RNA-binding protein implicated in the regulation of several post-transcriptional events. Involved in pre-mRNA alternative splicing, mRNA translation and stability. Mediates exon inclusion and/or exclusion in pre-mRNA that are subject to tissue-specific and developmentally regulated alternative splicing (By similarity). Specifically activates exon 5 inclusion of cardiac isoforms of TNNT2 during heart remodeling at the juvenile to adult transition (By similarity). Acts as both an activator and repressor of a pair of coregulated exons: promotes inclusion of the smooth muscle (SM) exon but exclusion of the non-muscle (NM) exon in actinin pre-mRNAs (By similarity). Activates SM exon 5 inclusion by antagonizing the repressive effect of PTB (By similarity). Promotes exclusion of exon 11 of the INSR pre-mRNA (By similarity). Inhibits, together with HNRNPH1, insulin receptor (IR) pre-mRNA exon 11 inclusion in myoblast (By similarity). Increases translation and controls the choice of translation initiation codon of CEBPB mRNA (By similarity). Increases mRNA translation of CEBPB in aging liver. Increases translation of CDKN1A mRNA by antagonizing the repressive effect of CALR3 (By similarity). Mediates rapid cytoplasmic mRNA deadenylation (By similarity). Recruits the deadenylase PARN to the poly(A) tail of EDEN-containing mRNAs to promote their deadenylation (By similarity). Required for completion of spermatogenesis. Binds to (CUG)n triplet repeats in the 3'-UTR of transcripts such as DMPK and to Bruno response elements (BREs) (By similarity). Binds to muscle-specific splicing enhancer (MSE) intronic sites flanking the alternative exon 5 of TNNT2 pre-mRNA (By similarity). Binds to AU-rich sequences (AREs or EDEN-like) localized in the 3'-UTR of JUN and FOS mRNAs. Binds to the IR RNA (By similarity). Binds to the 5'-region of CDKN1A and CEBPB mRNAs (By similarity). Binds with the 5'-region of CEBPB mRNA in aging liver. May be a specific regulator of miRNA biogenesis. Binds to primary microRNA pri-MIR140 and, with CELF2, negatively regulates the processing to mature miRNA (By similarity). Associates with polysomes (By similarity). Interacts with HNRNPH1; the interaction in RNA-dependent. Interacts with PARN (By similarity). Component of an EIF2 complex at least composed of CELF1/CUGBP1, CALR, CALR3, EIF2S1, EIF2S2, HSP90B1 and HSPA5. RNA-binding activity is detected in both nuclear and cytoplasmic compartments. Experimental confirmation may be lacking for some isoforms. Expressed in skeletal muscle, uterus, diaphragm, lung, spleen, testis, mammary gland, adipose, eye and brain (at protein level). Strongly expressed in aging liver (at protein level). Expressed in lung, stomach, heart to very low levels (at protein level). Expressed in germ cells of the seminiferous tubules except in the central region that contains the elongated spermatids and spermatozoa (at protein level). Expressed in Leydig cells of the interstitial tissue (at protein level). Expressed in the heart, skeletal muscle, testis (from spermatogonia to round spermatids), spleen, lung, neocortex, cerebellar cortex, hippocampus and other areas, abundant in the putamen, and poorly expressed in the thalamus and in the brain stem. Expressed in heart, muscle, brain, liver, thigh, stomach and lung at 14 dpc (at protein level). Expressed from the two-cell to blastocyst stages. Expressed in tail region, somites, cephalic structures and limb buds at 10.5 dpc. Its RNA-binding activity on CEBPB mRNA increases in response to EGF. RRM1 and RRM2 domains preferentially target UGU(U/G)-rich mRNA elements. Phosphorylated. Phosphorylated by CDK4 on Ser-302. Its phosphorylation status increases in aging liver and is important for the formation of the EIF2 complex and activation of CEBPB mRNA translation. Hyperphosphorylated in the EIF2 complex. EGFR signaling regulates its phosphorylation status in epithelial cells. Belongs to the CELF/BRUNOL family.