Clerc R G, Corcoran L M, LeBowitz J H, Baltimore D, Sharp P A
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
Genes Dev. 1988 Dec;2(12A):1570-81. doi: 10.1101/gad.2.12a.1570.
Transcription of promoters of immunoglobulin genes is controlled by an octanucleotide sequence element. The sequence of a cDNA encoding a B-cell-specific protein, Oct-2, has been determined. This protein specifically recognizes the octanucleotide element and is part of the previously identified NF-A2 family of proteins. The DNA-binding domain of Oct-2 is structurally related to the homeo box consensus and thus contains a potential helix-turn-helix sequence. Oct-2 also possesses a potential 'leucine zipper' domain, where four leucines are each separated by exactly seven residues. Comparisons of Oct-2 with protein Oct-1, which also recognizes the octanucleotide element but is constitutively expressed in all cell types, show high sequence conservation through the 60-residue DNA-binding domain, as well as an adjacent tract of 75 residues. The latter conserved region is also found in regulatory genes expressed in pituitary cells and nematodes and has been termed a POU box. Because two different cDNAs were isolated, it is proposed that the oct-2 gene is expressed as multiple mRNAs that vary in splicing patterns. Most interestingly, the oct-2 cDNA contains a second overlapping open reading frame, 278 residues in length, which might also specify a protein important for B-cell development.
免疫球蛋白基因启动子的转录受一个八核苷酸序列元件的控制。编码一种B细胞特异性蛋白Oct-2的cDNA序列已被确定。这种蛋白能特异性识别八核苷酸元件，并且是先前鉴定的NF-A2蛋白家族的一部分。Oct-2的DNA结合结构域在结构上与同源异型框共有序列相关，因此包含一个潜在的螺旋-转角-螺旋序列。Oct-2还具有一个潜在的“亮氨酸拉链”结构域，其中四个亮氨酸彼此之间恰好间隔七个残基。将Oct-2与同样能识别八核苷酸元件但在所有细胞类型中组成性表达的Oct-1蛋白进行比较，结果显示在60个残基的DNA结合结构域以及相邻的75个残基区域具有高度的序列保守性。后一个保守区域也存在于垂体细胞和线虫中表达的调控基因中，被称为POU框。由于分离出了两种不同的cDNA，因此推测oct-2基因以多种可变剪接模式的mRNA形式表达。最有趣的是，oct-2 cDNA包含一个长度为278个残基的第二个重叠开放阅读框，它可能也编码一种对B细胞发育很重要的蛋白。
