Post-transcriptional regulation of H-ferritin gene expression in human monocytic THP-1 cells by protein kinase C.
The mRNA coding for H-ferritin was highly induced in human monocytic THP-1 cells following treatment with phorbol 12-myristate 13-acetate (PMA). The induction was detected at 3 h, reached maximal levels at 12 h, and was sustained for up to 48 h subsequent to PMA exposure. PMA-induced up-regulation of H-ferritin gene expression was also observed in other leukaemic cell lines, HL60 and U937, but not in non-leukaemic cell types, including human fibroblasts, endothelial cells and smooth muscle cells. The effect of PMA could be completely blocked by the protein kinase C inhibitor, H-7. Furthermore, treatment of THP-1 cells with bacterial phospholipase C also produced a marked increase in expression of H-ferritin mRNA, suggesting the activation of protein kinase C was responsible for the accumulation of mRNA. Nuclear run-off experiments demonstrated that PMA did not increase the transcriptional rate of the H-ferritin gene. In contrast, the half-life of the H-ferritin mRNA measured in the presence of actinomycin D was greatly prolonged in PMA-treated cells. The induction of H-ferritin mRNA by PMA required no protein synthesis. Conversely, treatment of THP-J cells with protein synthesis inhibitor, cycloheximide, resulted in a 4-5-fold increase in H-ferritin mRNA. The increase in the stability of the H-ferritin mRNA was also observed in cells treated with cycloheximide. Taken together, these results suggest that the stability of H-ferritin mRNA in THP-1 is subjected to regulation via a protein kinase C-mediated phosphorylation on existing putative protein factor(s).
Pang
J H
JH
Division of Cardiovascular Research, Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei, Taiwan, R.O.C.
Wu
C J
CJ
Chau
L Y
LY
D002454:Cell Differentiation; D003513:Cycloheximide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005293:Ferritins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D006207:Half-Life; D006801:Humans; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D005293:Ferritins; D003513:Cycloheximide; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate