Characterization of DNA polymerase and RNA associated with A-type particles from murine myeloma cells

Area of Science:

• Molecular Biology
• Virology
• Oncology

Background:

• Intracisternal A-type particles (A-particles) are retrovirus-like elements found in mouse myeloma cells.
• Their biological significance and relationship to other retroviruses remain incompletely understood.

Purpose of the Study:

• To investigate the enzymatic activity of RNA-dependent DNA polymerase within A-particles.
• To characterize the template specificity and product of this polymerase.
• To explore potential viral associations of A-particles.

Main Methods:

• Purification of intracisternal A-type particles from mouse myeloma tumor cells.
• Assay of RNA-dependent DNA polymerase activity using endogenous A-particle RNA and synthetic polynucleotides (poly [rA]) as templates.
• Analysis of the size and hybridization properties of the synthesized DNA products.
• Characterization of RNA components within purified A-particles.

Main Results:

• A-particles possess RNA-dependent DNA polymerase activity.
• The polymerase utilizes both endogenous A-particle RNA and exogenous poly (rA) templates.
• The DNA product is small (4S-10S) and hybridizes extensively to A-particle RNA (>90%).
• A significant portion of the DNA product also hybridizes to murine sarcoma-leukemia virus RNAs (up to 50%).
• A-particle RNA consists mainly of low molecular weight species (5S-15S) with minor 70S and 35S components.

Conclusions:

• The presence and activity of RNA-dependent DNA polymerase in A-particles indicate potential retroviral characteristics.
• The hybridization data suggest a molecular relationship between A-particles and C-type oncornaviruses.
• A-type particles may represent a distinct but related family of retroviral elements.