Temporal mapping of transcripts in human herpesvirus-7.

Area of Science:

• Virology
• Molecular Biology

Background:

• Human herpesvirus-7 (HHV-7) is a common human virus.
• Understanding HHV-7 transcription is crucial for comprehending its replication cycle and pathogenesis.

Purpose of the Study:

• To investigate the temporal regulation of human herpesvirus-7 (HHV-7) gene transcription in productively infected T-cells.
• To elucidate the mechanisms of viral gene expression, including the roles of alpha, beta, and gamma genes and splice mechanisms.

Main Methods:

• Studied HHV-7 transcription in productively infected T-cell cultures.
• Utilized cycloheximide and phosphonoacetate to differentiate gene expression kinetics.
• Analyzed pre-mRNA and spliced transcript detection to determine gene function and temporal regulation.

Main Results:

• HHV-7 transcription follows a herpesvirus cascade: alpha, beta, and gamma genes are sequentially transcribed.
• Alpha genes (e.g., U10, U89/90) were detected early and independent of protein synthesis.
• Beta genes (e.g., U19) required protein synthesis, while gamma genes (e.g., U60/66) showed late-phase spliced transcript production. Splice mechanisms were also temporally regulated.
• Viral transcripts were not detected in peripheral blood mononuclear cells of healthy HHV-7 infected donors, indicating latent infection.

Conclusions:

• HHV-7 gene expression is regulated by complex, coordinated activation of viral promoters and post-transcriptional processing.
• Splice mechanisms are temporally regulated, with some transcripts showing immediate-early or late-phase processing.
• HHV-7 establishes latent infections in the adult population.