Altered expression of nuclear matrix proteins in etoposide induced apoptosis in HL-60 cells

JIN Mei Lin^1,*, Ping ZHANG³, Ming Xiao DING², Jing Ping YUN³, Pei Fang CHEN³, Yeuk Hon CHEN³, Yin Qing CHEW³

¹College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China
²College of Life Sciences, Beijing University, Beijing 100871, China
³Chinese University of Hong Kong, Hong Kong, China

The events of cell death and the expression of nuclear matrix protein (NMP) have been investigated in a promyelocytic leukemic cell line HL-60 induced with etoposide. By means of TUNEL assay, the nuclei displayed a characteristic morphology change, and the amount of apoptotic cells increased early and reached maximun about 39% after treatment with etoposide for 2 h. Nucleosomal DNA fragmentation was observed after treatment for 4 h. The morphological change of HL-60 cells, thus, occurred earlier than the appearance of DNA ladder. Total nuclear matrix proteins were analyzed by 2-dimensional gel electrophoresis. Differential expression of 59 nuclear matrix proteins was found in 4 h etoposide treated cells. Western blotting was then performed on three nuclear matrix acssociated proteins, PML, HSC70 and NuMA. The expression of the suppressor PML protein and heat shock protein HSC70 were significantly upregulated after etoposide treatment, while NuMA, a nuclear mitotic apparatus protein, was down regulated. These results demonstrate that significant biochemical alterations in nuclear matrix proteins take place during the apoptotic process.