Ohtake Y, Wickner R B
Section on Genetics of Simple Eukaryotes, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Genetics. 1995 May;140(1):129-37. doi: 10.1093/genetics/140.1.129.
The mak7-1 mutant loses the killer toxin-encoding M1 dsRNA. MAK7 is RPL4A, one of two genes encoding ribosomal protein L4. KRB1 is a dominant suppressor of mak7-1 that is tightly centromerelinked, but not linked to centromere markers of chromosomes I-XVI. Our orthogonal field agarose gel electrophoresis analysis of chromosomal DNA from strains with KRB1 shows a novel band of approximately 250 kb. This band hybridizes with an RPL4B-specific probe, but not an RPL4A (MAK7)-specific probe. The RPL4B-specific probe also hybridizes to chromosome XII where the original RPL4B is located. KRB1 is meiotically linked to this extra chromosome. Disruption of either the RPL4B gene on chromosome XII or that on the extra chromosome results in loss of the killer phenotype and a decreased concentration of free 60S subunits. Thus, the RPL4B on the extra chromosome is KRB1 and is active. The extra chromosome contains chromosome XII sequence between Lambda 5345 clone (ATCC70558) and Lambda 6639 clone (ATCC71085) of Olson's Lambda library, indicating that KRB1 represents a chromosomal rearrangement involving chromosome XII and explaining the earlier genetic data.
mak7-1突变体失去了编码杀伤毒素的M1双链RNA。MAK7是RPL4A，即编码核糖体蛋白L4的两个基因之一。KRB1是mak7-1的显性抑制因子，与着丝粒紧密连锁，但与I-XVI号染色体的着丝粒标记不连锁。我们对带有KRB1的菌株的染色体DNA进行正交场琼脂糖凝胶电泳分析，显示出一条约250 kb的新条带。这条带与RPL4B特异性探针杂交，但不与RPL4A（MAK7）特异性探针杂交。RPL4B特异性探针也与原始RPL4B所在的XII号染色体杂交。KRB1在减数分裂时与这条额外的染色体连锁。破坏XII号染色体上或额外染色体上的RPL4B基因都会导致杀伤表型丧失和游离60S亚基浓度降低。因此，额外染色体上的RPL4B就是KRB1且具有活性。这条额外的染色体包含了奥尔森λ文库中λ5345克隆（ATCC70558）和λ6639克隆（ATCC71085）之间的XII号染色体序列，这表明KRB1代表了涉及XII号染色体的染色体重排，并解释了早期的遗传数据。
