Identification of two forms of the RNA polymerase I transcription factor UBF.
Identification of two forms of the RNA polymerase I transcription factor UBF.
复制标题
鉴定两种形式的 RNA 聚合酶 I 转录因子 UBF。
DOI：
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发表时间：
1991
影响因子：
11.1
通讯作者：
L. Rothblum
中科院分区：
文献类型：
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作者：
Daniel J. O'Mahony;L. Rothblum
研究了RNA聚合酶I转录因子UBF的大鼠同源物的结构。从cDNA文库中分离的重叠cDNA序列和通过随机引物第一链cDNA的聚合酶链反应产生的产物克隆中推导出蛋白质的序列。这些克隆的序列表明，有两个mRNA的UBF和编码的蛋白质是相似的，但不相同。一种形式的大鼠UBF与人UBF基本相同。第二类UBF mRNA在编码区含有框内“缺失”，导致从预测的蛋白质序列中缺失37个氨基酸。这种缺失使UBF编码形式的预测分子大小从89.4 kDa减少到85 kDa，减少了约4400，并显著改变了该形式UBF中四个HMG-1同源区之一（HMG box-2）的结构。通过探针保护试验证实了大鼠细胞中存在两种mRNA的证据，并且我们提供了其他脊椎动物细胞含有这两种相同形式的UBF mRNA的证据。这些结果与从四种不同脊椎动物中纯化的UBF在SDS/PAGE上迁移为两条带的观察结果一致。据推测，HMG基序是UBF的DNA结合结构域。改变这些“盒子”之一，如第二种形式的UBF，可能会改变转录因子的功能特征。因此，不同形式的UBF的存在可能对RNA聚合酶I的转录有重要的影响。
The structure of the rat homologue of the RNA polymerase I transcription factor UBF was investigated. The sequence of the protein was deduced from the sequence of overlapping cDNAs isolated from a cDNA library and from clones of the products generated by the polymerase chain reaction from random-primed, first-strand cDNA. The sequences of these clones indicated that there were two mRNAs for UBF and that the encoded proteins were similar but not identical. One form of rat UBF was essentially identical to human UBF. The second class of UBF mRNA contained an in-frame "deletion" in the coding region that results in the deletion of 37 amino acids from the predicted protein sequence. This deletion reduces the predicted molecular size of the encoded form of UBF by approximately 4400 from 89.4 kDa to 85 kDa and significantly alters the structure of one of the four HMG-1 homology regions (HMG box-2) in that form of UBF. Evidence for the existence of two mRNAs in rat cells was confirmed by a probe protection assay, and we provide evidence that other vertebrate cells contain these same two forms of UBF mRNA. These results are consistent with the observation that UBF purified from four different vertebrates migrates as two bands upon SDS/PAGE. It has been hypothesized that the HMG motifs are the DNA-binding domains of UBF. Altering one of these "boxes," as in the second form of UBF, may alter the functional characteristics of the transcription factor. Thus, the existence of different forms of UBF may have important ramifications for transcription by RNA polymerase I.