Cianetti L, Testa U, Scotto L, La Valle R, Simeone A, Boccoli G, Giannella G, Peschle C, Boncinelli E
Department of Hematology-Oncology, Istituto Superiore di Sanità, Rome, Italy.
Immunogenetics. 1989;29(2):80-91. doi: 10.1007/BF00395855.
Sixteen HLA class I clones have been isolated from a SV40-transformed human fibroblast line (GM637) cDNA library. The clones, characterized by hybridization to ABC locus-specific probes and sequence analysis, correspond to transcripts from four different class I genes: A2, A10, Cw4, and Cw6 (or Cw7), as implied by cell typing. Only the A2 sequence was known. The nucleotide and deduced amino acid sequence of the new alleles are reported here, and their structural features are discussed. Two independent cDNAs of A2 specificity display an unusual polyadenylation site located 100 bp upstream from the canonical one. Moreover, two cDNAs pertaining to the same C allele display two alternative mechanisms of splicing, which cause either presence or absence in mature transcripts of the transmembrane exon 5 sequence. Transcripts missing this region are predicted to synthesize a nonmembrane-bound, secreted antigen. A soluble protein, specifically reacting with class I-specific HLA antibodies, is found in the supernatant of the GM637 cells. The significance of HLA class I transcripts generated by differential processing is discussed.
已从一个SV40转化的人成纤维细胞系（GM637）cDNA文库中分离出16个HLA I类克隆。这些克隆通过与ABC位点特异性探针杂交和序列分析进行表征，对应于四个不同I类基因的转录本：A2、A10、Cw4和Cw6（或Cw7），细胞分型结果暗示了这一点。只有A2序列是已知的。本文报道了新等位基因的核苷酸和推导的氨基酸序列，并讨论了它们的结构特征。两个具有A2特异性的独立cDNA显示出一个不寻常的多聚腺苷酸化位点，位于典型位点上游100 bp处。此外，属于同一C等位基因的两个cDNA显示出两种不同的剪接机制，这导致跨膜外显子5序列在成熟转录本中要么存在要么缺失。预计缺失该区域的转录本会合成一种非膜结合的分泌性抗原。在GM637细胞的上清液中发现了一种可溶蛋白，它能与I类特异性HLA抗体发生特异性反应。文中讨论了通过差异加工产生的HLA I类转录本的意义。
