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首页> 外文期刊>Molecular and Cellular Biology >Coordination of immunoglobulin DJH transcription and D-to-JH rearrangement by promoter-enhancer approximation.
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Coordination of immunoglobulin DJH transcription and D-to-JH rearrangement by promoter-enhancer approximation.

机译：免疫球蛋白DJH转录和D-JH重排的启动子-增强子协调作用。

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The genes that encode the variable regions of immunoglobulin (Ig) heavy chains are encoded by three DNA segments: VH, D, and JH. During B-cell development these segments are brought together by a pair of site-specific DNA rearrangements. The first of these joins a D segment to a JH segment; the second brings a VH segment in apposition to a DJH unit. B-cell precursors that have undergone D-to-JH joining express transcripts that initiate at the 5' flanks of rearranged D segments (DJH transcription). In this study we have examined the coordination of D-to-JH rearrangement and DJH transcription. The B-lymphoid progenitor cell line HAFTL-1 cell clone, joining of distal D segments (DSP2 and DFL16) to JH is accompanied by an increase in the steady-state level of transcripts initiating 5' of the D coding region. Steady-state transcription of a DSP2 gene segment was undetectable prior to rearrangement and was observed to increase at least 20-fold upon joining to JH. In contrast, transcription from the 5' flank of DQ52, which lies within 700 bp of the JH cluster, was detected prior to rearrangement and did not increase significantly after rearrangement. The 5' flank of a DSP2 segment was found to support expression of a heterologous gene upon transfection into B progenitor cell lines. Expression from this DSP2 promoter was at least 30-fold higher in the presence of the Ig heavy-chain enhancer, in either orientation, than in its absence. A DNA fragment spanning the interval from -165 to +19 bp relative to the major DSP2 transcriptional start site retained enhancer-dependent promoter activity. These observations imply that activation of DSP12JH and DFL16JH transcription is coordinated with D-to-JH rearrangement by approximation of enhancer-dependent D promoter elements to the Ig heavy-chain enhancer. This interpretation is consistent with our observation that the DQ52 segment, which is closely linked to the JH cluster, is transcribed both before and after rearrangement.
机译：编码免疫球蛋白（Ig）重链可变区的基因由三个DNA片段编码：VH，D和JH。在B细胞发育过程中，这些片段通过一对位点特异性DNA重排而聚集在一起。其中第一个将D段连接到JH段;第二个将VH段与DJH单元并置。经历了D到JH连接的B细胞前体表达的转录本起始于重排D片段的5'侧翼（DJH转录）。在这项研究中，我们检查了D至JH重排和DJH转录的协调。 B淋巴祖细胞系HAFTL-1细胞克隆，远端D区段（DSP2和DFL16）与JH的连接伴随着起始D编码区5'的转录本稳态水平的提高。在重排之前无法检测到DSP2基因片段的稳态转录，并且观察到加入JH后其至少增加了20倍。相反，在重排之前检测到来自DQ52 5'侧翼的转录，该序列位于JH簇的700 bp之内，并且在重排之后没有明显增加。发现转染到B祖细胞系中后，DSP2区段的5'侧翼支持异源基因的表达。在存在Ig重链增强子的情况下，在任一方向上，该DSP2启动子的表达都比不存在时高至少30倍。相对于主要DSP2转录起始位点，DNA片段的跨度介于-165到+19 bp之间，保留了增强子依赖性启动子活性。这些观察结果暗示DSP12JH和DFL16JH转录的激活通过将依赖于增强子的D启动子元件近似于Ig重链增强子而与D至JH重排协调。这种解释与我们的观察一致，即与JH簇紧密相关的DQ52节在重排前后均被转录。

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