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Biomedical subjects

R D Wells

Publications and source records attributed to R D Wells.

At least 217 records · Page 12Linked to original sources
PubMed1973

RNA-DNA covalent bonds between the RNA primers and the DNA products formed by RNA tumor virus DNA polymerase.

Initiation of DNA synthesis by endogenous RNA primer molecules was studied with three different RNA tumor viruses. The influence of the method of virus disruption on the observed RNA-DNA bonds was ascertained. Ether disrupted virions of both murine leukemia virus (MuLV) and the B77 strain of avian sarcoma virus (B77 virus) have rC-dC and rA-dA covalent linkages between RNA primers and newly synthesized DNA. None of the 14 other possible bonds were formed. Ether-disrupted virions of avian myeloblastosis virus (AMV) have rU-dC and rA-dA linkages. In contrast, work reported herein and from other laboratories shows that Nonidet P-40 (NP-40)-disrupted virions of all three viruses have only the rA-dA junction. Studies with virus particles which were first disrupted with ether and then treated with NP-40 indicated that the detergent treatment disallowed the formation of the ribopyrimidine-dC internucleotide bond. The same transfers are found with AMV in the presence or absence of actinomycin D, where only single-stranded DNA is formed. This finding is consistent with the notion that virtually all of the significant primers have been recognized. In contrast to mature virions, transfer experiments with ether-disrupted early harvest (5 min) MuLV showed only the rC-dC bond; the rA-dA bond was absent. The short-time harvest contains a significantly higher proportion of infectious virions than 24-h harvests. Also, since the RNA from early harvest virus is appreciably more homogenous than the RNA of mature MuLV, it is concluded that the ribopyrimidine-dC linkage is the more significant initiation event from a biochemical standpoint.

Alpharetrovirus↗
PubMed1972

Lac repressor binding to synthetic DNAs of defined nucleotide sequence.

Binding of lac repressor to 20 synthetic DNAs of high molecular weight with defined repeating sequences was investigated by competition experiments. Although none of these DNAs binds repressor as tightly as does lac operator, most do bind to a measurable extent. Their affinity for repressor varies greatly and is a function of both nucleotide composition and sequence. Poly(dC-dC).poly(dG-dC) competes for repressor 200-times less well than either poly(dA-dT).poly(dA-dT) or poly(dT-dT-dG).poly(dC-dA-dA). The other DNAs show a broad spectrum of affinities for repressor between these extremes. These results show that the lac repressor has affinity for, and can distinguish between, sequences distantly related to its operator.

Base Sequence↗
PubMed1971

Nucleoside diphosphokinase activity associated with DNA polymerases.

Nucleoside diphosphokinase activity is present in highly purified preparations of DNA polymerase from Micrococcus luteus and Escherichia coli, and in a partially purified DNA polymerase from avian myeloblastosis virus. The activity is also observed in the protein fragment of molecular weight 76,000 that is produced by subtilisin cleavage of DNA polymerase I from E. coli. The NDP kinase activity in DNA polymerase preparations from M. luteus uses various ribo- and deoxyribonucleoside di- and triphosphates as substrates. The presence of this activity in preparations of DNA polymerase results in the apparent use of deoxyribonucleoside diphosphates as substrates for DNA synthesis, provided that some triphosphate is present to serve as a phosphate donor.

Adenosine Diphosphate↗