G3BP1 and infection: To determine whether BPIV3 infection affected the SG-nucleating protein G3BP1, intracellular G3BP1 mRNA levels were examined by quantitative reverse transcriptase PCR (qRT-PCR)at differen.t infection times, and protein expression was examined using a G3BP1-specific antibody to label the BPIV3-N protein as an indicator of viral replication.