Surfeit 4 Contributes to the Replication of Hepatitis C Virus Using Double-Membrane Vesicles

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Positive-strand RNA viruses like HCV and poliovirus replicate within double-membrane vesicles (DMVs).
• The precise role of host proteins in DMV formation during viral replication remains largely unknown.
• Hepatitis C virus NS4B protein induces a membranous web structure crucial for viral replication complex assembly.

Purpose of the Study:

• To investigate the role of the cellular protein Surfeit 4 (Surf4) in hepatitis C virus (HCV) replication.
• To elucidate the mechanism by which Surf4 influences viral replication and double-membrane vesicle (DMV) formation.
• To determine if Surf4's role extends to other positive-strand RNA viruses utilizing DMVs.

Main Methods:

• Dual-affinity purification coupled with LC-MS/MS to identify host proteins associated with HCV NS4B.
• Small interfering RNA (siRNA) screening to assess the impact of host genes on viral replication.
• Analysis of viral replication in the presence and absence of Surf4, including genotype-independent assays.
• Investigating Surf4's recruitment into replication complexes and its effect on DMV formation and other viral life cycle stages.

Main Results:

• Surf4 is recruited into HCV RNA replication complexes by NS4B and is critical for DMV formation and replication complex integrity.
• Surf4 influences HCV replication in a genotype-independent manner, without affecting viral entry, translation, assembly, or release.
• Surf4 also supports poliovirus replication, which uses DMVs, but not dengue virus replication, which uses different vesicle types.
• HCV replication does not alter Surf4 expression levels.

Conclusions:

• Surf4 is a novel host cofactor essential for the replication of positive-strand RNA viruses that depend on double-membrane vesicles (DMVs).
• Surf4's function in DMV formation provides crucial insights into viral replication strategies and potential therapeutic targets.
• The findings highlight Surf4's specific role in DMV-dependent viral replication, distinguishing it from viruses using other vesicle structures.