Multiple types of chimeric germ-line Ig heavy chain transcripts in human B cells: evidence for trans-splicing of human Ig RNA.
Multiple types of chimeric germ-line Ig heavy chain transcripts in human B cells: evidence for trans-splicing of human Ig RNA.
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DOI：
10.4049/jimmunol.157.8.3450
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发表时间：
1996-10
影响因子：
4.4
通讯作者：
S. Fujieda;Yin Qiang Lin;A. Saxon;Ke Zhang
中科院分区：
文献类型：
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作者：
S. Fujieda;Yin Qiang Lin;A. Saxon;Ke Zhang
来自IG重链位点的生殖系转录物先于同种型转换的发生，并且被认为在IG类转换中发挥重要但仍有争议的作用。在这项研究中，我们采用了逆转录酶-PCR方法来检测人类嵌合IG生殖系mRNA转录本。在仅用IL-4刺激的人B细胞中容易检测到多种类型的嵌合IG生殖系转录物（Imu-Cmu、Iepsilon-Cmu、Imu-Cgamma4、Igamma-Cmu、Iepsilon-Cgamma和Igamma4-Calpha1转录物）。序列分析显示，所有这些嵌合IG生殖系转录本代表来自一个IG基因座的I外显子通过使用剪接供体和受体位点的共有序列剪接到来自另一个基因座的CH外显子，表明它们通过剪接机制产生。在仅用IL-4刺激人静息B细胞的情况下，嵌合IG种系转录物可能来源于反式剪接机制，因为广泛的检索未发现发生IG类别转换重组的证据，这可能通过反式剪接以外的机制产生嵌合IG mRNA。类似地，EBV转化的γ 2重排的B细胞系GM 1500产生IgG 2并含有γ 2生产性和嵌合生殖系转录物，也表达嵌合生殖系RNA（ε-C γ 2）和ε-生产性转录物（VDJ-C γ 2）。该细胞系没有进一步的连续Sgamma2-Separate重排，提供了证据表明，生产VDJ-CXCRmRNA来自转录活性的未重排的CXCRmRNA基因位点通过反式剪接。总之，这些结果提供了可能的证据，生殖系IG RNA转录本的反式剪接发生在人类B细胞。
Germ-line transcripts from Ig heavy chain loci precede the occurrence of isotype switching and are thought to play an important though still controversial role in Ig class switching. In this study, we employed a reverse transcriptase-PCR approach to detect human chimeric Ig germ-line mRNA transcripts. Multiple types of chimeric Ig germ-line transcripts (Imu-Cepsilon, Iepsilon-Cmu, Imu-Cgamma4, Igamma-Cmu, Igamma-Cepsilon, Iepsilon-Cgamma, and Igamma4-Calpha1 transcripts) were readily detected in human B cells stimulated with IL-4 alone. Sequence analysis revealed that all of these chimeric Ig germ-line transcripts represented the I exons from one Ig locus spliced to the CH exons from another locus by using consensus sequences for splicing donor and acceptor sites, indicating that they were generated through splicing machinery. In the case of stimulation of human resting B cells with IL-4 alone, the chimeric Ig germ-line transcripts are likely derived from a trans-splicing mechanism, as the extensive searching did not find evidence that Ig class-switch recombination had occurred, which alternatively could give rise to chimeric Ig mRNA by mechanisms other than trans-splicing. Similarly, an EBV-transformed gamma2 rearranged B cell line, GM1500, which produces IgG2 and contains both gamma2 productive and epsilon germ-line transcripts, also expressed chimeric germ-line RNA (Iepsilon-Cgamma2) and epsilon-productive transcripts (VDJ-Cepsilon). This line had no further sequential Sgamma2-Sepsilon rearrangements, providing evidence that the productive VDJ-Cepsilon mRNA was derived from a transcriptionally active unrearranged epsilon gene locus by trans-splicing. Taken together, these results provide possible evidence that trans-splicing of germ-line Ig RNA transcripts occurs in human B cells.