Ikaros抑制垂体瘤生长激素基因表达的机制  

Action mechanism of inhibited pituitary growth hormone gene expression by Ikaros

作　　者：于顺江[1] 陈力[1] 陈怡东[1] 王京[2] 

机构地区：[1]北京世纪坛医院(暨北京大学第九临床医学院)肿瘤放疗科,北京100038 [2]北京世纪坛医院(暨北京大学第九临床医学院)病理科,北京100038

出　　处：《中国癌症杂志》2010年第8期566-571,共6页China Oncology

摘　　要：背景与目的:Ikaros(Ik-1)锌指蛋白转录因子在垂体腺体中有表达,也有研究证实Ik-1在淋巴造血系统以及免疫调节过程中起极为重要的作用。本研究旨在探讨Ik-1在调节垂体生长激素(growth hormone,GH)基因表达方面的作用及其机制。方法:以稳定转染的鼠垂体GH4细胞株为研究平台,运用细胞与分子生物学技术如稳定转染、瞬时转染、免疫组化、Northernblot、蛋白质印记法及染色质免疫共沉淀等方法分析Ik-1及其同工蛋白Ik-6在垂体GH基因表达调节中的作用机制。结果:通过RNA和蛋白质印记分析,证实野生型Ik-1抑制了GH基因的mRNA和蛋白水平的表达,这一抑制作用不是由于Ik-1直接与GH基因启动子DNA结合,而是因为Ik-1选择性地加重了GH基因启动子区域的组蛋白去乙酰化状态,从而阻碍了Pit1与GH基因启动子DNA的结合,导致了GH基因表达的抑制。结论:Ik-1抑制GH基因表达是通过阻抑Pit1与GH基因启动子结合来实现的。这一研究将为激素过度分泌的功能性垂体腺瘤的临床分子靶向治疗提供新的视野。Background and purpose：The Ikaros transcription factors play critical roles in the control of lympho-hematopoiesis and immune regulation. Ikaros contains multiple zinc fingers that mediate DNA binding and has also been implicated in the regulation of some key genes in the development of hematopoiesis. It was demonstrated that Ikaros can be expressed in the pituitary. This study was to investigate action mechanism of the transcription factor Ikaros in the regulations of GH gene expression in the pituitary. Methods：By using stable or transient transfected mouse GH4 cell line, we utilized various cell and molecular biological techniques including cell transfection, immunohistochemistry （IHC）, Northern blot, Western blot analysis, ChIP-PCR assay, etc. to examine the expression of Ikaros in GH4 cells, and to observe exogenous expressed Ikaros, its isoform Ik-6 and its impact on expression of the GH gene. Results：Northern and Western blot analysis revealed that Wild-type Ikaros （Ik-1） inhibited mRNA and protein expression of the GH gene in GH4 cells. Ikaros didn’t bind directly to the proximal GH promoter but could abrogate the acetylated effect of the histone deacetylation inhibitor Trichostatin-A on this region. Through deacetylation of the histone-3 residues on the proximal GH promoter, Ik-1 inhibited selectively the expression of the GH genes and limited access of the activator- Pit1 to bind with the GH promoter. Conclusion：These data showed evidence for Ikaros-mediated histone deacetylation as well as chromatin remodeling in the selective inhibition of pituitary GH gene expression, and provided a clinically insight for molecular targeted design against functional hormone over-secreted pituitary adenomas in the future.

关 键 词：Ikaros基因 基因表达 垂体腺瘤 生长激素 

分 类 号：R730.22[医药卫生—肿瘤] R739.41[医药卫生—临床医学]