The Stress Granule Marker IF Antibody Sampler Kit provides an economical means of evaluating total levels of stress granule-associated proteins. The kit includes enough antibodies to perform two western blot experiments with each primary antibody.

Stress granules (SGs) are cytoplasmic condensates that form at sites of stalled mRNA translation in response to various cellular stressors. SGs are composed of translationally inactive 48S preinitiation complexes (PICs), untranslated mRNA, and a complex mixture of RNA-binding proteins (RBPs). Two key mediators of SG assembly are the RBPs Ras-GTPase-activating protein-binding proteins 1 and 2 (G3BP1/2), which bind to excess mRNA and recruit additional SG-associated proteins. Overexpression of either G3BP1 or G3BP2 is enough to induce SG formation even in the absence of stress, and reduced levels of G3BP1 or G3BP2 protein severely inhibit SG formation, highlighting their crucial role in this process (1-4). Additional SG-associated proteins include TIA-1-related protein (TIAR), fragile X mental retardation protein (FMRP), and ubiquitin-associated protein 2-like (UBAP2L). TIAR is a member of the RNA-recognition motif (RRM) family of RBPs (5,6). In response to cellular stress, TIAR associates with G3BP1/2 and its family member TIA-1 to form SG condensates (7,8). The two major isoforms of TIAR are the products of alternative mRNA splicing (9,10). FMRP (also known as FMR1) and its two autosomal homologs (FXR1 and FXR2) all bind RNA and play a role in the pathogenesis of fragile X syndrome (11-13). Each of these related proteins can associate with one another as well as form homodimers (13). FMRP can act as a translation regulator and is a component of RNAi effector complexes (RISC), suggesting a role in gene silencing (14). In addition, FMRP, FXR1, and FXR2 are components of SGs and have been implicated in the translational regulation of mRNAs (15). UBAP2L is a ubiquitous and highly conserved protein containing an N-terminal ubiquitin-associated (UBA) domain involved in the ubiquitin-proteasome system (UPS) and aggregate formation induced by proteasome inhibitors (16). It can also interact with the Polycomb group protein BMI1 to form a Polycomb subcomplex and regulate hematopoietic stem cell activity (17). UBAP2L is essential for the formation of SGs, and some studies suggest that arginine methylation by PRMT1 inhibits UBAP2L interaction with SG elements and overall SG assembly (18-20).