Beckwith S M, Roghi C H, Liu B, Ronald Morris N
Department of Pharmacology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
J Cell Biol. 1998 Nov 30;143(5):1239-47. doi: 10.1083/jcb.143.5.1239.
The heavy chain of cytoplasmic dynein is required for nuclear migration in Aspergillus nidulans and other fungi. Here we report on a new gene required for nuclear migration, nudG, which encodes a homologue of the "8-kD" cytoplasmic dynein light chain (CDLC). We demonstrate that the temperature sensitive nudG8 mutation inhibits nuclear migration and growth at restrictive temperature. This mutation also inhibits asexual and sexual sporulation, decreases the intracellular concentration of the nudG CDLC protein and causes the cytoplasmic dynein heavy chain to be absent from the mycelial tip, where it is normally located in wild-type mycelia. Coimmunoprecipitation experiments with antibodies against the cytoplasmic dynein heavy chain (CDHC) and the nudG CDLC demonstrated that some fraction of the cytoplasmic dynein light chain is in a protein complex with the CDHC. Sucrose gradient sedimentation analysis, however, showed that not all of the NUDG protein is complexed with the heavy chain. A double mutant carrying a cytoplasmic dynein heavy chain deletion plus a temperature-sensitive nudG mutation grew no more slowly at restrictive temperature than a strain with only the CDHC deletion. This result demonstrates that the effect of the nudG mutation on nuclear migration and growth is mediated through an interaction with the CDHC rather than with some other molecule (e.g., myosin-V) with which the 8-kD CDLC might theoretically interact.
胞质动力蛋白重链是构巢曲霉和其他真菌核迁移所必需的。在此，我们报道了一个核迁移所需的新基因nudG，它编码“8-kD”胞质动力蛋白轻链（CDLC）的同源物。我们证明，温度敏感型nudG8突变在限制温度下会抑制核迁移和生长。该突变还会抑制无性和有性孢子形成，降低nudG CDLC蛋白的细胞内浓度，并导致胞质动力蛋白重链在菌丝顶端缺失，而在野生型菌丝中它通常位于此处。用针对胞质动力蛋白重链（CDHC）和nudG CDLC的抗体进行的共免疫沉淀实验表明，一部分胞质动力蛋白轻链与CDHC处于蛋白复合物中。然而，蔗糖梯度沉降分析表明，并非所有的NUDG蛋白都与重链复合。携带胞质动力蛋白重链缺失加上温度敏感型nudG突变的双突变体在限制温度下的生长速度并不比仅缺失CDHC的菌株更慢。这一结果表明，nudG突变对核迁移和生长的影响是通过与CDHC相互作用介导的，而不是与理论上8-kD CDLC可能与之相互作用的其他分子（如肌球蛋白-V）相互作用。
