Circadian Clock Gene Modulation and Selective Reprogramming in Response to Virus Infection

The circadian clock regulates fundamental cellular processes that include the host response to infection. However, the intersection of the circadian clock and the mechanisms that drive antiviral immunity remains poorly understood. Copy-back viral genomes (cbVGs) generated during virus replication strongly stimulate immunity during infection with negative-sense RNA viruses. Here, we demonstrate at the single cell level that A549 lung epithelial cells, commonly used to model lung infections, sustain circadian rhythms and upon infection with Sendai virus (SeV) progressively remodel the circadian clock through an innate immune response driven primarily by cbVGs. Furthermore, we show that cbVG-driven changes in circadian gene expression are mediated through two distinct innate immune sensing pathways: the RIG-I adaptor MAVS is required for preferential induction of the BMAL1 paralog ARNTL2, whereas the double-stranded RNA sensor PKR is required for the cbVG-specific induction of the negative-feedback regulators NR1D1, NR1D2, and PER1. A similar cbVG-specific signature was observed during respiratory syncytial virus infection, suggesting that cbVG-driven circadian gene regulation is not unique to SeV. In addition, we established through gain- and loss-of-function experiments that ARNTL2 is functionally required for amplifying the transcriptional response to infection, with selective effects on the expression of specific antiviral genes, including CCL5. Together, these findings establish innate immune signaling triggered by cbVGs as selective driver of circadian clock gene expression during viral infection through distinct sensing pathways and identify ARNTL2 as a previously unrecognized regulator of virus-induced host transcriptional responses.