Proximity-dependent biotinylation detects association between stress granule associated proteins and SARS coronavirus nonstructural protein 1

Severe acute respiratory syndrome coronavirus (SARS-CoV and SARS-CoV-2) nonstructural protein 1 (nsp1) is a critical viral protein that suppresses host gene expression by blocking the assembly of the ribosome on host messenger RNAs (mRNA). Using proximity-dependent biotinylation assay followed by proteomic analyses of biotinylated proteins, we captured multiple dynamic interactions of nsp1 with host cell proteins. In addition to ribosomal proteins, we have identified several mRNA processing proteins, including splicing factors and transcription termination proteins, exosomes- and stress granule (SG) associated proteins. The interactions with transcription termination factors are primarily governed by the C-terminal region of nsp1 and are disrupted by the mutation of K164 and H165 amino acids. We further show that nsp1 associates with SG protein G3BP and colocalizes with G3BP in SGs under sodium arsenite-induced stress for a short period of time. However, the presence of nsp1 disrupts the maturation of SGs over a long period.