Goldman G H, Morris N R
University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Department of Pharmacology, Piscataway 08854-5635, USA.
Genetics. 1995 Mar;139(3):1223-32. doi: 10.1093/genetics/139.3.1223.
Cytoplasmic dynein is a large molecular weight protein complex that functions as a microtubule-dependent, negative, end-directed "motor." Mutations in nudA, which encodes the heavy chain of cytoplasmic dynein, inhibit nuclear migration in Aspergillus nidulans. This paper describes the selection and characterization of extragenic suppressors of the nudA1 mutation preparatory to the identification of other proteins that interact directly or indirectly with the cytoplasmic dynein heavy chain. To facilitate future cloning of the suppressor genes, we have searched particularly for extragenic suppressor mutations that also convey a selectable phenotype, such as cold or dimethyl sulfoxide sensitivity. Genetic analysis of 16 revertants has defined at least five extragenic suppressors of nudA1 (snaA-E). All the sna mutations except one were recessive in diploids homozygous for nudA1 and heterozygous for sna mutations. To characterize the nuclear migration phenotype in the sna mutants, conidia of one representative of each complementation group were germinated, fixed and nuclei stained. The sna mutants display partial suppression of the nudA1 nuclear migration defect. Although conidiophores were produced in the sna mutants, they failed to develop normally and to produce spores. Examination of the nudA1,sna conidiophores under the microscope showed that nuclear migration into the metulae and phialides was defective.
细胞质动力蛋白是一种大分子量蛋白质复合物，作为一种依赖微管的、负向的、末端定向的“马达”发挥作用。编码细胞质动力蛋白重链的nudA基因突变会抑制构巢曲霉中的核迁移。本文描述了nudA1突变的基因外抑制子的筛选和特征分析，为鉴定与细胞质动力蛋白重链直接或间接相互作用的其他蛋白质做准备。为便于将来克隆抑制基因，我们特别寻找了也能传递可选择表型（如对冷或二甲基亚砜敏感）的基因外抑制突变。对16个回复突变体的遗传分析确定了nudA1的至少5个基因外抑制子（snaA - E）。除一个之外，所有sna突变在nudA1纯合且sna突变杂合的二倍体中都是隐性的。为了表征sna突变体中的核迁移表型，将每个互补组的一个代表性菌株的分生孢子萌发、固定并对细胞核进行染色。sna突变体表现出对nudA1核迁移缺陷的部分抑制。虽然在sna突变体中产生了分生孢子梗，但它们未能正常发育并产生孢子。在显微镜下检查nudA1、sna分生孢子梗发现，核迁移到梗基和小梗中存在缺陷。
