RNA-binding protein involved in modulation of mRNA transcription by Polymerase II (PubMed:16950395). Component of the tRNA-splicing ligase complex and is required for tRNA ligation (PubMed:24870230). May be required for RNA transport (PubMed:24608264). (Microbial infection) In case of infection by influenza virus A (IVA), is involved in viral replication (PubMed:21900157). Homodimer (Probable). Interacts with FAM98A (via N- and C-terminus) (PubMed:28040436). Interacts with NIN; which may prevent phosphorylation of NIN (PubMed:15147888). Interacts with POLR2A (PubMed:16950395). Component of a tRNA-splicing ligase complex with FAM98B, DDX1 and RTCB (PubMed:21311021, PubMed:24870230, PubMed:24608264). (Microbial infection) Interacts with influenza A virus (IAV) RNA polymerase subunits PA, PB1 and PB2, and nucleocapsid NP (PubMed:21900157, PubMed:26864902). Associates with IAV polymerase complexes both in the nucleus and cytosol (PubMed:26864902). Associates with IAV ribonucleoproteins (vRNP) packaged in virions (PubMed:26864902). Interacts with hepatitis C virus core protein p19 (PubMed:21823664). May localize at the centrosome during mitosis (PubMed:15147888). Shuttles between the cytosol and the nucleus: enters into the nucleus in case of active transcription while it accumulates in cytosol when transcription level is low (PubMed:24608264). (Microbial infection) Following influenza A virus (IAV) infection, included in influenza A virions via its association with packaged viral ribonucleoproteins (vRNP) in the nucleus and cytoplasm (PubMed:21900157, PubMed:26864902). Widely expressed. Expressed at high level in heart and skeletal muscle. Expressed at intermediate level in liver, pancreas, fetal brain and fetal lung. Weakly expressed in adult brain, adult lung, placenta, fetal liver and fetal kidney. Overexpressed in many brain tumors. (Microbial infection) Up-regulated specifically following influenza A virus (IAV) infection in a viral replication-dependent manner (at protein level) (PubMed:26864902). Belongs to the RTRAF family.