Barrett P, Sommerville J
Department of Biology, University of St Andrews, Fife, UK.
Nucleic Acids Res. 1987 Nov 11;15(21):8679-91. doi: 10.1093/nar/15.21.8679.
In small oocytes of Xenopus species, two sets of 5S RNA genes, oocyte-type and somatic-type, are fully activated. The 5S RNA transcripts are temporarily stored, half in association with TFIIIA to form a 7S particle, the other half in association with tRNA and two proteins (p48 and p43) to form a 42S particle. It has been established previously that TFIIIA binds to the internal control region of 5S RNA genes and promotes their transcription. Here we show that protein can be translocated from the 42S particles to 5S RNA genes, but only after treatment of the particles with ribonuclease. Nevertheless, once transferred, stable protein-DNA complexes are formed and DNase-protection experiments show that binding is specific to the gene promoter, covering exactly the same sequence as TFIIIA. The DNA-binding protein is identified as p48 which, after isolation by ion-exchange chromatography, will bind to 5S RNA genes in the absence of ribonuclease.
在非洲爪蟾属物种的小卵母细胞中，两组5S RNA基因，即卵母细胞型和体细胞型，均被完全激活。5S RNA转录本被暂时储存，一半与TFIIIA结合形成7S颗粒，另一半与tRNA及两种蛋白质（p48和p43）结合形成42S颗粒。先前已经确定TFIIIA与5S RNA基因的内部控制区结合并促进其转录。在此我们表明，蛋白质可以从42S颗粒转移至5S RNA基因，但前提是先用核糖核酸酶处理颗粒。然而，一旦转移，就会形成稳定的蛋白质 - DNA复合物，并且DNase保护实验表明结合对基因启动子具有特异性，覆盖的序列与TFIIIA完全相同。该DNA结合蛋白被鉴定为p48，经离子交换色谱法分离后，它在没有核糖核酸酶的情况下也能与5S RNA基因结合。
