[Expression of ORIGIN-like sequence in mammalian cells]

There are some genes whose expression increases in non-proliferating hepatocytes after whole-body X-irradiation. We suppose that some of them participate in cell division regulation. To verify our postulate we have studied expression of autonomously replicating sequence pDARC1 in normal, irradiated and dividing rat hepatocytes. We have succeeded earlier in cloning the autonomously replicating sequence pDARC1 and have shown that it could be transcribed in X-irradiated hepatocytes. Here we report on the results of analysis of this sequence expression in dividing mammalian cells. Hybridization with the pDARC1 sequence reveals 4.0 kb mRNA in non-proliferating rat hepatocytes after X-irradiation: this mRNA is absent in normal hepatocytes. Induction of 4.0 kb mRNA is a function of radiation dose; 4.0 kb mRNA content is maximum 6-24 h following whole-body 6 Gy X-irradiation. The 4.0 kb mRNA is also found in dividing rat hepatocytes during the pre-replicative period.