May G, Le Chevanton L, Pukkila P J
Department of Biology and Curriculum in Genetics, University of North Carolina, Chapel Hill 27599-3280.
Genetics. 1991 Jul;128(3):529-38. doi: 10.1093/genetics/128.3.529.
We report here the molecular cloning of the A43 mating type factor from Coprinus cinereus, a basidiomycetous fungus. Our molecular analyses revealed an unexpected source of variation in the A factor. Though genetic studies have demonstrated that A has two subunits, alpha and beta, we located three nonoverlapping fragments in the A43 region that have A factor function following DNA-mediated transformation. The three fragments demonstrate no similarity to one another as judged by restriction enzyme maps and by hybridization on Southern blots. We conclude that the A43 factor is composed of at least three subunits. When strains carrying different A factors are examined by hybridization to the cloned subunits, extensive polymorphism is seen. Both intensity of hybridization and restriction fragment lengths vary between strains. Some strains fail to show any hybridization to a probe. In contrast, other strains from widely separated geographic locations apparently share very similar subunits. From comparative restriction enzyme mapping of A43 and a mutated A43 factor, we inferred that a 12-kb deletion in the A factor was responsible for the constitutive, dominant phenotype of the mutated A factor. The results of transformation experiments support an activator model for the activity of the A factor in regulating the A pathway.
我们在此报告了来自灰盖鬼伞（一种担子菌纲真菌）的A43交配型因子的分子克隆。我们的分子分析揭示了A因子中一个意想不到的变异来源。尽管遗传学研究表明A因子有两个亚基，α和β，但我们在A43区域定位到了三个不重叠的片段，它们在DNA介导的转化后具有A因子功能。根据限制性酶切图谱和Southern杂交判断，这三个片段彼此之间没有相似性。我们得出结论，A43因子至少由三个亚基组成。当通过与克隆的亚基杂交来检测携带不同A因子的菌株时，可以看到广泛的多态性。菌株之间杂交的强度和限制性片段长度都有所不同。一些菌株与探针没有任何杂交信号。相反，来自广泛地理区域的其他菌株显然共享非常相似的亚基。通过对A43和一个突变的A43因子进行比较限制性酶切图谱分析，我们推断A因子中一个12 kb的缺失导致了突变A因子的组成型显性表型。转化实验的结果支持了A因子在调节A途径活性方面的激活剂模型。
