THE INHIBITORY-ACTION OF FATTY-ACIDS ON DNA-POLYMERASE-BETA

We found previously that long-chain fatty acids could inhibit eukaryot ic DNA polymerase activities in vitro [1,2]. The purpose of the presen t study was to investigate the mode of this inhibition in greater deta il. Among the C-18 to C-24 fatty acids examined, the strongest inhibit or was a C-24 fatty acid, nervonic acid (NA), and the weakest was a C- 18 fatty acid, linoleic acid (LA). We analyzed the inhibitory effect o f these two fatty acids and their modes of action. For DNA polymerase beta (pol. beta), NA acted by competing with both the substrate-and te mplate-primer, but for DNA polymerase alpha (pol. alpha) or human immu nodeficiency virus type 1 reverse transcriptase (HIV-1 reverse transcr iptase or HIV-RT), NA acted non-competitively. NA-binding to pol. beta could be stopped with a non-ionic detergent, but the binding to pol. alpha or HIV-RT could not. The inhibition mode of LA showed the same c haracteristics, except that the minimum inhibitory dose of the longer chain was much lower. We also tested the effects of NA and LA using po l. beta and its proteolytic fragments, as described by Kumar et al. [3 ,4]. Both of the fatty acids were found to bind to the 8 kDa DNA-bindi ng domain fragment, and to suppress binding to the template-primer DNA . We found that 10 000 times more of either fatty acid was required fo r it to bind to the 31 kDa catalytic domain or inhibit the DNA polymer ase activity. The possible modes of inhibition by these long-chain fat ty acids are discussed, based on the present findings. (C) 1997 Elsevi er Science B.V.