Epstein-Barr virus BNRF1 destabilizes SMC5/6 cohesin complexes to evade its restriction of replication compartments. Yiu et al.

Delivery of ~170 kilobase EBV genomes to nuclei, and use of nuclear membrane-less replication compartments (RC) for their lytic cycle amplification, necessitate evasion of intrinsic antiviral responses. Proteomic analysis identified that upon B-cell infection or lytic reactivation, EBV depletes the chromosome maintenance cohesin SMC5/6, which has major chromosome maintenance roles and DNA damage repair.

The major tegument protein BNRF1 targeted SMC5/6 complexes by a ubiquitin proteasome pathway dependent on calpain proteolysis and cullin-7. In the absence of BNRF1, SMC5/6 associated with R-loop structures, including at the viral lytic origin of replication, and interfered with RC formation and encapsidation. CRISPR analysis highlighted RC restriction roles of SMC5/6 components involved in DNA entrapment and SUMOylation.