A1 has been shown to interact with BAT2, Flap structure-specific endonuclease 1 and IκBα. Role in Viruses hnRNP A1 is involved in the life cycle of DNA, positive sense RNA, and negative sense RNA viruses are multiple stages post-infection. The proteins role in viral life cycles varies depending on the virus and can even play contradictory roles. In some, it promotes viral replication while in others, it abrogates it. hnRNP A1's anti-viral effect is present in human T-cell lymphotropic virus type I (HTLV-1) cell culture model. hnRNP A1 inhibits the binding of Rex protein to its response element in 3’ long terminal repeat (LTR) of all viral RNAs. Ectopic expression of hnRNP A1 antagonizes post-transcriptional activity of Rex via competitive binding, eliciting an antiviral response against HTLV-1 infection by negatively affecting the rate of viral replication. In the case of Hepatitis C virus (HCV), a positive sense RNA virus, hnRNP A1 interacts with a crucial region near the 3’ end of the virus’ open reading frame (ORF) called the cis-acting replication element. When hnRNP A1 is upregulated, HCV replication decreases and when hnRNPA1 is downregulated, HCV replication increases. hnRNP A1's pro-viral effect is present in the Sindbis virus (a positive sense RNA virus) infection model. hnRNP A1 has been found redistributed in the cytoplasmic site of viral replication bound to the 5’ UTR region of the viral RNA, promoting synthesis of negative-strand RNA. hnRNP A1 has a similar role in porcine epidemic diarrhea virus (PEDV) infection in which hnRNP A1 co-immunoprecipitates with PEDV nucleocapsid protein during infection. hnRNP A1 also bound to terminal leader sequences and intergenic sequences that are crucial for efficient viral replication. Similar trends have also been observed in rhinovirus (HRV), enterovirus 71 (EV-71), and avian reovirus (ARV) infections. In the case of some viruses, such as human immunodeficiency virus 1 (HIV-1), contradictory results have been reported in different research studies. Monette et al. reported increased endogenous expression of hnRNP A1 after HIV-1 infection, as enhanced hnRNPA1 levels were seen as favorable for the virus. They also found that down regulation of hnRNPA1 negatively affected viral replication. In contrast, Zahler et al. found that over expression of hnRNP A1 in vitro adversely affected viral replication. As a result, the role of hnRNPA1 in HIV-1's life cycle is somewhat controversial. Role in other disease Mutations in hnRNP A1 are a cause of amyotrophic lateral sclerosis and multisystem proteinopathy.