Characterization of Mammalian Regulatory Complexes at Single-Locus Resolution Using TINC

In mammalian cells, multiprotein complexes form at specific genomic regulatory elements (REs) to control gene expression, which in turn is ultimately responsible for cellular identity. Consequently, insight into the molecular composition of these regulatory complexes is of major importance for our understanding of any physiological or pathological cellular state or transition. However, it remains extremely difficult to identify the protein complex(es) assembled at a specific RE in the mammalian genome using conventional approaches. We therefore developed a novel single locus isolation technique based on Transcription Activator-Like Effector (TALE) proteins termed TALE-mediated isolation of nuclear chromatin (TINC). When coupled with high-resolution mass spectrometry, TINC enables the identification and characterization of protein complexes formed at any RE of interest. Using the Nanog promoter in mouse embryonic stem cells as proof of concept, this chapter describes in detail the novel TINC methodology as well as subsequent mass spectrometric considerations.