A transformation-competent recombinant between v-src and Rous-associated virus RAV-1

Area of Science:

• Molecular Virology
• Retroviral Research
• Oncogenesis

Background:

• The H-19 hamster tumor harbors a unique provirus containing the viral src (v-src) oncogene flanked by long terminal repeats (LTRs).
• Understanding the rescue and genetic makeup of such oncogenic proviruses is crucial for deciphering viral oncogenesis and retroviral evolution.

Purpose of the Study:

• To rescue and characterize the LTR-v-src-LTR provirus from H-19 hamster tumor cells.
• To elucidate the recombination events and genetic alterations leading to the rescued virus's properties.

Main Methods:

• Cell fusion of H-19 cells with chicken fibroblasts infected with Rous-associated virus (RAV-1).
• Molecular analysis of the rescued viral genome, including nucleotide sequencing and identification of recombination sites.
• Assessment of RNA splicing and replication efficiency of the rescued virus.

Main Results:

• Successful rescue of the provirus by co-cultivation, yielding recombinant virus E6.
• E6 acquired approximately 1 kilobase of the 5' gag gene sequence from RAV-1.
• Recombination occurred within a 15-nucleotide homology region, altering the v-src splice acceptor site but preserving its functionality.
• The nucleotide structure suggests a dual reverse transcription jump mechanism for recombination.
• Acquisition of gag sequences conferred a replication advantage to E6 over the ancestral F6 virus.

Conclusions:

• The rescued E6 virus represents a novel recombinant with altered oncogene structure and enhanced replication.
• The study demonstrates a mechanism for proviral rescue and genetic reassortment involving template switching during reverse transcription.
• The findings provide insights into retroviral recombination, oncogene acquisition, and the evolution of replication-competent viruses from tumor cells.