Related Experiment Videos
Characterization and separation of viral DNA polymerase in mouse milk
Abstract:
Two DNA polymerase with properties of viral RNA-directed DNA polymerase can be found in RIII mouse milk. One enzyme is the polymerase of type-C viruses; this enzyme prefers manganese to magnesium with poly(rA).oligo(dT) as synthetic template, is inhibited by specific sera, and has an apparent molecular weight of 70,000. Milk from BALB/c and NIH Swiss mice contain a vast predominance of this type-C enzyme. The other DNA polymerase from RIII mouse milk prefers magnesium to manganese, is not inhibited by type-C antipolymerase serum, and appears larger on gel chromatography than the type-C viral polymerase. Its presence in milk from RIII mice and absence from milk of mice with low content of mammary tumor virus correlates to the relative degree of type-B virus expression in these mice. The DNA polymerase of Mason-Pfizer monkey virus, isolated from a rhesus monkey breast tumor, also has a marked preference for magnesium with poly(rA).oligo(dT), is not immunologically related to primate type-C viruses, and appears larger than the gibbon type-C enzyme on gel chromatography.
Insights
RIII mouse milk contains two RNA-directed DNA polymerases. One is a type-C viral enzyme, while the other, associated with mammary tumor virus, prefers magnesium and is immunologically distinct.
Area of Science:
- Biochemistry
- Virology
- Molecular Biology
Background:
- Mouse milk contains viral RNA-directed DNA polymerases.
- These enzymes are associated with retroviruses, including mammary tumor virus (MTV).
Purpose of the Study:
- To characterize the DNA polymerases found in RIII mouse milk.
- To differentiate these enzymes based on their biochemical and immunological properties.
- To correlate enzyme presence with viral expression in different mouse strains.
Main Methods:
- Enzyme assays using synthetic templates (poly(rA).oligo(dT)) to determine cofactor preferences (magnesium vs. manganese).
- Inhibition assays using specific antisera against type-C viral polymerase.
- Gel chromatography to estimate molecular weights.
- Comparison with Mason-Pfizer monkey virus DNA polymerase.
Main Results:
- RIII mouse milk contains two distinct DNA polymerases.
- One enzyme is identified as a type-C viral polymerase, preferring manganese and inhibited by specific sera.
- The second enzyme prefers magnesium, is not inhibited by type-C antisera, and appears larger; its presence correlates with type-B virus (MTV) expression.
- Mason-Pfizer monkey virus DNA polymerase shares magnesium preference and size characteristics with the second RIII mouse milk enzyme.
Conclusions:
- RIII mouse milk harbors at least two distinct RNA-directed DNA polymerases.
- One enzyme is associated with type-C viruses, while the other is likely related to mammary tumor virus.
- The findings highlight differences in viral DNA polymerases and their association with specific viruses in mice and primates.