Self-ligation without DNA ligase possible !! How??
I have a clone wherein the insert of 1.5 kb (NdeI-NdeI) was in reverse orientation.
Hence, I cut out the insert by doing NdeI digestion, heat inactivated the enzyme and did a transformation into XL-1blue cells. Once I started doing transformation, I realized that I had not set up a ligation reaction for re-annealing of the digested fragments. Nevertheless, I continued with what was evidently a lost cause. However, I got a couple of colonies on the plate and upon screening found 2 with the insert in the correct orientation. Lucky. However, what I do not comprehend is how did the digested fragments ligate when I never added any DNA ligase? I thought ATP and ligase are absolutely required for the phosphodiester bond formation and hence religation. Could anyone please shed some light on it?