Matrin 3 RRMs are required for activity on HIV-1 RNA. A) Schematic representations of the RRM deletion mutants of Matrin 3. B) Western blot verification of the comparable expression of transfected Matrin 3 deletion mutants. Loadings were normalized to β-actin (bottom panel). C) Expression of wild type HA-Matrin 3 (lane 2), but not HA-Matrin 3 d264-595 (lane 3) nor HA-Matrin 3 d162-595 (lane 4), which lack the RRMs activated HIV-1 gene expression as measured by viral p55 or p24 levels.