- In vivo functional analysis of the human mitochondrial DNA polymerase POLG expressed in cultured human cells. Spelbrink, J.N., Toivonen, J.M., Hakkaart, G.A., Kurkela, J.M., Cooper, H.M., Lehtinen, S.K., Lecrenier, N., Back, J.W., Speijer, D., Foury, F., Jacobs, H.T. J. Biol. Chem. (2000)