TRIM5α requires Ube2W to anchor Lys63-linked ubiquitin chains and restrict reverse transcription

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• TRIM5α is a cytoplasmic E3 ubiquitin ligase that restricts retroviral infection by targeting viral capsids.
• It inhibits viral reverse transcription and can stimulate innate immunity via polyubiquitin chain synthesis.

Purpose of the Study:

• To elucidate the mechanism by which TRIM5α synthesizes anchored polyubiquitin chains.
• To identify the specific E2 ubiquitin-conjugating enzymes involved in TRIM5α auto-ubiquitination and restriction.

Main Methods:

• In vitro and in-cell experiments using TRIM5α and various E2 enzymes (Ube2W, Ube2N/Ube2V2).
• Analysis of TRIM5α ubiquitination sites, including specific lysine residues (K45, K50).
• Assessment of viral reverse transcription and infection upon E2 enzyme depletion or ubiquitin mutation.

Main Results:

• TRIM5α utilizes Ube2W to initiate auto-ubiquitination via monoubiquitination of internal lysines (K45, K50).
• This monoubiquitination serves as a substrate for Ube2N/Ube2V2 to elongate Lys63-linked polyubiquitin chains.
• Depletion of E2 enzymes or mutation of ubiquitin impaired TRIM5α ubiquitination and restored viral reverse transcription.

Conclusions:

• Stepwise formation of anchored Lys63-linked polyubiquitin chains is critical for TRIM5α's antiviral restriction mechanism.
• Ube2W and the Ube2N/Ube2V2 complex are key E2 cofactors in TRIM5α auto-ubiquitination and function.