Project Details

Description

This laboratory has been interested in the effects of selenium compounds on
nucleic acid synthesis. We have carried out an investigation of the
effects of sodium selenite on DNA synthesis in 3 systems: intact cells,
isolated nuclei, and extracted polymerases. We found that in intact cells
as well as in isolated nuclei, selenite inhibits DNA synthesis
significantly. However, we also found that selenite was relatively
ineffective in inhibiting purified DNA polymerase, the enzyme which
catalyzes most of the synthesis in isolated nuclei. In more recent
experiments we have found that selenite can in fact inhibit DNA polymerase,
if a sulfhydryl compound such as mercaptoethanol is present in the
reaction. We have further found that other sulfhydryl compounds can have
the same potentiating effect on the inhibition of DNA polymerase by
selenite, although with varying potencies. We have also obtained evidence
for a similar effect with another enzyme, RNA polymerase II from wheat germ. The overall objective of the project is to characterize this phenomenon,
and to relate it to the inhibition by selenite of cellular DNA synthesis in
intact cells and isolated nuclei. In order to accomplish this we will
first characterize the specificity of the effect in terms of the SH
compound by carrying out a series of dose-response experiments to generate
a matrix of data on the effects of sodium selenite on DNA polymerase in the
presence of a series of SH compounds. This data will provide information
on the relative potencies of the various SH compounds and may provide
information on structure-function relationships. We will then examine the
specificity of the phenomenon in terms of the enzyme, by investigating the
ability of selenite to inhibit several other DNA and RNA polymerases, in
the presence of various SH compounds. From these results we will be able
to determine whether there are differences between the enzymes in the
relative potencies of the various SH compounds. We will investigate the
mechanism of the potentiation by exploring three models for the interaction
of SH compounds, selenite and the polymerase. We will also attempt to
determine whether the inhibitory effect of selenite on DNA synthesis in
isolated nuclei results from SH-potentiated inhibition of the DNA
polymerase by selenite, by investigating the effect of adding SH compounds
to the nuclei reactions, or depleting the nuclei of possible endogenous SH
compounds.Description
StatusFinished
Effective start/end date6/15/863/31/99

Funding

  • National Institutes of Health: $203,020.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $190,638.00
  • National Institutes of Health: $160,266.00
  • National Institutes of Health: $150,058.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health

ASJC

  • Environmental Science(all)
  • Medicine(all)

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