Abstract
Metallothionein (MT) is a small molecule that regulates the intracellular metal homeostasis. In the early researches, MT was found to be linked to cell proliferation and its expression is cell cycle-dependent. In the present study, we investigated the correlation between cell cycle and the expression of MTF-1 (metal-regulatory transcription factor-1), which regulates MT gene transcription. We established a cell line stably expressing His-tagged MTF-1 in CHO-K1 cells. By using 50 ng/ml colcemid or 0.1 μg/ml nocodazole to arrest cells at metaphase, we observed a modification of MTF-1, which is proved to be phosphorylation. When combining serum depletion and aphidicolin treatment to arrest cells at G1/S boundary, followed by synchronously progression, phosphorylation of MTF-1 around the G2/M phase can be observed. Several kinase inhibitors were used to examine the possible involvement of kinase cascades in the mitotic phosphorylation of MTF-1. The p38, extracellular signal-activated protein kinase (ERK) and the c-Jun N-terminal kinase (JNK) cascades did not appear to be involved in the mitotic phosphorylation of MTF-1. The phosphorylation level was decreased with the co-treatment of colcemid and Cdk1 inhibitor (roscovitine). However, no direct interaction between Cdk1 and MTF-1 can be found as demonstrated by immunoprecipitation assay. These results suggest a link between mitosis and the phosphorylation of MTF-1.