Small stable RNA level depends on the physiological state of the cell.

The level of 5S rRNA and tRNAi(Met)1 synthesized by RNA polymerase III was investigated in human epidermoid carcinoma cells A431 at different physiological states: low and high proliferation and apoptosis. The real-time RT-PCR method using SYBR Green I was applied to measure certain RNA species in total cellular RNA. The share of 5S rRNA was practically the same in slowly and actively proliferating A431 cells, but increased about 2.5-fold in apoptotic cells. The share of initiator tRNAi(Met)1 in actively proliferating and apoptotic cells was 1.5-2.0 times higher than in slowly proliferating cells. Our results suggest a possible existence of special mechanisms regulating RNA polymerase III-directed transcription from different type promoters in accordance with the physiological state of the cell.