The B subunit of a rat heteromeric CCAAT-binding transcription factor shows a striking sequence identity with the yeast Hap2 transcription factor.
The B subunit of a rat heteromeric CCAAT-binding transcription factor shows a striking sequence identity with the yeast Hap2 transcription factor.
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DOI：
10.1073/pnas.87.14.5378
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发表时间：
1990-07
影响因子：
11.1
通讯作者：
S. Maity;T. Vuorio;B. Crombrugghe
中科院分区：
文献类型：
--
作者：
S. Maity;T. Vuorio;B. Crombrugghe
CBF是一种异聚体哺乳动物转录因子，其结合许多启动子中的CCAAT序列，如两个I型胶原启动子、白蛋白启动子、主要组织相容性复合体II类启动子等。它由两种成分A和B组成，这两种成分都是DNA结合所需的。我们已经分离出一个大鼠的cDNA包含完整的341个氨基酸的编码序列的B成分的CBF。该cDNA的体外表达产生一种多肽，该多肽在与含CCAAT的DNA形成复合物时显示出与天然B组分相同的对A组分的依赖性。从残基260至残基312的B组分的C末端部分显示与Hap 2蛋白的一部分（酵母中异聚CCAAT结合蛋白的组分）75%的序列同一性。相反，其余的蛋白质显示与Hap2的序列同源性很小，尽管这两种蛋白质都含有富含谷氨酰胺的结构域。在CBF的B组分中，该结构域跨越蛋白质的氨基末端60%，而在Hap 2中，该结构域小得多。因此，在酵母和哺乳动物之间的进化过程中，这种蛋白质的一个结构域中只有少数变化是可以容忍的，而蛋白质的其余部分则分化得更广泛。
CBF is a heteromeric mammalian transcription factor that binds to CCAAT sequences in a number of promoters such as the two type I collagen promoters, the albumin promoter, the major histocompatibility complex class II promoter, and others. It is composed of two components, A and B, that are both needed for DNA binding. We have isolated a rat cDNA containing the complete 341-amino acid coding sequence of the B component of CBF. Expression of this cDNA in vitro generates a polypeptide that shows the same dependency on the A component as the native B component in the formation of a complex with a CCAAT-containing DNA. The C-terminal portion of the B component from residue 260 to residue 312 shows a 75% sequence identity with a portion of the Hap2 protein, a component of a heteromeric CCAAT-binding protein in yeast. In contrast, the rest of the protein shows little sequence homology with Hap2, although both proteins contain glutamine-rich domains. In the B component of CBF this domain spans the amino-terminal 60% of the protein, whereas in Hap2 this domain is much smaller. Hence, only a few changes in one domain of this protein were tolerated during evolution between yeast and mammals, whereas the rest of the protein diverged much more extensively.