid to avoid depurination during deblocking of trityl protecting groups and improved chromatographic procedures for purification of triester intermediates and purification of the final product containing 3'-5' phosphodiester linkages.

DNA Restriction Enzymes↗
PubMed1977

Relaxed circular SV40 DNA as cleavage intermediate of two restriction endonucleases.

We have determined the mode of cleavage of superhelical SV40 DNA (Form I) by restriction endonucleases EcoRI and HpaII at 37 degrees C. By analysis with agarose gel electrophoresis and direct examination with dark field electron microscopy, we found that a large amount of the single-nicked circular DNA (Form II) was produced before the linear SV40 DNA (Form III) appeared. Thus, both restriction enzymes cleave only one strand of the superhelical DNA first. The second cleavage on the complementary strand occurred after a lag period. The first order rate constant for the second cleavage by EcoRI endonuclease was determined and a kinetic reaction scheme for both enzymes is proposed.

DNA Restriction Enzymes↗
PubMed1977

Distinctive protein requirements of replication-dependent and -uncoupled bacteriophage T4 late gene expression.

This paper further explores the relationship of viral DNA replication to bacteriophage T4 late gene expression. It is shown that replication coupled and -independent late transcription make different qualitative or quantitative demands on phage protein synthesis. In further analysis of these different protein synthesis requirements, experiments were performed with a temperature-sensitive mutant in T4 gene 55 (ts553). It is known that the gene 55 product regulates T4 late gene expression and binds to RNA polymerase. In the experiments presented here, it is shown that the temperature sensitivity of the ts553 gene 55 protein depends on whether it is involved in replication-coupled or -independent T4 late transcription. This is evidence that the proteins constituting the transcription apparatus interact differently with late transcription units in T4 DNA, depending on whether late transcription is replication coupled or independent.

Chloramphenicol↗
PubMed1976

Cloned synthetic lac operator DNA is biologically active.

A chemically synthesised duplex DNA fragment containing the sequence of the lac operator was cloned in E. coli using the vehicle pMB9. Clones containing lac-pMB9 hybrid DNA produced beta-galactosidase constitutively and the hybrid DNA bound the lac repressor specifically.

Bacterial Proteins↗
PubMed1976

Arthrobacter luteus restriction endonuclease recognition sequence and its cleavage map of SV40 DNA.

The nucleotide sequence at the cleavage site of the restriction endonuclease isolated from Arthrobacter luteus (Alu) has been determined. The endonuclease cleaves at the center of a palindromic tetranucleotide sequence to give even-ended duplex DNA fragments phosphorylated at the 5'-end. The endonuclease cleaves SV40 form I DNA into 32 fragments. The order and sizes of these fragments have been determined to provide an Alu cleavage map of the SV40 genome.

Arthrobacter↗
PubMed1976

Synchronous digestion of SV40 DNA by exonuclease III.

We have established an optimal condition for the synchronous digestion of SV40 DNA with Escherichia coli exonuclease III. Electron microscopy and polyacrylamide gel electrophoresis were used to obtain accurate measurements on the lengths of DNA before and after exonuclease III digestion. Based on this finding, a new method for determining the sequence of long duplex DNA can be realized. It involves (a) the synchronous digestion of the DNA from the 3' ends with exonuclease III, followed by (b) repair synthesis with labeled nucleotides and DNA polymerase, and (c) sequence analysis of the repaired DNA.

Base Sequence↗