The protein “BCL-2-associated athanogene-1” (BAG-1), which exists in multiple isoforms, promotes cancer cell survival and is overexpressed in many different cancers. As a result, BAG-1-targeted therapy appears to be a promising strategy with which to treat cancer. It has previously been shown that the 5′UTR of the BAG-1 mRNA contains a guanine rich region that folds into a G-quadruplex structure which can modulate both its cap-dependent and its cap-independent translation. Accumulating data regarding G-quadruplex binding proteins suggest that these proteins can play a central role in gene expression. Consequently, the identification of the proteins that could potentially bind to the G-quadruplex of the BAG-1 mRNA was undertaken. Label-free RNA pulldown assays were performed using protein extracts from colorectal cancer cells and this leads to the detection of RNA G4 binding proteins by LC-MS/MS. The use of G-quadruplex containing RNA, as well as of a mutated version, ensured that the proteins identified were specific for the RNA G-quadruplex structure and not just general RNA binding proteins. Following confirmation of the interaction, the Small Nuclear Ribonucleoprotein Polypeptide A (SNRPA) was shown to bind directly to the BAG-1 mRNA through the G-quadruplex, and knock down experiments in colorectal cancer cells suggested that it can modulate the expression level of BAG-1.

存在于多种同工型中的蛋白质“ BCL-2-associated athanogene-1”（BAG-1）可促进癌细胞存活，并在许多不同的癌症中过表达。结果，靶向BAG-1的治疗似乎是治疗癌症的有前途的策略。以前已经证明，BAG-1 mRNA的5'UTR包含一个富含鸟嘌呤的区域，该区域折叠成一个G四联体结构，可以调节其帽依赖性和帽依赖性翻译。关于G-四链体结合蛋白的积累数据表明，这些蛋白可以在基因表达中发挥核心作用。因此，鉴定了可能与BAG-1 mRNA的G-四链体结合的蛋白质。使用来自结直肠癌细胞的蛋白质提取物进行了无标记RNA下拉测定，这导致通过LC-MS / MS检测RNA G4结合蛋白。使用含有G-四链体的RNA以及突变形式，可确保所鉴定的蛋白质对RNA G-四链体结构具有特异性，而不仅仅是一般的RNA结合蛋白。确认相互作用后，小核糖核蛋白多肽A（SNRPA）通过G-四链体直接与BAG-1 mRNA结合，在大肠癌细胞中的敲除实验表明它可以调节BAG的表达水平-1。确保所鉴定的蛋白质对RNA G四联体结构具有特异性，而不仅仅是一般的RNA结合蛋白。确认相互作用后，小核糖核蛋白多肽A（SNRPA）通过G-四链体直接与BAG-1 mRNA结合，在大肠癌细胞中的敲除实验表明它可以调节BAG的表达水平-1。确保所鉴定的蛋白质对RNA G四联体结构具有特异性，而不仅仅是一般的RNA结合蛋白。确认相互作用后，小核糖核蛋白多肽A（SNRPA）通过G-四链体直接与BAG-1 mRNA结合，在大肠癌细胞中的敲除实验表明它可以调节BAG的表达水平-1。