Biotin-isoxazole (1377605-22-5) precipitates hundreds of RNA-binding proteins with significant overlap to the constituents of RNA granules.1,2 In one study roughly 580 nuclear proteins were identified as being precipitated by B-Isox including TAF15, RNA polymerase II (largest subunit), numerous subunits of the mediator complex as well as a variety of enzymes involved in epigenetic modification of histones.3? SR domains were found to be the determinant that facilitates B-Isox precipitation.4 Also allows for the fractionation / isolation of SG-associated proteins and RNA precipitates.5