The Capicua-Ataxin 1L DNA Binding Transcriptional Repressor Complex Serves as a Gatekeepers of Cell Autonomous Antiviral Responses[Human ATAC-Seq]

Early detection of viral infection and rapid activation of host antiviral defenses are critical for limiting viral replication and spread. At a cellular level, this is achieved through host pattern recognition receptors that sense viral nucleic acid as foreign and initiate antiviral defenses through transcriptional upregulation of antiviral cytokines interferons (IFNs) and interferon stimulated genes (ISGs). However, aberrant production of IFN in the absence of viral infection leads to auto-inflammation and can be detrimental to the host. Here, we show that the DNA binding transcriptional repressor complex composed of Capicua (CIC) and Ataxin-1 like (ATXN1L) bind to 8-nucleotide motif near IFN and ISG promoters and block aberrant expression under homeostasis. However, during respiratory viral infections, this active repression is relieved by rapid degradation of the CIC-ATXN1L complex via the activation Mitogen‑activated protein kinase (MAPK) pathway, thereby priming the host cells ready to mount robust antiviral responses through canonical interferon regulatory factors (IRF), and signal transducer and activator of transcription (STAT) transcription factors. Importantly, murine Cic-Atxn1L also repress expression from IFN and ISGs promoters, demonstrating the conservation of this regulatory mechanism in murine species. Together, our studies define a new paradigm for regulation of IFN and ISGs through the evolutionarily conserved CIC-ATXN1L DNA binding transcription repressor complex under homeostasis and viral infection conditions.