X family DNA polymerases can fill short DNA gaps by binding both the 5′ and 3′ ends of the gap. What happens to the template strand is now revealed in the crystal structure of human polymerase λ bound to a 2-nucleotide gap substrate. The template strand is scrunched, with the additional base in an extrahelical position going into an enzyme pocket.
- Miguel Garcia-Diaz
- Katarzyna Bebenek
- Thomas A Kunkel
