Immunological characterization of the low-molecular-weight DNA binding protein of mouse mammary tumor virus
Abstract:
p14, a low-molecular-weight MMTV protein previously identified as having DNA-binding properties and encoded by the gag region of the MMTV genome, was purified by affinity chromatography on DNA-sepharose. Immunological characterization of the purified protein showed that MMTV p14 shares no cross-reactivity with gp52, gp36 and p10, antigens associated with the MMTV envelope, nor with p27 antigen found in the virion core. Purified MMTV p14 did show cross-reactivity with purified intracytoplasmic A particles, supporting the concept that A particles are morphological precursors to MMTV cores. In addition, shared antigenic determinants between intracytoplasmic A particles and MMTV p27, p20 and p10 were demonstrated. MMTV p14 did not cross-react with the low-molecular-weight DNA-binding proteins of MuLV or of type-C or -D viruses of higher mammals.
Insights
Researchers purified a mouse mammary tumor virus (MMTV) protein, p14, which binds DNA. This MMTV p14 protein is antigenically related to intracytoplasmic A particles, suggesting they are precursors to MMTV cores.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- The mouse mammary tumor virus (MMTV) is a retrovirus associated with mammary tumors in mice.
- MMTV encodes various proteins, including p14, a low-molecular-weight protein with DNA-binding properties.
- Understanding the antigenic relationships of viral proteins is crucial for characterizing viral structure and replication.
Purpose of the Study:
- To purify and immunologically characterize the MMTV p14 protein.
- To investigate the antigenic relationship between MMTV p14 and other MMTV components.
- To explore the potential role of MMTV p14 in the viral life cycle and its relation to intracytoplasmic A particles.
Main Methods:
- Affinity chromatography using DNA-sepharose for p14 purification.
- Immunological characterization using cross-reactivity assays.
- Comparison with antigens from MMTV envelope, virion core, intracytoplasmic A particles, and other retroviruses.
Main Results:
- MMTV p14 was successfully purified, confirming its DNA-binding ability.
- MMTV p14 showed no cross-reactivity with MMTV envelope antigens (gp52, gp36, p10) or virion core antigen (p27).
- Purified MMTV p14 exhibited cross-reactivity with intracytoplasmic A particles, supporting their role as MMTV core precursors. Shared determinants were also found between A particles and MMTV p27, p20, and p10.
- MMTV p14 did not cross-react with DNA-binding proteins from MuLV or other mammalian retroviruses.
Conclusions:
- MMTV p14 is antigenically distinct from MMTV envelope and core proteins but shares determinants with intracytoplasmic A particles.
- These findings support the hypothesis that intracytoplasmic A particles are precursors to MMTV cores.
- MMTV p14 represents a unique viral protein with specific antigenic properties relevant to MMTV morphogenesis.
