ADDITION OF CALMODULIN ANTAGONISTS TO NRK CELLS DURING G1 INHIBITS PROLIFERATING CELL NUCLEAR ANTIGEN EXPRESSION

作者：LOPEZGIRONA A; BOSCH M; BACHS O; AGELL N

来源：Cell Calcium, 1995, 18(1): 30-40.

DOI：10.1016/0143-4160(95)90043-8

The mRNAs of most proteins involved in DNA synthesis show an S phase correlated expression when mammalian cells are stimulated to proliferate from G0. This is the case for proliferating cell nuclear antigen (PCNA), a cofactor of DNA polymerase delta that is essential for the synthesis of the leading and tagging strands of DNA. Normal rat kidney cells re-entering the cell cycle from quiescence start DNA synthesis at 12 h and reach a maximum at 20 h. The expression of PCNA parallels the synthesis of DNA, Progression through the S phase was inhibited by addition of the anticalmodulin drug W13 to the cells during G1, 5 h after activation. W13 also inhibited the increase in both PCNA protein and mRNA indicating that calmodulin regulates its expression, Using TK(-)ts13 cells transfected with a plasmid containing the thymidine kinase gene under the control of the human 2.8 kb PCNA promoter, we demonstrated that this promoter is not regulated by calmodulin. The half-life of PCNA mRNA during G1/S transition was not modified by the treatment with W13, indicating that the decrease in the mRMA found when calmodulin was inhibited is not due to changes in its stability. Run-on assays revealed that control cells produced predominantly complete PCNA transcripts during S phase, while short incomplete transcripts were generated in W13-treated cells at the same time. These results indicate that calmodulin participates in a more direct or indirect way during G1 in the activation of PCNA expression, From data presented here it can be suggested that calmodulin activates the release of a transcriptional block reading to an increase in the amount of PCNA during S phase.

• 出版日期1995-7