The FACT complex associates with the RPA complex at viral replication compartments to promote adenovirus infection

We have determined that the FACT (Facilitates Chromatin Transcription) complex components, SPT16 and SSRP1, associate with both the RPA (Replication Protein A) complex and adenovirus DNA-binding protein (DBP) within viral replication compartments (VRCs) during both human adenovirus 5 (Ad5) and adenovirus 12 (Ad12) infection, and possess proviral activities. Inactivation of FACT by the curaxin, CBL0137, reduces Ad5 and Ad12 E1A-dependent induction of early gene products, while inhibition of FACT by siRNA similarly affected Ad5 gene product synthesis, but differentially affected Ad12 gene product expression. A consistent feature of FACT inhibition, however, was a significant reduction in the protein levels of DBP, which correlated positively with a significant reduction in the formation of VRCs during infection, and the production of new, infectious virus. Pertinently, the inactivation of FACT with CBL0137 or siRNA increased the levels of the p53 protein and p53 target gene product, p21^CIP1/WAF1; FACT inhibition by CBL0137 limited the ability of E1A to induce S-phase in Ad-infected cells. We propose, therefore, that the FACT complex cooperates with E1A to promote early gene expression and create an environment conducive to viral replication, while FACT inactivation, through its ability to modulate VRC formation and cell cycle progression, has antiviral properties.IMPORTANCEViruses have evolved to inhibit cellular proteins and pathways that possess inherent antiviral activity and utilize cellular proteins and pathways that possess proviral activities. Identification and characterization of both antiviral and proviral factors are therefore important toward understanding the biology of virus-host interactions and the generation of novel antivirals. Viral replication compartments (VRCs) are essential for a productive infection; they are highly dynamic, spatially organized structures to which both proviral and antiviral cellular factors are recruited. Adenoviruses recruit cellular proteins, such as the RPA complex, to VRCs, though their precise roles during infection are poorly understood. Identification and characterization of cellular, RPA complex-associated proteins at VRCs are important to understanding their multifaceted roles during infection. The studies described herein further our understanding of the relationship between adenovirus, the RPA complex, and VRCs during infection, establish proviral roles for the FACT complex, and identify FACT inhibitors as potential antivirals for adenovirus infection.