Dörfler P, Busslinger M
Research Institute of Molecular Pathology, Vienna, Austria.
EMBO J. 1996 Apr 15;15(8):1971-82.
Pax-5 encodes the transcription factor BSAP which plays an essential role in early B cell development and midbrain patterning. In this study we have analysed the structural requirements for transcriptional activation by BSAP. In vitro mutagenesis and transient transfection experiments indicate that the C-terminal serine/threonine/proline-rich region of BSAP contains a potent transactivation domain of 55 amino acids which is active from promoter and enhancer positions. This transactivation domain was found to be inactivated by a naturally occurring frameshift mutation in one PAX-5 allele of the acute lymphoblastic leukemia cell line REH. The function of the transactivation domain is negatively regulated by adjacent sequences from the extreme C-terminus. The activating and inhibitory domains function together as an independent regulatory module in different cell types as shown by fusion to the GAL4 DNA binding domain. The same arrangement of positively and negatively acting sequences has been conserved in the mammalian Pax-2 and Pax-8, the zebrafish Pax-b as well as the sea urchin Pax-258 proteins. These data demonstrate that the transcriptional competence of a subfamily of Pax proteins is determined by a C-terminal regulatory module composed of activating and inhibitory sequences.
Pax-5编码转录因子BSAP，其在早期B细胞发育和中脑模式形成中起关键作用。在本研究中，我们分析了BSAP转录激活的结构要求。体外诱变和瞬时转染实验表明，BSAP的C末端富含丝氨酸/苏氨酸/脯氨酸区域包含一个由55个氨基酸组成的强效反式激活结构域，该结构域在启动子和增强子位置均具有活性。发现该反式激活结构域在急性淋巴细胞白血病细胞系REH的一个PAX-5等位基因中因自然发生的移码突变而失活。反式激活结构域的功能受到来自极端C末端的相邻序列的负调控。如与GAL4 DNA结合结构域融合所示，激活和抑制结构域在不同细胞类型中作为一个独立的调节模块共同发挥作用。在哺乳动物Pax-2和Pax-8、斑马鱼Pax-b以及海胆Pax-258蛋白中，正向和负向作用序列的相同排列得以保留。这些数据表明，Pax蛋白亚家族的转录能力由一个由激活和抑制序列组成的C末端调节模块决定。
