Dual modes of CRISPR-associated transposon homing

• Main Authors: Saito, Makoto (Author), Ladha, Alim (Author), Strecker, Jonathan (Author), Faure, Guilhem (Author), Neumann, Edwin (Author), Altae-Tran, Han (Author), Macrae, Rhiannon K. (Author), Zhang, Feng (Author)
• Format: Article
• Language: English
• Published: Elsevier BV, 2022-05-16T19:19:43Z.
• Subjects: Article
• Online Access: Get fulltext

 Tn7-like transposons have co-opted CRISPR systems, including class 1 type I-F, I-B, and class 2 type V-K. Intriguingly, although these CRISPR-associated transposases (CASTs) undergo robust CRISPR RNA (crRNA)-guided transposition, they are almost never found in sites targeted by the crRNAs encoded by the cognate CRISPR array. To understand this paradox, we investigated CAST V-K and I-B systems and found two distinct modes of transposition: (1) crRNA-guided transposition and (2) CRISPR array-independent homing. We show distinct CAST systems utilize different molecular mechanisms to target their homing site. Type V-K CAST systems use a short, delocalized crRNA for RNA-guided homing, whereas type I-B CAST systems, which contain two distinct target selector proteins, use TniQ for RNA-guided DNA transposition and TnsD for homing to an attachment site. These observations illuminate a key step in the life cycle of CAST systems and highlight the diversity of molecular mechanisms mediating transposon homing.