Hibiya Y
Department of Biochemistry, Hokkaido University School of Medicine, Sapporo, Japan.
Hokkaido Igaku Zasshi. 1997 Jan;72(1):69-83.
The v-maf oncogene, originally identified as the transforming gene of the avian retrovirus AS42, encodes a protein with a basic-leucine zipper (bZIP) structure which is a typical motif for protein dimerization and DNA binding. The v-Maf protein forms homodimers and sometimes heterodimers with some bZIP proteins and works as a transcription factor. Recent studies of tissue-specific expression of cellular Maf family proteins suggest that Maf-related proteins play important roles in early development and cell differentiation. In our previous studies, two maf-related cDNA clones, maf-1 and maf-2, have been isolated from a rat liver cDNA library which facilitates the investigation of physiological roles of Mafs as well as their target genes in mammals. We determine here the binding DNA sequences of Maf-1 and Maf-2, respectively. Maf-1 recognizes a number of sequences containing a short consensus sequence, -GCTGAC-, half of the Maf recognition element (MARE) which has been previously identified for V-Maf. On the other hand, binding sequences of Maf-2 are limited and Maf-2 binds to the MARE preferentially. It is shown that dimer-forming specificities of Maf-1 and Maf-2 to Jun or Fos family proteins are variable. Maf-1 efficiently forms heterodimers with Fos family proteins. Compared to the case of Maf-2, though the DNA-binding specificity of the heterodimer depends on the kind of counterpart binding to Maf-1, a wide variety of target sequences are available for Maf-1. In contrast, Maf-2 shows restricted heterodimer-forming specificity and DNA-binding specificity, so that the target genes for Maf-2 are considered to be much more limited.
v-maf癌基因最初被鉴定为禽逆转录病毒AS42的转化基因，编码一种具有碱性亮氨酸拉链（bZIP）结构的蛋白质，该结构是蛋白质二聚化和DNA结合的典型基序。v-Maf蛋白形成同二聚体，有时与一些bZIP蛋白形成异二聚体，并作为转录因子发挥作用。最近对细胞Maf家族蛋白组织特异性表达的研究表明，Maf相关蛋白在早期发育和细胞分化中起重要作用。在我们之前的研究中，从大鼠肝脏cDNA文库中分离出两个与maf相关的cDNA克隆，maf-1和maf-2，这有助于研究Mafs及其在哺乳动物中的靶基因的生理作用。我们在此分别确定了Maf-1和Maf-2的结合DNA序列。Maf-1识别许多含有短共有序列-GCTGAC-的序列，这是先前为V-Maf鉴定的Maf识别元件（MARE）的一半。另一方面，Maf-2的结合序列有限，且Maf-2优先结合MARE。结果表明，Maf-1和Maf-2与Jun或Fos家族蛋白形成二聚体的特异性是可变的。Maf-1能有效地与Fos家族蛋白形成异二聚体。与Maf-2的情况相比，虽然异二聚体的DNA结合特异性取决于与Maf-1结合的对应物的种类，但Maf-1有多种靶序列可供选择。相反，Maf-2显示出有限的异二聚体形成特异性和DNA结合特异性，因此Maf-2的靶基因被认为要少得多。
