A protocol for CRISPR-mediated activation and repression of human endogenous retroviruses in human pluripotent stem cells

Human endogenous retroviruses (HERVs) comprise many regulatory elements and can regulate host gene activity at different expression levels via multiple mechanisms. Here, we introduce a step-by-step protocol to activate or repress transcription of HERV-K(HML-2) elements using the CRISPRa and CRISPRi technologies in human embryonic stem cells. This protocol can help deciphering the functional role of HERV-K(HML-2) elements in critical biological processes. The protocol may easily be adapted to other cell lines and HERV groups with relatively low sequence heterogeneity.