Grassilli E, Salomoni P, Perrotti D, Franceschi C, Calabretta B
Department of Microbiology and Immunology and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Cancer Res. 1999 May 15;59(10):2451-6.
Transcriptional regulators of the Myb family play important roles in cell proliferation, differentiation, and survival. To investigate the role of Myb proteins in the regulation of apoptosis, we studied the apoptotic response of interleukin 2-dependent CTLL-2 cells stably transfected with B-Myb. B-Myb-overexpressing cells showed a diminished cytokine dependence and were resistant to apoptosis induced by doxorubicin, ceramide, and dexamethasone. Overexpression of B-Myb was associated with enhanced expression of bcl-2, which was dependent, at least in part, on increased transcription. In transient transfection assays in T-lymphoblastic cells, B-Myb was able to stimulate the promoter activity of the bcl-2 5' flanking region linked to the chloramphenicol acetyltransferase reporter gene. A segment of the bcl-2 promoter (nucleotides +34 to +58 relative to the transcription initiation site) contained a putative Myb-binding site and was shown to specifically interact with B-Myb and to confer B-Myb responsiveness to a bcl-2/chloramphenicol acetyltransferase reporter construct. These results indicate that B-Myb promotes T cells survival by enhancing the expression of bcl-2 and identify bcl-2 as a B-Myb target gene regulated in a DNA binding-dependent manner.
Myb家族的转录调节因子在细胞增殖、分化和存活中发挥着重要作用。为了研究Myb蛋白在细胞凋亡调控中的作用，我们研究了稳定转染B-Myb的白细胞介素2依赖的CTLL-2细胞的凋亡反应。过表达B-Myb的细胞表现出细胞因子依赖性降低，并对阿霉素、神经酰胺和地塞米松诱导的凋亡具有抗性。B-Myb的过表达与bcl-2表达增强有关，这至少部分依赖于转录增加。在T淋巴细胞母细胞的瞬时转染试验中，B-Myb能够刺激与氯霉素乙酰转移酶报告基因相连的bcl-2 5'侧翼区域的启动子活性。bcl-2启动子的一段（相对于转录起始位点的核苷酸+34至+58）包含一个假定的Myb结合位点，并显示与B-Myb特异性相互作用，并赋予bcl-2/氯霉素乙酰转移酶报告构建体对B-Myb的反应性。这些结果表明，B-Myb通过增强bcl-2的表达促进T细胞存活，并将bcl-2鉴定为以DNA结合依赖方式调控的B-Myb靶基因。
