The Future of Cross-Linking and Immunoprecipitation (CLIP).

To understand the assembly and functional outcomes of protein-RNA regulation, it is crucial to precisely identify the positions of such interactions. Cross-linking and immunoprecipitation (CLIP) serves this purpose by exploiting covalent protein-RNA cross-linking and RNA fragmentation, along with a series of stringent purification and quality control steps to prepare complementary DNA (cDNA) libraries for sequencing. Here we describe the core steps of CLIP, its primary variations, and the approaches to data analysis. We present the application of CLIP to studies of specific cell types in genetically engineered mice and discuss the mechanistic and physiologic insights that have already been gained from studies using CLIP. We conclude by discussing the future opportunities for CLIP, including studies of human postmortem tissues from disease patients and controls, RNA epigenetic modifications, and RNA structure. These and other applications of CLIP will continue to unravel fundamental gene regulatory mechanisms while providing important biologic and clinically relevant insights.