Bap31 is a novel target of the human papillomavirus E5 protein

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Human papillomaviruses (HPVs) E5 oncoproteins are key viral factors, but their precise role in pathogenesis remains unclear.
• Understanding HPV E5 protein interactions is essential for elucidating viral mechanisms and developing targeted therapies.

Purpose of the Study:

• To identify novel binding partners of HPV E5 proteins.
• To investigate the functional significance of the HPV E5-Bap31 interaction in HPV pathogenesis.

Main Methods:

• Split-ubiquitin yeast two-hybrid system to screen for HPV E5 interacting proteins.
• Coimmunoprecipitation assays to confirm protein-protein interactions.
• Immunofluorescence microscopy to determine subcellular localization.
• Site-directed mutagenesis to identify critical domains for interaction.
• Small interfering RNA (siRNA) knockdown to assess protein function.

Main Results:

• B-cell-associated protein 31 (Bap31) was identified as a novel binding partner of HPV E5 proteins (HPV16 and HPV31).
• HPV E5 and Bap31 colocalize in the endoplasmic reticulum, suggesting a functional relationship within this organelle.
• Specific C-terminal amino acids of HPV E5 are critical for stabilizing the interaction with Bap31.
• Disruption of the E5-Bap31 interaction, either through E5 mutation or Bap31 knockdown, impairs the proliferative capacity of HPV-positive keratinocytes upon differentiation.

Conclusions:

• Bap31 is a novel binding partner of high-risk HPV E5 proteins.
• The interaction between HPV E5 and Bap31 plays a significant role in regulating the proliferation of HPV-infected keratinocytes during differentiation.
• These findings provide new insights into the molecular mechanisms underlying HPV pathogenesis and viral lifecycle modulation.