DNA ligase activity in human cell lines from normal donors and Bloom's syndrome patients

DNA ligase activity was studied in several untransformed or virus-transformed human cell lines from normal donors and from Bloom's syndrome (BS) patients. This proneness genetic disease is characterized by several cytological abnormalities and cancer proneness and, recently, some transformed cell lines from these patients were described to present a reduced activity of DNA ligase I. Results presented in this work indicate that: (i) the total DNA ligase activity in crude extract from untransformed or transformed cell lines from several BS patients was significantly higher than in control cells; (ii) the partial purification of the enzyme after gel filtration on fast protein liquid chromatography of crude extracts from lymphoblastoid BS cells showed that the enzyme activity was eluted in a major 180 kDa form in which activity was higher than in control cells; (iii) the activity gel analysis of these enzyme fractions revealed that DNA ligase of human cells was correlated to a major 130 kDa polypeptide and, in BS cells, the extent of the activity of this band was equal or higher than that in control untransformed or transformed cells.