Electron microscopy of the nucleic acid of mouse mammary tumor virus
Abstract:
Mouse mammary tumor virus (MTV) was isolated from the milk of RIII mice by density-gradient centrifugation in Ficoll. The homogeneity of the preparation was demonstrated in electron micrographs. The nucleic acid was extracted with phenol in the presence of Pronase. Its viral origin was attested by failure of ribo-nuclease and deoxyribonuclease treatment of the virus preparation to destroy the filamentous molecules; after phenol extraction, the molecules were destroyed by ribonuclease but not by deoxyribonuclease. Rotary shadowed preparations were examined in the electron microscope. The length distribution of the RNA filaments showed peaks at 1.2, 2.4, and 3.6 mum. The molecular weight of the longest molecule of MTV-RNA was estimated as 3.6 x 10(6) daltons.
Insights
Researchers isolated Mouse Mammary Tumor Virus (MTV) from RIII mouse milk. Analysis revealed MTV RNA filaments with lengths up to 3.6 micrometers and a molecular weight of 3.6 x 10^6 daltons.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Mouse Mammary Tumor Virus (MTV) is a retrovirus associated with mammary tumors in mice.
- Understanding the physical and biochemical properties of MTV is crucial for studying its oncogenic potential.
Purpose of the Study:
- To isolate and characterize the RNA genome of Mouse Mammary Tumor Virus (MTV).
- To determine the physical dimensions and molecular weight of MTV RNA.
Main Methods:
- MTV was isolated from RIII mouse milk using Ficoll density-gradient centrifugation.
- Viral RNA was extracted using phenol and Pronase.
- RNA integrity and origin were assessed using RNase and DNase treatments.
- RNA filament lengths were measured by electron microscopy of rotary-shadowed preparations.
- Molecular weight was estimated based on RNA filament length.
Main Results:
- Homogeneous MTV preparations were obtained.
- Extracted RNA molecules were sensitive to RNase but resistant to DNase, confirming their viral RNA nature.
- Electron microscopy revealed MTV RNA filaments with length peaks at 1.2, 2.4, and 3.6 µm.
- The longest MTV RNA molecule was estimated to have a molecular weight of 3.6 x 10^6 daltons.
Conclusions:
- The study successfully isolated and characterized the RNA genome of MTV.
- MTV possesses a large, single-stranded RNA genome with distinct size distributions.
- These findings provide fundamental data on the molecular composition of MTV, relevant for further oncogenesis research.
