Bioinformatic Identification of CRISPR Leader Motifs

Clustered Regularly Interspersed Short Palindromic Repeats (CRISPR) and CRISPR associated (Cas) proteins serve as a sophisticated adaptive immune system to defend bacteria and archaea from viral infection. CRISPR mediated immunity occurs in three stages which allow the bacteria to adapt and respond to new as well as previously encountered viruses. The initial step of CRISPR adaptation requires the help of the Integration Host Factor (IHF) and a stretch of 200 base pairs known as the CRISPR leader to ensure encounters with new viruses are properly recorded in the host organism’s immunological memory. A bioinformatic analysis of over 15,000 CRISPR leaders reveals that IHF is a prevalent and widespread feature of CRISPR adaptation across several different CRISPR subtypes and host organisms.