HPV16 E2 protein possesses intrinsic helicase activity and sterically hinders E1 function through direct interaction.

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Human papillomavirus type 16 (HPV16) E2 protein is crucial for viral replication.
• Previously, no enzymatic activity was attributed to the HPV16 E2 protein.

Purpose of the Study:

• To investigate the enzymatic activities of the HPV16 E2 protein.
• To identify potential antiviral targets and regulatory mechanisms in HPV replication.

Main Methods:

• Assessed ATP-dependent DNA unwinding activity of HPV16 E2.
• Performed mutational analysis to identify critical residues for helicase function.
• Investigated the interaction of podophyllotoxin with E2 and its effect on unwinding activity.
• Compared E2's helicase and ATPase activities with HPV16 E1.
• Examined the inhibitory effect of E2 on E1 helicase activity.

Main Results:

• HPV16 E2 protein possesses intrinsic ATP-dependent DNA unwinding (helicase) activity.
• Residues K299, Y303, and K306 are critical for E2's helicase function.
• Podophyllotoxin inhibits E2 unwinding activity (IC50 = 0.11±0.03 μM), involving residues Q320 and H342.
• E2's ATPase and helicase activities are weaker than E1's.
• E2 potently inhibits E1 helicase activity via its N-terminal domain (aa 1-245), involving residue E39.

Conclusions:

• The study uncovers a previously unrecognized helicase function for HPV16 E2 protein.
• E2 is a potential antiviral target due to its enzymatic activity.
• E2's inhibition of E1 reveals a novel regulatory mechanism in HPV DNA replication.