Dowzer C E, Kelly J M
Department of Genetics, University of Adelaide, Australia.
Mol Cell Biol. 1991 Nov;11(11):5701-9. doi: 10.1128/mcb.11.11.5701-5709.1991.
The complete nucleotide sequence derived from a genomic clone and two cDNA clones of the creA gene of Aspergillus nidulans is presented. The gene contains no introns. The derived polypeptide of 415 amino acids contains two zinc fingers of the C2H2 class, frequent S(T)PXX motifs, and an alanine-rich region indicative of a DNA-binding repressor protein. The amino acid sequence of the zinc finger region has 84% similarity to the zinc finger region of Mig1, a protein involved in carbon catabolite repression in yeast cells, and it is related both to the mammalian Egr1 and Egr2 proteins and to the Wilms' tumor protein. A deletion removing the creA gene was obtained, by using in vitro techniques, in both a heterokaryon and a diploid strain but was unobtainable in a pure haploid condition. Evidence is presented suggesting that the phenotype of such a deletion, when not complemented by another creA allele, is leaky lethality allowing limited germination of the spore but not colony formation. This phenotype is far more extreme than that of any of the in vivo-generated mutations, and thus either the gene product may have an activator activity as well as a repressor function or some residual repressor function may be required for full viability.
本文给出了构巢曲霉creA基因的一个基因组克隆和两个cDNA克隆的完整核苷酸序列。该基因不含内含子。推导的由415个氨基酸组成的多肽含有两个C2H2类锌指结构、常见的S(T)PXX基序以及一个富含丙氨酸的区域，表明这是一种DNA结合阻遏蛋白。锌指区域的氨基酸序列与Mig1的锌指区域有84%的相似性，Mig1是一种参与酵母细胞碳源分解代谢阻遏的蛋白质，它与哺乳动物的Egr1和Egr2蛋白以及威尔姆斯瘤蛋白都有关系。通过体外技术，在异核体和二倍体菌株中都获得了缺失creA基因的菌株，但在纯单倍体条件下无法获得。有证据表明，当这种缺失的表型没有被另一个creA等位基因互补时，其表型是渗漏致死性，允许孢子有限萌发但不能形成菌落。这种表型比任何体内产生的突变都要极端得多，因此要么该基因产物可能同时具有激活剂活性和阻遏功能，要么可能需要一些残余的阻遏功能才能实现完全存活。
