Two Holliday junction resolving enzymes in Sulfolobus solfataricus

Holliday junction resolving enzymes bind specifically to four-way DNA junct ions created by the process of homologous recombination, cleaving them to y ield recombinant duplex DNA products. Homologous recombination is known to occur in the third domain of life, the archaea, and may constitute a simpli fied model for the corresponding eucaryal pathway, but has not been well ch aracterised. Identification of a gene encoding an archaeal Holliday junctio n resolving enzyme, Hjc, has recently been reported in the euryarchaea, and an activity has been observed in the hyperthermophilic crenarchaeote Sulfo lobus solfataricus. Here we report the identification, heterologous express ion and characterisation of the Hjc protein from Sulfolobus. We demonstrate that Sulfolobus has two distinct junction resolving enzymes, Hjc and Hje, with differing substrate specificities. (C) 2000 Academic Press.