Nucleolin is one component of the B cell-specific transcription factor and switch region binding protein, LR1
Nucleolin is one component of the B cell-specific transcription factor and switch region binding protein, LR1
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DOI：
10.1073/pnas.94.8.3605
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发表时间：
1997-04-15
影响因子：
11.1
通讯作者：
Maizels, N
中科院分区：
文献类型：
--
作者：
Hanakahi, LA;Dempsey, LA;Maizels, N
LR 1是一种B细胞特异性、序列特异性DNA结合活性，可调节活化B细胞中的转录。LR 1还结合IG重链转换区序列，并可能在类别转换重组中起作用。LR 1包含两个多肽，106 kDa和45 kDa，在这里，我们报告说，106 kDa的LR 1组件是核仁素。这种鉴定最初是通过微序列分析进行的，通过显示（i）在用核仁素cDNA表达构建体转染的B细胞中LR 1-DNA结合活性增加;（ii）LR 1-DNA结合活性被针对重组人核仁素产生的抗体识别;和（iii）在用表位标记的核仁素表达构建体转染的B细胞中，LR 1-DNA复合物被抗标记抗体识别。核仁素是一种含量丰富的核仁蛋白，被认为在rDNA转录或组织或rRNA加工中起作用。核仁素和组蛋白H1之间的同源性表明，核仁素可能会改变DNA的组织响应细胞周期的控制，和核仁素LR 1的组成部分，因此可能会发挥作用，组织开关区域之前，期间，或之后开关重组。核仁素是结合开关区序列的B细胞特异性复合物的一个组分，这一证明表明富含G的开关区可能是从rDNA进化而来的。
LR1 is a B cell-specific, sequence-specific DNA binding activity that regulates transcription in activated B cells. LR1 also binds Ig heavy chain switch region sequences and may function in class switch recombination. LR1 contains two polypeptides, of 106 kDa and 45 kDa, and here we report that the 106-kDa component of LR1 is nucleolin. This identification, initially made by microsequence analysis, was verified by showing that (i) LR1-DNA binding activity increased in B cells transfected with a nucleolin cDNA expression construct; (ii) LR1-DNA binding activity was recognized by antibodies raised against recombinant human nucleolin; and (iii) in B cells transfected with epitope-tagged nucleolin expression constructs, the LR1-DNA complex was recognized by the anti-tag antibody. Nucleolin is an abundant nucleolar protein which is believed to play a role in rDNA transcription or organization, or rRNA processing. Homology between nucleolin and histone H1 suggests that nucleolin may alter DNA organization in response to cell cycle controls, and the nucleolin component of LR1 may therefore function to organize switch regions before, during, or after switch recombination. The demonstration that nucleolin is a component of a B cell-specific complex that binds switch region sequences suggests that the G-rich switch regions may have evolved from rDNA.