Musashi1 (MSI1) is a highly conserved RNA binding protein with important functions in stem cell maintenance, nervous system development and tumorigenesis. MSI1 inhibit translation initiation of its target mRNA, m-Numb, by competing with eIF4G for Poly A Binding Protein. MSI1 is mainly expressed in stem and progenitor cells from different tissues in mammals, and a decrease occurs as cells commit to lineage differentiation. Recently, expression of MSI1 in mature photoreceptors and retinal pigment epithelium cells was found and its expression in those cells are absolutely necessary for survival of photoreceptors. Abreu and his coworkers performed a RIP-Chip analysis and revealed that MSI1 associated mRNAs are belong to two main functional categories pertinent to tumorigenesis.
Posttranscriptional regulation of gene expression is a ribonucleoprotein-driven process, which involves RNA binding proteins (RBPs) and non-coding RNAs that affect splicing, nuclear export, subcellular localization, mRNA decay and translation. The RNP Immunoprecipitation-Chip (RIP-Chip), RIP-Seq and RIP-RTPCR allow the identification of multiple RNA targets of RBPs globally and within the context of a cell extract. Antibodies specific to the RNA binding protein of interest are used to co-immunoprecipitate the RNA binding protein and the associated subset of mRNAs. The mRNA content is interrogated using standard microarray or sequencing technology. RIP-Certified Antibody is validated for use in RNP Immunoprecipitation (RIP) in conjunction with the RIP-Assay Kit distributed from MBL. Its ability to immunoprecipitate mRNAs and RBPs complex was confirmed by quantitative and qualitative analysis on NanoDrop, Bioanalyzer and RT-PCR or microarray.