Abstract
Host shutoff is a conserved viral strategy to dismantle cellular defenses, yet the molecular orchestrators in large DNA viruses remain poorly defined. Through a systematic functional screen of the monkeypox virus (MPXV) proteome, we identify M2 as a potent, multifunctional effector that executes a global blockade of host gene expression. Unlike its assembly-centric homologs across the orthopoxvirus genus, M2 localizes not only to the well-characterized endoplasmic reticulum but also to the nuclear envelope, where it may function as a molecular chokepoint, obstructing bidirectional nucleocytoplasmic transport. Concurrently, M2 expression is also associated with altered Akt/mTOR/4EBP1 signaling axis, which may contribute to reduced cap-dependent translation. Intriguingly, M2 may induce a 'transcriptional trap', triggering a robust but futile ERK-dependent activation of AP-1-mediated stress responses that are decoupled from translation. Using recombinant virus engineering, we provide evidence that M2 expression augments viral replication in cell culture. These findings suggest that M2 may contribute to MPXV-mediated host shutoff, although further studies under authentic infection conditions are required to establish causality and define the underlying mechanism. Our study preliminarily reveals an paradigm for viral niche adaptation, in which a single protein coordinates spatial sequestration and biochemical suppression to enact multi-layered host suppression, providing critical candidate targets for therapeutic intervention against emerging orthopoxviruses.