Sun X H, Copeland N G, Jenkins N A, Baltimore D
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142.
Mol Cell Biol. 1991 Nov;11(11):5603-11. doi: 10.1128/mcb.11.11.5603-5611.1991.
The DNA binding activities of some basic region and putative helix-loop-helix (bHLH)-containing transcriptional factors can be inhibited by the Id protein. Because Id contains the HLH motif for dimerization but not the basic amino acid region for DNA binding, heterodimers of Id with bHLH transcriptional factors may not bind to DNA. We have isolated and characterized the gene and cDNA clones for a new Id protein, designated Id2. The Id2 protein contains a helix-loop-helix motif similar to that of the previously described Id protein (referred to here as Id1), but the two proteins are different elsewhere. Id1 and Id2 are encoded by two unlinked genes, as shown by chromosome mapping. The two Id proteins have similar inhibitory activities. They selectively bind to and inhibit the function of one set of bHLH proteins, typified by E2A.E47 and E2B.m3, but not that of the other set, including TFE3, USF, and AP4. The Id proteins also homodimerize poorly. Expression of both Id genes is down-regulated during differentiation in a variety of cell types.
某些含有碱性区域和假定的螺旋-环-螺旋（bHLH）结构域的转录因子的DNA结合活性可被Id蛋白抑制。由于Id含有用于二聚化的HLH基序，但不含有用于DNA结合的碱性氨基酸区域，因此Id与bHLH转录因子的异源二聚体可能无法结合DNA。我们已经分离并鉴定了一种新的Id蛋白（命名为Id2）的基因和cDNA克隆。Id2蛋白含有与先前描述的Id蛋白（此处称为Id1）类似的螺旋-环-螺旋基序，但这两种蛋白在其他方面有所不同。如染色体定位所示，Id1和Id2由两个不连锁的基因编码。这两种Id蛋白具有相似的抑制活性。它们选择性地结合并抑制一组以E2A.E47和E2B.m3为代表的bHLH蛋白的功能，但不抑制包括TFE3、USF和AP4在内的另一组bHLH蛋白的功能。Id蛋白自身二聚化的能力也很差。在多种细胞类型的分化过程中，两种Id基因的表达均下调。
