The enterohemorrhagic Escherichia coli insertion sequence-excision enhancer protein is a DNA polymerase with microhomology-mediated end-joining activity.

Bacterial genomes contain an abundance of transposable insertion sequence (IS) elements that are essential for genome evolution and fitness. Among them, IS629 is present in most strains of enterohemorrhagic Escherichia coli O157 and accounts for many polymorphisms associated with gene inactivation and/or genomic deletions. The excision of IS629 from the genome is promoted by IS-excision enhancer (IEE) protein.