Bromodomain protein 4 mediates the papillomavirus E2 transcriptional activation function

Area of Science:

• Molecular Virology
• Cell Biology
• Epigenetics

Background:

• The papillomavirus E2 protein regulates viral transcription, DNA replication, and genome maintenance.
• Brd4 is a known E2-interacting protein, crucial for tethering viral genomes to mitotic chromosomes for maintenance.
• The full scope of Brd4's involvement in E2 functions beyond chromosomal tethering is not well understood.

Purpose of the Study:

• To investigate the role of Brd4 in other essential functions of the papillomavirus E2 protein.
• To determine if Brd4 influences E2-mediated viral transcription and DNA replication.

Main Methods:

• Alanine-scanning substitution mutagenesis of the human papillomavirus type 16 E2 N-terminal transactivation domain.
• Analysis of Brd4 binding to E2 mutants.
• Functional studies using Brd4 C-terminal domain competition and short interfering RNA (siRNA) knockdown of Brd4.

Main Results:

• Specific amino acids in the E2 N-terminal domain are critical for both Brd4 binding and transcriptional activation.
• These critical amino acids are not required for E2's viral DNA replication function.
• Functional studies confirmed Brd4's role in E2-mediated transcriptional activation, but not in viral DNA replication.

Conclusions:

• Brd4 plays a significant role in papillomavirus transcriptional regulation via interaction with the E2 protein.
• Brd4's function extends beyond mitotic chromosome tethering, impacting the broader papillomavirus life cycle.
• These findings highlight Brd4 as a key regulator in papillomavirus replication and pathogenesis.