ATP- and magnesium-dependent helicase that plays an essential role in innate immunity. Participates in the DNA-triggered cGAS/STING pathway by promoting the DNA binding and activation of CGAS. Enhances also DDX58-induced type I interferon production probably by helping DDX58 at sensing pathogenic RNA. In addition, plays an essential role in stress granule formation. Unwinds preferentially partial DNA and RNA duplexes having a 17 bp annealed portion and either a hanging 3' tail or hanging tails at both 5'- and 3'-ends. Unwinds DNA/DNA, RNA/DNA, and RNA/RNA substrates with comparable efficiency. Acts unidirectionally by moving in the 5' to 3' direction along the bound single-stranded DNA. Phosphorylation-dependent sequence-specific endoribonuclease in vitro. Cleaves exclusively between cytosine and adenine and cleaves MYC mRNA preferentially at the 3'-UTR. ATP + H2O = ADP + H(+) + phosphate ATP + H2O = ADP + H(+) + phosphate Mg(2+) is required for helicase activity. Homodimer and oligomer (By similarity). Component of a TAU mRNP complex, at least composed of IGF2BP1, ELAVL4 and G3BP1 (By similarity). Binds to the SH3 domain of Ras GTPase-activating protein (RASA1) in proliferating cells (By similarity). No interaction in quiescent cells (By similarity). Interacts (via NTF2-like domain) with USP10. Interacts with RPTOR and SPAG5; this complex is increased by oxidative stress. Interacts with ATXN2L. Interacts with STYXL1. Interacts with CGAS (via N-terminus); this interaction promotes the DNA-binding and activation of CGAS. Interacts (via C-terminus) with DDX58. Interacts (via NTF2-like domain) with CAPRIN1. Interacts with PABPC1 (By similarity). Cytoplasmic in proliferating cells, can be recruited to the plasma membrane in exponentially growing cells. Cytosolic and partially nuclear in resting cells. Recruited to stress granules in response to arsenite treatment. The unphosphorylated form is recruited to stress granules. HRAS signaling contributes to this process by regulating G3BP dephosphorylation. The NTF2 domain mediates multimerization. Phosphorylated exclusively on serine residues. Hyperphosphorylated in quiescent fibroblasts. Hypophosphorylation leads to a decrease in endoribonuclease activity. RASA1-dependent phosphorylation of Ser-149 induces a conformational change that prevents self-association. Dephosphorylation after HRAS activation is required for stress granule assembly. Ser-149 phosphorylation induces partial nuclear localization (By similarity).