Single-stranded nucleic acid binding protein that binds preferentially to oligo dC. Major cellular poly(rC)-binding protein. Binds also poly(rU). Negatively regulates cellular antiviral responses mediated by MAVS signaling (PubMed:19881509). It acts as an adapter between MAVS and the E3 ubiquitin ligase ITCH, therefore triggering MAVS ubiquitination and degradation (PubMed:19881509). (Microbial infection) In case of infection by poliovirus, binds to the viral internal ribosome entry site (IRES) and stimulates the IRES-mediated translation (PubMed:12414943, PubMed:24371074). Also plays a role in initiation of viral RNA replication in concert with the viral protein 3CD (PubMed:12414943). Identified in a mRNP complex, at least composed of DHX9, DDX3X, ELAVL1, HNRNPU, IGF2BP1, ILF3, PABPC1, PCBP2, PTBP2, STAU1, STAU2, SYNCRIP and YBX1. Interacts with IFIH1 and RNF135. Interacts with MAVS (via C-terminus) and ITCH (via WW domains). Loosely bound in the nucleus. May shuttle between the nucleus and the cytoplasm. Detected in all tissues examined. The KH domains mediates poly(C) binding. Phosphorylated. The non-phosphorylated form(s) exhibited the strongest poly(rC)-binding activity. (Microbial infection) Proteolyticaly cleaved by picornavirus proteinase 3CD. Extended N-terminus.