Iα exon-replacement mice synthesize a spliced HPRT-Cα transcript which may explain their ability to switch to IgA.: Inhibition of switching to IgG in these mice
Iα exon-replacement mice synthesize a spliced HPRT-Cα transcript which may explain their ability to switch to IgA.: Inhibition of switching to IgG in these mice
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DOI：
10.1093/intimm/11.1.37
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发表时间：
1999-01-01
影响因子：
4.4
通讯作者：
Stavnezer, J
中科院分区：
文献类型：
--
作者：
Qiu, G;Harriman, GR;Stavnezer, J
抗体类别转换受未重排CH基因的转录调节，以产生指导同种型选择并为转换所需的生殖系（GL）转录物。但其作用不明。GL转录起始于位于每个开关区上游的I外显子。尽管通过基因靶向缺失I外显子阻止了向该C-H基因的转换重组，但I-α外显子可以被完全不同的DNA片段取代，该DNA片段是由磷酸甘油酸激酶（PGK）启动子驱动并编码次黄嘌呤磷酸核糖基转移酶（HPRT）的小基因，以有义方向定向，而不会减少抗体类别向伊加的转换。为了理解为什么I-α外显子的HPRT取代不会破坏开关重组，我们分析了这些小鼠中靶向等位基因的转录物的结构。我们确定了一个剪接的转录本，其中HPRT外显子剪接到C-α基因片段，导致类似于正常GL转录本的结构。这种转录本的丰度与正常α GL RNA的丰度相似。我们还证明，与野生型小鼠相比，从这些小鼠的细胞中切换到四个IgG亚类的情况减少。我们讨论的可能性，强PGK启动子插入在IG α基因座可能会干扰γ GL转录物的启动子与3' IgH增强子的相互作用。
Antibody class switching is regulated by transcription of unrearranged CH genes to produce germline (GL) transcripts which direct the choice of isotype and are required for switching. However, their role is unknown. GL transcripts are initiated at the I exons located upstream of each switch region. Although deletion of the I exon by gene targeting prevents switch recombination to that C-H gene, the I-alpha exon can be replaced by an entirely different DNA segment, a minigene driven by the phosphoglycerate kinase (PGK) promoter and encoding hypoxanthine phosphoribosyl transferase (HPRT), oriented in the sense direction, without reducing antibody class switching to IgA. To understand why HPRT substitution of the I-alpha exon does not disrupt switch recombination, we have analyzed the structure of the transcript from the targeted allele in these mice. We identify a spliced transcript in which the HPRT exons are spliced to the C-alpha gene segments, resulting in a structure similar to normal GL transcripts. The abundance of this transcript is similar to that of the normal alpha GL RNA. We also demonstrate that switching to the four IgG subclasses in a cells from these mice is reduced in comparison to wild-type mice. We discuss the possibility that the strong PGK promoter inserted at the Ig alpha locus may interfere with interaction of the promoters for gamma GL transcripts with the 3' IgH enhancer.