Liu Wei-Jun, Zhang Yong-Wei, Zhang Zhi-Xiang, Ding Jian
Division of Anti-tumor Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 201203, China.
J Pharmacol Sci. 2004 Oct;96(2):106-14. doi: 10.1254/jphs.fp0030600. Epub 2004 Oct 2.
Alternative splicing of the human telomerase reverse transcriptase subunit (hTERT) suppresses telomerase activity during the development of human fetal kidney cells into mature cells. Tumor cell differentiation is the process of turning abnormal tumor cells into 'normal' cells accompanied by down-regulation of telomerase activity. However, the precise mechanism of the regulation of telomerase activity in differentiated cells is not fully understood. In this study, we observed the role of alternative splicing of hTERT in the regulation of telomerase activity in all-trans-retinoic acid (ATRA)-induced, differentiated HL-60 cells. ATRA-induced down-regulation of telomerase activity in differentiated HL-60 cells was associated with a decrease in hTERT and an increase in human telomerase-associated protein-1 (hTP1) transcription. Expression of full length variant hTERT alpha+ beta+ mRNA decreased in a dose- and time-dependent manner. The drop of hTERT beta- mRNA was time-dependent. hTERT alpha- and hTERT alpha- beta- mRNA were reduced dramatically after ATRA treatment. In the dose-effect study, hTERT alpha+ beta+ and hTERT beta- maintained a relatively stable ratio when telomerase activity decreased largely from treatment with 1 to 5 microM ATRA. Although the splicing pattern of hTERT mRNA was altered in time-effect research, the change was not related to the ATRA-treated decline of telomerase activity. The expression of alternative splicing variants of hTERT also decreased at the protein level. All these results suggested that alternative splicing of hTERT mRNA may not contribute to the suppression of telomerase activity during ATRA-induced HL-60 leukemia cell differentiation.
人端粒酶逆转录酶亚基（hTERT）的可变剪接在人胎儿肾细胞发育为成熟细胞的过程中抑制端粒酶活性。肿瘤细胞分化是将异常肿瘤细胞转变为“正常”细胞的过程，同时伴随着端粒酶活性的下调。然而，分化细胞中端粒酶活性调控的确切机制尚未完全明确。在本研究中，我们观察了hTERT可变剪接在全反式维甲酸（ATRA）诱导分化的HL-60细胞中端粒酶活性调控中的作用。ATRA诱导HL-60分化细胞中端粒酶活性下调与hTERT减少及人端粒酶相关蛋白-1（hTP1）转录增加有关。全长变异体hTERTα+β+mRNA的表达呈剂量和时间依赖性降低。hTERTβ-mRNA的下降呈时间依赖性。ATRA处理后，hTERTα-和hTERTα-β-mRNA显著减少。在剂量效应研究中，当端粒酶活性因1至5μM ATRA处理而大幅下降时，hTERTα+β+和hTERTβ-保持相对稳定的比例。尽管在时间效应研究中hTERT mRNA的剪接模式发生了改变，但这种变化与ATRA处理后端粒酶活性的下降无关。hTERT可变剪接变体的表达在蛋白水平也降低。所有这些结果表明，hTERT mRNA的可变剪接可能在ATRA诱导的HL-60白血病细胞分化过程中对端粒酶活性的抑制作用不大。
