Heterogenous nuclear ribonucleoprotein (hnRNP) implicated in mRNA processing mechanisms. Component of the CRD-mediated complex that promotes MYC mRNA stability. Isoform 1, isoform 2 and isoform 3 are associated in vitro with pre-mRNA, splicing intermediates and mature mRNA protein complexes. Isoform 1 binds to apoB mRNA AU-rich sequences. Isoform 1 is part of the APOB mRNA editosome complex and may modulate the postranscriptional C to U RNA-editing of the APOB mRNA through either by binding to A1CF (APOBEC1 complementation factor), to APOBEC1 or to RNA itself. May be involved in translationally coupled mRNA turnover. Implicated with other RNA-binding proteins in the cytoplasmic deadenylation/translational and decay interplay of the FOS mRNA mediated by the major coding-region determinant of instability (mCRD) domain. Interacts in vitro preferentially with poly(A) and poly(U) RNA sequences. Isoform 3 may be involved in cytoplasmic vesicle-based mRNA transport through interaction with synaptotagmins. Component of the GAIT (gamma interferon-activated inhibitor of translation) complex which mediates interferon-gamma-induced transcript-selective translation inhibition in inflammation processes. Upon interferon-gamma activation assembles into the GAIT complex which binds to stem loop-containing GAIT elements in the 3'-UTR of diverse inflammatory mRNAs (such as ceruplasmin) and suppresses their translation; seems not to be essential for GAIT complex function. Isoform 1 is a component of the APOB mRNA editosome complex and interacts with APOBEC1 and A1CF (APOBEC1 complementation factor). Part of a complex associated with the FOS mCRD domain and consisting of PABPC1, PAIP1, CSDE1/UNR, HNRPD and SYNCRIP. Isoform 3 interacts with HNRPR. Interacts with POLR2A hyperphosphorylated C-terminal domain. Isoform 1, isoform 2 and isoform 3 interact with SMN. Isoform 3 interacts through its C-terminal domain with SYT7, SYT8 and SYT9 (By similarity). The non-phosphorylated and phosphorylated forms are colocalized with PAIP1 in polysomes (By similarity). Interacts with HABP4 (PubMed:19523114). Identified in a histone pre-mRNA complex, at least composed of ERI1, LSM11, SLBP, SNRPB, SYNCRIP and YBX1 (By similarity). Identified in the spliceosome C complex. Component of the coding region determinant (CRD)-mediated complex, composed of DHX9, HNRNPU, IGF2BP1, SYNCRIP and YBX1. Identified in a mRNP complex, at least composed of DHX9, DDX3X, ELAVL1, HNRNPU, IGF2BP1, ILF3, PABPC1, PCBP2, PTBP2, STAU1, STAU2, SYNCRIP and YBX1. Identified in a mRNP granule complex, at least composed of ACTB, ACTN4, DHX9, ERG, HNRNPA1, HNRNPA2B1, HNRNPAB, HNRNPD, HNRNPL, HNRNPR, HNRNPU, HSPA1, HSPA8, IGF2BP1, ILF2, ILF3, NCBP1, NCL, PABPC1, PABPC4, PABPN1, RPLP0, RPS3, RPS3A, RPS4X, RPS8, RPS9, SYNCRIP, YBX1 and untranslated mRNAs. Interacts with GTPBP1. Component of the GAIT complex; in humans the complex assembly seems to be a two-step process in which EPRS1 first associates with SYNCRIP to form a pre-GAIT complex which is deficient in GAIT element binding. (Microbial infection) Interacts with minute virus of mice (MVM) NS1 protein. The tyrosine phosphorylated form bound to RNA is found in microsomes (By similarity). Localized in cytoplasmic mRNP granules containing untranslated mRNAs (By similarity). Expressed predominantly in the nucleoplasm. Expressed predominantly in the nucleoplasm. Expressed predominantly in the nucleoplasm. Ubiquitously expressed. Detected in heart, brain, pancreas, placenta, spleen, lung, liver, skeletal muscle, kidney, thymus, prostate, uterus, small intestine, colon, peripheral blood and testis. The domain containing eight Arg-Gly-Gly repeats (RGG/RXR-box) may be involved in RNA-binding and protein-protein interactions. It is methylated by PRMT1, and essential for nuclear localization. Phosphorylated on tyrosine. The membrane-bound form found in microsomes is phosphorylated in vitro by insulin receptor tyrosine kinase (INSR). Phosphorylation is inhibited upon binding to RNA, whereas the cytoplasmic form is poorly phosphorylated (By similarity). May be due to a competing donor splice site. May be due to a competing donor splice site and to an exon inclusion. May be due to a competing donor splice site and to an exon inclusion. May be due to a competing donor splice site and to an exon inclusion. Contaminating sequence. Potential poly-A sequence starting in position 413.