Expression of mouse mammary tumor viral polypeptides in milks and tissues
Abstract:
A 14,000-dalton polypeptide (p14) from RIII murine mammary tumor virus (MMTV) has been isolated by column chromatography in 6 M GuHCl. Antiserum prepared in rabbits specifically precipitated 125I-labeled p14; in double antibody competition, radioimmunoassays performed with limiting amounts of antibody, both purified p14 and disrupted MMTV, competed specifically with labeled antigen. The expression of this MMTV type B virus antigen could be measured by competition radioimmunoassays in milks, mammary glands, tumors, and tissue culture cells. MMTV expression measured by p14 immunoassay correlated well with the spontaneous incidence of mammary adenocarcinomas in different murine strains but not with type C MuLV p30 antigen expression. Levels of MMTV gp52, the major type-B viral glycoprotein, corresponded to p14 levels, suggesting that their control is comparably regulated. Evidence that this low m.w. polypeptide is present in feral and inbred strains of widely differing geographic origin and in MMTV with apparently different biologic properties suggests surprising conservation of MMTV protein homology.
Insights
Researchers isolated a 14,000-dalton polypeptide (p14) from murine mammary tumor virus (MMTV). This MMTV antigen expression correlates with mammary cancer incidence in mice, indicating its significance.
Area of Science:
- Virology
- Oncology
- Immunology
Background:
- Murine mammary tumor virus (MMTV) is associated with mammary adenocarcinoma development in mice.
- Understanding MMTV protein expression is crucial for studying viral pathogenesis and cancer.
- Previous studies focused on major viral glycoproteins, leaving smaller polypeptides less characterized.
Purpose of the Study:
- To isolate and characterize a low-molecular-weight polypeptide (p14) from MMTV.
- To develop a radioimmunoassay for measuring MMTV p14 expression.
- To correlate MMTV p14 expression with mammary tumor incidence and other viral antigens.
Main Methods:
- Isolation of MMTV p14 using column chromatography in 6 M GuHCl.
- Development of specific antiserum against MMTV p14 in rabbits.
- Quantification of MMTV p14 expression using competition radioimmunoassays in various mouse tissues and cell cultures.
Main Results:
- A 14,000-dalton polypeptide (p14) was successfully isolated from MMTV.
- MMTV p14 expression, measured by radioimmunoassay, correlated significantly with the spontaneous incidence of mammary adenocarcinomas across different mouse strains.
- MMTV p14 levels paralleled the expression of MMTV gp52, the major viral glycoprotein, suggesting coordinated regulation.
- MMTV p14 showed conserved homology across geographically diverse MMTV strains.
Conclusions:
- MMTV p14 is a conserved viral protein whose expression is linked to mammary tumor development.
- The p14 immunoassay provides a valuable tool for assessing MMTV expression and its oncogenic potential.
- The findings highlight the importance of low-molecular-weight viral proteins in MMTV pathogenesis and suggest conserved regulatory mechanisms.
