Chomez P, De Plaen E, Van Pel A, De Smet C, Szikora J P, Lurquin C, Lebacq-Verheyden A M, Boon T
Ludwig Institute for Cancer Research, Brussels Branch, Belgium.
Immunogenetics. 1992;35(4):241-52. doi: 10.1007/BF00166829.
Mutagen treatment of mouse P815 tumor cells produces immunogenic mutants that express new transplantation antigens (tum- antigens) recognized by cytolytic T cells. The gene encoding tum- antigen P91A comprises 12 exons and a mutation located in exon 4 is responsible for the production of a new antigenic peptide. Transfection experiments showed that the expression of the antigen could be transferred not only by the entire gene but also by gene segments comprising only the mutated exon and parts of the surrounding introns. This was observed with subgenic regions that were not cloned in expression vectors. Antigen expression did not require the integration of the transfected gene segment into a resident P91A gene by homologous recombination. It also occurred when the subgenic segment was transfected without the usual selective gene, which comprises an eucaryotic promoter, and also without plasmid sequences, which are known to contain weak promoters. When a stop codon was introduced at the beginning of exon 4, the expression of the antigen was maintained and evidence was obtained that an ATG codon located in this region served as initiation site for the translation of the antigenic peptide. But we have not obtained evidence indicating that antigenic peptides are direct translation products rather than degradation products of entire proteins.
用诱变剂处理小鼠P815肿瘤细胞可产生免疫原性突变体，这些突变体表达被细胞毒性T细胞识别的新移植抗原（肿瘤抗原）。编码肿瘤抗原P91A的基因包含12个外显子，位于外显子4中的一个突变负责产生新的抗原肽。转染实验表明，不仅整个基因可转移抗原的表达，仅包含突变外显子和部分周围内含子的基因片段也可转移抗原的表达。在未克隆到表达载体中的亚基因区域也观察到了这种情况。抗原表达不需要通过同源重组将转染的基因片段整合到常驻P91A基因中。当亚基因片段在没有通常包含真核启动子的选择基因以及已知含有弱启动子的质粒序列的情况下进行转染时，也会发生抗原表达。当在外显子4的起始处引入一个终止密码子时，抗原的表达得以维持，并且有证据表明位于该区域的一个ATG密码子作为抗原肽翻译的起始位点。但我们尚未获得证据表明抗原肽是直接翻译产物而非完整蛋白质的降解产物。
