Abstract

Purpose : To characterize the response to X-irradiation of the poly ADP-ribosylation system in two closely related murine lymphoma sublines, L5178Y-R (LY-R) and L5178Y-S (LY-S), with differential sensitivity to various DNA damaging agents (UV-C and ionizing radiation, hydrogen peroxide).

Materials and methods : LY cells were X-irradiated (2 Gy). NAD + was determined in cell extracts by high-pressure liquid chromatography. ADP-ribose polymers were purified and analysed by densitometry after polyacrylamide gel electrophoresis. Nuclear matrix proteins were separated by SDS-polyacrylamide gel electrophoresis and processed for ADP-ribose polymer blots to estimate their ability to bind poly(ADP-ribose).

Results : In the radiosensitive LY-S cells, the constitutive levels of ADP-ribose polymers were twofold higher than in radioresistant LY-R cells, but unresponsive to a challenge with 2 Gy X-rays. The concentrations of NAD + - the substrate for poly(ADP-ribose) synthesis - were identical in the two cell lines. X-rays (2 Gy) depleted NAD + only in LY-S cells. These cells also produced shorter poly(ADP-ribose) molecules as compared with LY-R cells. Nuclear matrix preparations of LY-S cells exhibited lower poly(ADP-ribose)-binding capacity than those of LY-R cells.

Conclusion : The results demonstrate disturbances in the poly ADP-ribosylation response of the radiosensitive LY-S cells and reduced poly(ADP-ribose)-binding affinity of the nuclear matrix of these cells.