Satellite Subgenomic Particles Are Key Regulators of Adeno-Associated Virus Life Cycle

Historically, adeno-associated virus (AAV)-defective interfering particles (DI) were known as abnormal virions arising from natural replication and encapsidation errors. Through single virion genome analysis, we revealed that a major category of DI particles contains a double-stranded DNA genome in a snapback configuration. The 5 '- snapback genomes (SBGs) include the P5 promoters and partial rep gene sequences. The 3 '-SBGs contains the capsid region. The molecular configuration of 5 '-SBGs theoretically may allow double-stranded RNA transcription in their dimer configuration. Our studies demonstrated that 5-SBG regulated AAV rep expression and improved AAV packaging. In contrast, 3 '-SBGs at its dimer configuration increased levels of cap protein. The generation and accumulation of 5 '-SBGs and 3 '-SBGs appears to be coordinated to balance the viral gene expression level. Therefore, the functions of 5 '-SBGs and 3 '-SBGs may help maximize the yield of AAV progenies. We postulate that AAV virus population behaved as a colony and utilizes its subgenomic particles to overcome the size limit of a viral genome and encodes additional essential functions.

Automated summary

Historically, adeno-associated virus (AAV) defective interfering particles (DI) were considered abnormal virions resulting from replication and encapsidation errors. Through single virion genome analysis, it was revealed that a major category of DI particles contain double-stranded DNA genomes in snapback configuration. The 5'-SBGs and 3'-SBGs have different functions in regulating AAV gene expression levels in their dimer configurations.