Jäck H M, McDowell M, Steinberg C M, Wabl M
Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143.
Proc Natl Acad Sci U S A. 1988 Mar;85(5):1581-5. doi: 10.1073/pnas.85.5.1581.
In the mouse pre-B-cell line 18-81, cells can switch production in vitro from immunoglobulin mu chain to gamma 2b chain. The gene encoding the gamma 2b chain is created by a rearrangement of the mu gene. This rearrangement always takes place within a homolog. In cells with a gamma 2b gene, most of the time the gene segment encoding the constant region of the mu chain is deleted, but often the rearrangement leads to cells that produce no immunoglobulin, and all DNA sequences are retained. The latter result is due to an inversion. Inversions exclude the unequal sister chromatid exchange model of the heavy-chain class switch. Looping out is an intermediate step in the process of generating an inversion. Our findings demonstrate that the switch rearrangement occurs by looping out and deletion.
在小鼠前B细胞系18 - 81中，细胞能够在体外将免疫球蛋白μ链的产生转换为γ2b链。编码γ2b链的基因是由μ基因重排产生的。这种重排总是在同源物内发生。在具有γ2b基因的细胞中，大多数时候编码μ链恒定区的基因片段会被删除，但重排常常导致细胞不产生免疫球蛋白，且所有DNA序列都被保留。后一种结果是由于倒位。倒位排除了重链类别转换的不等姐妹染色单体交换模型。环出是产生倒位过程中的一个中间步骤。我们的研究结果表明，类别转换重排是通过环出和删除发生的。
