G-quadruplex RNA pulldown followed by mass spectrometry. G4A4 oligoribonucleotide (5’-AAAAAAGGGGAAAAGGGGAAAAGGGGAAAAGGGGAAAAAA-3’) was biotinylated and folded in either K+ or Li+ containing buffers, causing folding of G-quadruplex (K+) or destabilization of the secondary structure (Li+). G4A4 pulldown was used to identify G4-RNA binding proteins from K562 human cell line nuclear extracts, interacting in structure-dependent manner.