ARGLU1 is a negative regulator of the adenoviral replicative cycle

We have previously reported that human adenovirus E1A interacts with ARGLU1, a small disordered cellular protein. The consequences of this interaction for virus replication were unclear. E1A is the first protein produced during adenovirus infection. Via protein-protein interactions, E1A modifies the cellular environment to create optimal conditions for viral replication. To better understand the molecular mechanisms driving viral infection, we further investigated the functional consequences of the interaction between ARGLU1 and E1A. ARGLU1 interacts with E1A directly as determined by a GST-pulldown assay with recombinant proteins. Importantly, ARGLU1 was found to act as a transcriptional repressor when it was localized to viral promoters. Repression was driven by enhanced promoter-proximal RNA polymerase II pausing. Significantly, ARGLU1-induced repression of viral promoters is likely an unintended consequence of ARGLU1 binding to E1A, as a mutant of E1A (<i>dl</i>1102), unable to bind to ARGLU1, did not show reduced viral gene expression. Furthermore, ARGLU1 was found to colocalize with E1A in infected cell nuclei. Finally, the binding of E1A to ARGLU1 appears to reduce DNA damage repair in bleomycin-treated and adenovirus-infected cells, suggesting that E1A binding to ARGLU1 is important for DNA damage response inhibition. Overall, this study underscores the complexity of virus-host interactions and reveals a novel role for ARGLU1 during adenoviral infection.IMPORTANCEThis study uncovers a novel antiviral role for ARGLU1, known for its involvement in splicing, transcriptional regulation, and DNA damage repair. Our study demonstrates that ARGLU1 functions as a viral restriction factor by reducing virus growth through the inhibition of viral gene expression and enhanced DNA damage response, leading to reduced viral growth. These findings not only highlight an important role for ARGLU1 in host antiviral mechanisms but also emphasize the utility of adenovirus as a tool to uncover critical cellular pathways.