Meyer E, Caron F, Baroin A
Mol Cell Biol. 1985 Sep;5(9):2414-22. doi: 10.1128/mcb.5.9.2414-2422.1985.
The gene encoding the G surface antigen of Paramecium primaurelia was cloned from a macronuclear DNA library by a screening procedure involving differential hybridization with cDNA probes synthesized from polyadenylated RNAs of cells expressing one of two alternate antigens. S1 mapping experiments and sequencing of the cloned DNA and the mRNA showed that the cloned gene corresponded to the high-molecular-weight mRNA that had been indirectly identified as that of the G surface antigen. Because the genetic code of Paramecium spp. is different from the "universal" code, this mRNA cannot be correctly translated in vitro; direct proof that it encoded the antigenic determinants of this protein was therefore obtained through expression of fragments of the coding sequence in Escherichia coli by using the expression vector lambda gt11. Studies on the structure of this gene revealed that the central part of the coding sequence contained at least five tandem repeats of 222 base pairs, encoding immunogenic domains of the protein. We also showed that, like other surface antigen genes of trypanosomes and paramecia, this gene lay next to a chromosome end and that no rearrangement of its immediate genomic environment was associated with its expression.
通过一种筛选程序，从大核DNA文库中克隆了编码草履虫（Paramecium primaurelia）G表面抗原的基因。该筛选程序涉及用从表达两种交替抗原之一的细胞的多聚腺苷酸化RNA合成的cDNA探针进行差异杂交。S1图谱实验以及对克隆的DNA和mRNA的测序表明，克隆的基因对应于已被间接鉴定为G表面抗原的高分子量mRNA。由于草履虫属的遗传密码与“通用”密码不同，这种mRNA在体外不能被正确翻译；因此，通过使用表达载体λgt11在大肠杆菌中表达编码序列的片段，获得了它编码该蛋白质抗原决定簇的直接证据。对该基因结构的研究表明，编码序列的中部包含至少五个222个碱基对的串联重复序列，编码该蛋白质的免疫原性结构域。我们还表明，与锥虫和草履虫的其他表面抗原基因一样，该基因位于染色体末端附近，并且其直接基因组环境的重排与其表达无关
