Miyata T, Yasunaga T, Yamawaki-Kataoka Y, Obata M, Honjo T
Proc Natl Acad Sci U S A. 1980 Apr;77(4):2143-7. doi: 10.1073/pnas.77.4.2143.
The nucleotide sequences of the constant portions of mouse immunoglobulin gamma 1 and gamma 2b genes were compared. A remarkable homology was found in a long (about 500 nucleotides) continuous segment including the entire CH1 coding region and about the first half of the first intervening sequence. Furthermore, comparison of amino acid sequences of four gamma-class chains revealed that the CH1 domain shows limited divergence among gamma 1, gamma 2a, and gamma 2b. Interestingly, the homology region extends to the CH2 domain in gamma 2a and gamma 2b. These findings suggest that, during their evolution, a double unequal crossing-over event has taken place at different intervening sequences, resulting in the transfer of the DNA segment coding for the CH1 domain or CH1-CH2 domains. A possible evolutionary implication for such an "intervening sequence-mediated domain transfer" event is discussed.
对小鼠免疫球蛋白γ1和γ2b基因恒定区的核苷酸序列进行了比较。在一个长约500个核苷酸的连续片段中发现了显著的同源性，该片段包括整个CH1编码区和约第一个内含子序列的前半部分。此外，对四条γ类链氨基酸序列的比较表明，CH1结构域在γ1、γ2a和γ2b之间显示出有限的差异。有趣的是，同源区域在γ2a和γ2b中延伸至CH2结构域。这些发现表明，在它们的进化过程中，在不同的内含子序列处发生了一次双重不等交换事件，导致编码CH1结构域或CH1-CH2结构域的DNA片段发生转移。讨论了这种“内含子序列介导的结构域转移”事件可能的进化意义。
