Inhibits programmed -1 ribosomal frameshifting (-1PRF) of a variety of mRNAs from viruses, such as HIV1, and cellular genes, such as PEG10. Interacts with the -1PRF signal of target mRNA and translating ribosomes and causes premature translation termination at the frameshifting site (PubMed:30682371). Regulates HIV1 GAG-POL expression by inhibiting -1PRF (PubMed:30682371). Exhibits antiviral activity against dengue virus (DENV) and can inhibit the replication of all DENV serotypes. May block the protein translation of DENV RNA via its association with cellular mRNA-binding proteins and viral RNA. Interrupts also Zika virus replication by promoting viral NS3 degradation via a lysosome-dependent pathway (PubMed:32150556). Can also limit the replication of hepatitis C virus (HCV) by restricting formation of viral replication organelle, West Nile virus (WNV), Chikungunya virus (CHIKV), herpes simplex virus type 1 (HHV-1), herpes virus type 8 (HHV-8) and human adenovirus (PubMed:26735137, PubMed:27974568, PubMed:30944177, PubMed:32294532). Binds nucleic acids with a higher affinity for ssRNA and ssDNA than for dsDNA (PubMed:27974568). Isoform 4 does not inhibit programmed ribosomal frameshifting (-1PRF). Does not bind to ribosomes. Interacts with PABPC1 (PubMed:26735137). Found in a complex with PABPC1 and LARP1 (PubMed:26735137). Interacts with ELAV1, MOV10 and UPF1; the interactions increase in presence of RNA (PubMed:27974568). Binds to ribosomes (PubMed:30682371). Interacts with GSPT1 (PubMed:30682371). (Microbial infection) Interacts with the human dengue virus DENV proteins NS3 and NS4A. (Microbial infection) Interacts with Zika virus protein NS3; this interaction promotes viral NS3 degradation. Predominantly found in the cytoplasm (PubMed:26735137). After infection, relocalizes to the DENV replication complex in perinuclear regions (PubMed:27974568). Up-regulated by interferon (IFN) treatment (PubMed:26735137, PubMed:27974568, PubMed:30682371, PubMed:32294532). Expression increases in response to DENV infection in an IFN-dependent manner (PubMed:27974568). Belongs to the SHFL family.