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L F Cavalieri

Publications and source records attributed to L F Cavalieri.

7 recordsLinked to original sources
PubMed1978

Effects of benzo(a)pyrene adducts of DNA synthesis in vitro.

Two diol epoxides of benzo(a)pyrene (BP), and benzo(a)pyrene 4,5-oxide, have been used to make adducts in the homopolymers polyribocytidylic acid, (rC); polyriboadenylic acid (rA), polydeoxycytidylic acid (dC) and polydeoxyadenylic acid (dA). With appropriate oligomers as primers these modified and unmodified polynucleotides were used as templates for DNA synthesis with avian myeloblastosis virus DNA polymerase (AMV) or E. coli Pol I DNA polymerase. We have found that: (1) the size of the DNA product is not markedly decreased by the presence of these these polycyclic aromatic hydrocarbon adducts in the templates; (2) the presence of adducts does not lead to increased incorporation of erroneous bases. These results, supported by kinetic data, suggest that these polymerases can bypass a site containing an adduct on the template without leaving a gap or causing misincorporation of a base and they imply that mutagenesis by BP may not be attributable to either of these mechanisms.

Avian Myeloblastosis Virus↗
PubMed1978

Inhibition of reverse transcription of 70S and 35S avian myeloblastosis RNAs by nonprimer tRNA's.

We studied the kinetics of the reverse transcription of 70S and 35S RNA of avian myeloblastosis virus in the presence and absence of various tRNA's. All tRNA's inhibited synthesis. tRNA's from Escherichia coli and yeast exhibited a noncompetitive type of inhibition, i.e., they bound reversibly and randomly and did not alter the affinity of the viral RNA for the polymerase. Nonprimer tRNA's obtained from 70S RNA molecules produced a complex pattern of inhibition. The results show that the nonprimer tRNA's which bound to the reverse transcriptase decreased the affinity of the viral RNA for the enzyme. The maximum rate of synthesis with 70S RNA as the template was less than that with 35S RNA, presumably because the former contains nonprimer tRNA's which can interact with the polymerase.

Avian Leukosis Virus↗
PubMed1977

Characterization of a DNA polymerase associated with an endogenous DNA-synthesizing complex isolated from human lymphoid cells.

We have shown that a membrane fraction prepared from isolated human lymphoid nuclei contains endogenous DNA-synthesizing activity which is sensitive to RNAase. We have isolated a DNA polymerase from this fraction and partially purified it to what we estimate as about 10 000-fold. Its chromatographic behavior, template specificity, sedimentation constant, pH optimum, and sensitivity to N-ethylmaleimide suggest that the activity resembles but is not identical to DNA polymerase gamma (formerly called R-DNA polymerase). The membrane fraction also contains a minor activity which is due to polymerase beta, the low molecular weight (3.5 S) nuclear enzyme.

Cell Line↗
PubMed1976

Mechanism of interaction of avian myeloblastosis virus reverse transcriptase with avian myeloblastosis virus RNA.

The synthesis of DNA on avian myeloblastosis virus (AMV) RNA as the primer-template using AMV reverse transcriptase in vitro has been examined as a function of the concentrations of these components, as well as a function of the ionic strenth of the assay medium. The results are consistent with the hypothesis that two types of sites exist on the AMV RNA: inactive "dead-end" sites that merely bind the enzyme, and active binding sites that lead to DNA synthesis. Velocity sedimentation studies of reverse transcriptase reveal that the enzyme becomes a dimer (or oligomer) at low salt concentrations and it is at these concentrations that the two types of sites are evident on the RNA. At high salt concentration the enzyme, which exists primarily as a monomer, is inactive with AMV RNA, although it is active when poly(rA)dT10 is used as the primer-template. We have shown that inactive sites are not due to binding of the reverse transcriptase to nicked regions or to partially denatured RNA molecules. We deduce that inactive sites are those containing incorrect 4S primer molecules. These results are discussed in terms of the mechanism of the interaction of the reverse transcriptase with AMV RNA.

Avian Leukosis Virus↗
PubMed1975

E. coli tRNAs as inhibitors of viral reverse transcription in vitro.

Reverse transcription of 70S AMV RNA by AMV reverse transcriptase has been studied in the presence of E. coli tRNAs. We have shown that inhibition of DNA synthesis occurs and that the tRNAs bind to the enzyme and not to the 70S RNA. The results have implications for the control of reverse transcription in vivo.

Avian Myeloblastosis Virus↗
PubMed1975

In vitro DNA synthesis on smooth membranes observed by fluorescence.

Smooth membranes have been isolated from a human diploid line of lymphocytes. These membranes exhibit an endogenous DNA-synthesizing capability which is partially destroyed by prior treatment with RNase. In order to ascertain the role of the membranes in the DNA synthesis we have examined the conformation of the membrane proteins by observing fluorescence changes of the intrinsic probe, tryptophan. We have observed that on addition of the deoxynucleoside-5'-triphosphates, which permits DNA synthesis, there are fluorescence changes due to the tryptophan residue; when DNA synthesis is prevented by omitting some of the precursor triphosphates, fluorescence changes are absent. These effects have been observed with plasma and nuclear membrane fractions; the former may contain a small fraction of the latter. Similar membrane preparations from non-lymphoid cells do not process the endogenous DNA-synthesizing system, as shown by the lack of incorporation of radioactive precursors of fluorescence changes.

Cell Line↗