THE BLOCK TO TRANSCRIPTIONAL ELONGATION WITHIN THE HUMAN C-MYC GENE IS DETERMINED IN THE PROMOTER - PROXIMAL REGION
THE BLOCK TO TRANSCRIPTIONAL ELONGATION WITHIN THE HUMAN C-MYC GENE IS DETERMINED IN THE PROMOTER - PROXIMAL REGION
复制标题
DOI：
10.1101/gad.6.11.2201
复制
发表时间：
1992-11-01
影响因子：
10.5
通讯作者：
GROUDINE, M
中科院分区：
文献类型：
--
作者：
KRUMM, A;MEULIA, T;GROUDINE, M
条件阻断转录延伸是调控c-myc基因表达的重要机制。这个位于第一个c-myc外显子内的延伸区最初是在哺乳动物细胞中通过核运行转录分析确定的。随后的卵母细胞注射和体外转录分析表明，第一个c-myc外显子末端附近的序列是衰减和/或过早终止的位点。我们在此报告，用高锰酸钾（KMnO4）在体内绘制单链DNA图谱和核运行转录分析显示，聚合酶在相对于主要c-myc转录起始位点的+30位置附近暂停。在卵母细胞注射和体外转录试验中，删除350 bp，包括3'端形成和固有终止的位点，不会影响启动子近端区域聚合酶的暂停。此外，+47上游的序列足以使聚合酶的启动子-近端暂停，并在下游产生转录极性。因此，RNA聚合酶II复合物的启动子-近端暂停是哺乳动物细胞中c-myc基因延伸受阻的原因。我们推测，聚合酶复合物在启动子-近端暂停位点的修饰可能决定了聚合酶是否可以读取下游更远的内在终止位点。
A conditional block to transcriptional elongation is an important mechanism for regulating c-myc gene expression. This elongation block within the first c-myc exon was defined originally in mammalian cells by nuclear run-on transcription analyses. Subsequent oocyte injection and in vitro transcription analyses suggested that sequences near the end of the first c-myc exon are sites of attenuation and/or premature termination. We report here that the mapping of single stranded DNA in vivo with potassium permanganate (KMnO4) and nuclear run-on transcription assays reveal that polymerase is paused near position +30 relative to the major c-myc transcription initiation site. Deletion of 350 bp, including the sites of 3'-end formation and intrinsic termination defined in oocyte injection and in vitro transcription assays does not affect the pausing of polymerase in the promoter-proximal region. In addition, sequences upstream of +47 are sufficient to confer the promoter-proximal pausing of polymerases and to generate the polarity of transcription farther downstream. Thus, the promoter-proximal pausing of RNA polymerase II complexes accounts for the block to elongation within the c-myc gene in mammalian cells. We speculate that modification of polymerase complexes at the promoter-proximal pause site may determine whether polymerases can read through intrinsic sites of termination farther downstream.