期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：17
页码：7699-7703
DOI：10.1073/pnas.88.17.7699
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Unlike mammals, chickens generate an immunoglobulin (Ig) repertoire by a developmentally regulated process of intrachromosomal gene conversion, which results in nucleotide substitutions throughout the variable regions of the Ig heavy- and light-chain genes. In contrast to chicken Ig genes, we show in this report that diversity of the rearranged chicken T-cell receptor (TCR) beta-chain gene is generated by junctional heterogeneity, as observed in rearranged mammalian TCR genes. This junctional diversity increases during chicken development as a result of an increasing base-pair addition at the V beta-D beta and D beta-J beta joints (where V, D, and J are the variable, diversity, and joining gene segments). Despite the junctional hypervariability, however, almost all functional V beta-D beta-J beta junctions appear to encode a glycine-containing beta-turn. Such a turn may serve to position the amino acid side chains of a hypervariable TCR beta-chain loop with respect to the antigen-binding groove of the major histocompatibility complex molecule. Consistent with this hypothesis, the germ-line D beta nucleotide sequences of chickens, mice, rabbits, and humans have been highly conserved and encode a glycine in all three reading frames.
