Denis-Duphil M, Kaplan J G
Mol Gen Genet. 1976 Jun 15;145(3):259-71. doi: 10.1007/BF00325822.
The URA2 locus codes for a multifunctional enzyme complex carrying aspartate transcarbamylase (ATCase) and carbamyly phosphate synthetase (CPSase) activities. Three different types of ura2 mutants were tested in meiotic and mitotic recombination experiments: ura2A mutants devoid of ATCase activity, ura2C mutants devoid of CPSase activity and ura2B mutants devoid of both activities. All the ura2A mutations were found to be clustered at one end of the URA2 locus, called zone A, while the ura2C mutations were localized in a region at the other end, called zone C. All but two ura2B mutations (most of them suppressible) were distributed throughout zone C; the two ura2B exceptions which are small deletions, mapped in zone A. On the meiotic as well as on the mitotic map an intermediary or dead-space zone is located between zones A and C. No mutation has yet been found to map in this zone. The relative lengths of the three zones A, intermediary and C are 1 :2-3 :3-4, respectively. These data are consistent with the hypothesis that the URA2 locus consisting of at least two cistrons: C (CPSase) and A (ATCase), is transcribed into a single polycistronic message in the direction C to A. However, alternative hypotheses in reference to Peterson and MacLaughlin's observations (1973) are discussed.
URA2基因座编码一种多功能酶复合物，具有天冬氨酸转氨甲酰酶（ATCase）和氨甲酰磷酸合成酶（CPSase）活性。在减数分裂和有丝分裂重组实验中测试了三种不同类型的ura2突变体：缺乏ATCase活性的ura2A突变体、缺乏CPSase活性的ura2C突变体和缺乏两种活性的ura2B突变体。发现所有ura2A突变都聚集在URA2基因座的一端，称为A区，而ura2C突变则定位在另一端的一个区域，称为C区。除两个ura2B突变（大多数可被抑制）外，所有突变都分布在整个C区；这两个ura2B例外是小缺失，定位在A区。在减数分裂和有丝分裂图谱上，A区和C区之间有一个中间或空白区域。尚未发现有突变定位在该区域。A区、中间区和C区的相对长度分别为1:2 - 3:3 - 4。这些数据与以下假设一致，即由至少两个顺反子组成的URA2基因座：C（CPSase）和A（ATCase），以C到A的方向转录成单个多顺反子信息。然而，也讨论了与彼得森和麦克劳克林的观察结果（1973年）相关的其他假设。
