Pengue G, Lania L
Department of Genetics, Molecular and General Biology, University of Naples, Federico II, Italy.
Proc Natl Acad Sci U S A. 1996 Feb 6;93(3):1015-20. doi: 10.1073/pnas.93.3.1015.
The evolutionarily conserved Krüppel-associated box (KRAB) is present in the N-terminal regions of more than one-third of all Krüppel-class zinc finger proteins. Recent experiments have demonstrated that the KRAB-A domain tethered to a promoter DNA by connecting to heterologous DNA-binding protein domain or targeted to a promoter-proximal RNA sequence acts as a transcriptional silencing of RNA polymerase II promoters. Here we show that expression of KRAB domain suppresses in vivo the activating function of various defined activating transcription factors, and we demonstrate that the KRAB domain specifically silences the activity of promoters whose initiation is dependent on the presence of a TATA box. Promoters whose accurate transcription initiation is directed by a pyrimidine-rich initiator element, however, are relatively unaffected. We also report in vitro transcription experiments indicating that the KRAB domain is able to repress both activated and basal promoter activity. Thus, the KRAB domain appears to repress the activity of certain promoters through direct communication with TATA box-dependent basal transcription machinery.
进化上保守的克虏伯相关框（KRAB）存在于所有克虏伯类锌指蛋白三分之一以上的N端区域。最近的实验表明，通过连接到异源DNA结合蛋白结构域或靶向启动子近端RNA序列而与启动子DNA相连的KRAB-A结构域可作为RNA聚合酶II启动子的转录沉默因子。在此我们表明，KRAB结构域的表达在体内抑制了各种确定的激活转录因子的激活功能，并且我们证明KRAB结构域特异性地沉默了其起始依赖于TATA框存在的启动子的活性。然而，其精确转录起始由富含嘧啶的起始子元件指导的启动子相对不受影响。我们还报告了体外转录实验，表明KRAB结构域能够抑制激活的和基础的启动子活性。因此，KRAB结构域似乎通过与TATA框依赖性基础转录机制的直接通讯来抑制某些启动子的活性。
