Effects of methylation status of CpG islands on results of luciferase reporter assay / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of methylation status of CpG islands of endogenous E-cadherin (CDH1) gene on the promoter activity of corresponding genes in reporter assays.</p><p><b>METHODS</b>The methylation statuses of CpG island of CDH1 in 8 different cell lines were detected by methylation-specific PCR. CDH1 protein was analyzed by Western blotting. Two sets of pGL3 reporter vectors with different genotypes/haplotypes of the CDH1 promoter were constructed [ pGL3-A(-73)/-C(-73) pGL3-H1/-H4] and used to transfect these cell lines. The differences between these promoter reporter vectors were analyzed by t-test.</p><p><b>RESULTS</b>(1) CDH1 CpG island was unmethylated in AGS, MCF7, MKN74, and PC-3 cell lines, expressed in MCF7, MKN74, and PC-3, but not in AGS. Expression of CDH1 was silenced by methylation in HeLa, BGC823, A549, and RKO cell lines. (2) In the four CDH1-unmethylated MCF7, MKN74, PC-3, and AGS cell lines, the promoter activities of pGL3-C(-73), (as 0.78 +/- 0.10, 0.17 +/- 0.01, 0.11 +/- 0.01, 1.19 +/- 0.18) were significantly higher than those of pGL3-A(-73) (as 0.30 +/- 0.08, 0.07 +/- 0.01, 0.07 +/- 0.01, 0.39 +/- 0.04) (t values are -6.298, - 12.349, -8.128, -7.388, and P <. 0.1). However, in the four CDH1-methylated HeLa, BGC823, A549, and RKO cell lines, the promoter activity of pGL3-C(-73) (as 0.09 +/- 0.02, 0.13 +/- 0.02, 0.05 +/- 0.01, 0.01 +/- 0.00) was significantly lower than that of pGL3-A(-73) (as 0.16 +/- 0.01, 0.25 +/- 0.01, 0.11 +/- 0.03, 0.03 +/- 0.00) (t valued at 5.958, 11.189, 3.661, 13.866, and P<0.05). (3) In the unmethylated MKN74 and methylated RKO cell lines, the promoter activities of pGL3-H1/-H4 were obviously and contrarily different (as 1.57 +/- 0.23/0.94 +/- 0.06 and 0.38 +/- 0.02/0.50 +/- 0.04, t values were 4.577 and -4.915, P values were 0.010 and 0.003).</p><p><b>CONCLUSION</b>The methylation status of CpG island of the target gene in the tested cell lines affects the promoter activity in Reporter Assay significantly. The most active one may be the most suppressive one.</p>

STI571 induces apoptosis of K562 cells through down-regulation of anti-apoptotic protein Mcl-1 and Bcl-xl expression / 中国实验血液学杂志

This study was aimed to investigate the effect of STI571, an inhibitor of tyrosine kinase, on the proliferation and apoptosis of chronic myelogenous leukemia (CML) cells as well as expression of anti-apoptotic protein Mcl-1, and to explore the possible role of Mcl-1 in apoptosis-inducing mechanism. K562 cell line was used to observe the effect of STI571 on CML cells. Proliferation and cytotoxicity were analyzed by MTT assay. The apoptotic cells were labelled with Annexin V-FITC and PI and then analyzed by flow cytometry. The expression of apoptotic-related proteins in K562 cells was determined by Western blot with specific antibodies. The results showed that STI571 significantly inhibited the proliferation and induced apoptosis of K562 cells in a dose-and time-dependent manner. Coincidently, the protein phosphorylation on tyrosine residues was reduced and the expressions of anti-apoptotic protein Mcl-1 and Bcl-xl were down-regulated after exposure to STI571. It is concluded that STI571 induces the apoptosis of CML cells by down-regulating the expressions of Mcl-1 and Bcl-xl, which suggests that Mcl-1 and Bcl-xl may play an important role in anti-apoptotic process of CML cells.

Methylation specific binding activity of zinc finger protein Kaiso / 中华预防医学杂志

<p><b>OBJECTIVE</b>To compare binding activity of different zinc finger domain of human Kaiso with methylated CpG.</p><p><b>METHODS</b>pGEX constructs with different human Kaiso domain were generated and then corresponding fusion proteins were induced and purified. Electrophoretic mobility shift assays were applied to evaluate the binding activity of fusion proteins with methylated CpG.</p><p><b>RESULTS</b>The purified GST-KaisoZF fusion protein (without the POZ protein binding domain) could bind with methylated CpG probe specifically, but not for three or two zinc fingers without flanking domains.</p><p><b>CONCLUSION</b>Human zinc finger protein Kaiso could bind with methylated CpG specifically, only in the assistance of the neighboring flank sequence of the zinc finger domain.</p>