Nucleocytoplasmic shuttling of the human parainfluenza virus type 2 phosphoprotein

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Human parainfluenza virus type 2 phosphoprotein (P) is vital for viral polymerase function.
• The P gene also produces the accessory V protein through gene editing, sharing N-terminal amino acids with P.
• P protein typically resides in the cytoplasm, whereas V protein is primarily nuclear.

Purpose of the Study:

• To investigate the nucleocytoplasmic localization signals of human parainfluenza virus type 2 P protein.
• To determine the functional significance of P protein's nucleocytoplasmic shuttling in viral activity.

Main Methods:

• Deletion mutants were used to identify nuclear localization signal (NLS) and nuclear export signal (NES) regions.
• Complex formation with importin α5 or 7 was analyzed.
• Leptomycin B treatment was employed to assess CRM1-dependent NES activity.
• β-galactosidase fusion proteins were utilized to pinpoint specific NLS and NES sequences.

Main Results:

• An NLS was identified in the common P/V domain, and a CRM1-dependent NES was found in the P-specific C-terminal region.
• The NLS sequence was determined as ⁶⁵PVKPRRKK⁷², and the NES sequence as ²²⁵IIELLKGLDL²³⁴.
• P protein forms complexes with importin α5 or 7 via its NLS.
• Leptomycin B treatment caused P protein nuclear retention, confirming the NES function.

Conclusions:

• Human parainfluenza virus type 2 P protein possesses both NLS and NES, enabling nucleocytoplasmic shuttling.
• The identified NLS (⁶⁵PVKPRRKK⁷²) and NES (²²⁵IIELLKGLDL²³⁴) mediate P protein's transport.
• Nucleocytoplasmic shuttling of P protein is essential for efficient viral polymerase activity.