Protocol to study the direct binding of proteins to RNA:DNA hybrids or RNA-DNA chimeras in living cells using cross-linking immunoprecipitation

RNA-binding proteins (RBPs) are involved in many biological processes. The direct interaction between protein and RNA can be studied using cross-linking immunoprecipitation (CLIP) techniques in living cells. Here, we present a protocol to characterize the direct binding of proteins to RNA:DNA hybrids or RNA-DNA chimeras in living cells using CLIP. We describe steps for RNA-protein UV-C crosslinking in living cells, isolating RNA-protein complexes, RNA labeling, and extracting nucleic acid. We then detail procedures for nuclease treatment and nucleic acid migration.