DNA Polymerase Iota-Like Activity in Crude Cell Extracts of Different Mouse Organs

Abstract

The recently discovered DNA polymerase iota differs greatly from the numerous eukaryotic and prokaryotic DNA polymerases known previously in its ability to catalyze error-prone DNA synthesis. Using homogeneous preparations of the enzyme, it was shown previously that DNA polymerase iota incorporated preferentially dGMP opposite the thymidine of the template in the growing DNA chain. To elucidate the role of this enzyme in the mammals, its activity was assayed in crude cell extracts of different mouse organs. It is shown that the extracts of the brain and testis cells exhibit the highest activity of DNA polymerase iota, which is not in agreement with the results of other authors. The data suggest that the tissue specific expression of DNA polymerase iota is regulated to a significant degree at the posttranscriptional and posttranslational levels.

Enhanced Activity of DNA Polymerase Iota in Mouse Brain Cells Is Associated with Aggressiveness

“…Our results showed that the activity of this enzyme in mouse brain cells is significantly greater than in the majority of other organs [5]. This finding suggests that the high activity of Pol ι in mouse brain cells should play a functional role.…”

“…The analysis of cell extracts of mouse liver, heart, lungs, spleen, and pancreas, performed under the same conditions as the analysis of brain cell extracts, did not reveal Pol ι activity [5], although other DNA polymeras es were detected well under these conditions.…”

“…In particular, unlike other DNA polymerases, Pol ι breaks the Watson-Crick rule and preferentially incorporates deoxyguanosine monophosphate into the growing DNA strand opposite to thymidine of the template [2 4]. The biological functions of Pol ι remain unknown because diseases or susceptibil ities to diseases associated with mutations in the gene encoding this enzyme in humans have not been described.We recently studied the activity of Pol ι immediately in mouse tissue extracts [5]. The analytical method used for this purpose was based on the ability of Pol ι to prefer entially incorporate dGMP opposite to T of the template.…”

“…1). A 17 mer oligonucleotide was labeled with 32 P at the 5′ end, and brain extracts were obtained as described in [5]. Animals were sacrificed under standard conditions by a sharp dislocation of the cervical vertebrae.…”

“…We recently studied the activity of Pol ι immediately in mouse tissue extracts [5]. The analytical method used for this purpose was based on the ability of Pol ι to prefer entially incorporate dGMP opposite to T of the template.…”