Unexpected efficient ab initio DNA synthesis at low temperature by using thermophilic DNA polymerase

DNA was synthesized in the absence of DNA or RNA as template (or primer) from dNTPs at relatively low temperatures (25 approximately 50 degrees C) by thermophilic Vent DNA polymerase whose proper reaction temperature for primer extension is 70 approximately 80 degrees C. Unexpectedly, the ab initio DNA synthesis was even more efficient at 50 degrees C as compared with that at 70 degrees C. Interestingly, the ab initio DNA synthesis by Vent (exo), a mutant version of Vent DNA polymerase lacking of 3' --> 5' exonuclease activity, became much less efficient, and it could only carry out ab initio DNA synthesis after a long incubation time. This remarkable difference between Vent and Vent (exo) indicates that the exonuclease activity domain of Vent may play an important role at the initiation step of ab initio DNA synthesis.