RecA-like activity in mammalian cell extracts of different origin

The occurence of a RecA-like activity similar to the one detected in the fibroblast cell line GM1492 derived from a patient suffering from the autosomal recessive disease Bloom's syndrome has been investigated in cell extracts of different origin. The formation of D-loop containing joint molecules from ΦX174 RFI DNA and fragments of ΦX174 single-stranded DNA by partially purified extracts was measured by a filter binding assay.

The RecA-like activity, dependent on ATP and Mg²⁺, was detected at an elevated level only in the human and rodent cell lines, GM1492 and CHO respectively. The level of activity in DNA-cellulose-purified cell extracts from these cell lines was 4–7-fold higher compared to normal human fibroblasts. Low levels of activity were also detected in extracts from two additional Bloom's syndrome fibroblast cell lines, Fanconi's anemia fibroblasts, virus-(Epstein-Barr virus, Simian virus 40) transformed human cells and human placenta. Cell extracts from rat testis, spleen and calf thymus were also of low activity.