Modulation of expression of virus-like elements following exposure of mice to high- and low-LET radiations.

Modulation of virus expression has been reported following exposure to a variety of cellular stresses, including UV radiation and heat-shock. The experiments reported here were designed to examine expression of endogenous VL30 (virus-like 30 S) elements following exposure of whole mice to ionizing radiations. Whole mice were exposed to doses of neutrons (50 cGy) or gamma-rays (300 cGy) shown to be equally efficient in cancer production in the whole animal, and tissues were harvested at 10 and 60 min following completion of the exposure. RNA extracted from these tissues and from tissues of untreated controls was examined for VL30 RNA accumulation by dilution dot blot and Northern blot analyses. These studies revealed that neutrons repressed VL30 RNA accumulation evident within 10 min following exposure in brain, gut, thymus and spleen but not in liver, in which VL30 RNA was unaffected by radiation exposure. During this same time interval, gamma-rays induced VL30 expression in gut and brain and to a lesser extent in liver. These experiments suggest the presence of a differential molecular response following whole-body exposure to high- versus low-LET radiations. In addition, this work demonstrates that ionizing radiations may affect expression of murine endogenous viral sequences.