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首页> 外文期刊>American Zoologist >Toward an understanding of satellite DNA function in Crustacea
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Toward an understanding of satellite DNA function in Crustacea

机译：了解甲壳纲中卫星DNA的功能

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A G+C-rich Satellite DNA (stDNA) in Gecarcinus lateralis with a repeat unit of 2.1 kbp makes up approximately 3% (16,000 copiesucleus) of the land crab genome. We used sequences from conserved domains of the repeat unit to construct probes for exploring the possibility of the repeat units being transcribed into RNA, their distribution in genomic DNA, and their methylation status. A transcription product hybridizing with TRU-EXON, a region of the satellite bordered by possible exon splice junctions, was found only in land crabs, whereas transcription products that hybridized to 3'END, a 368 bp fragment at the 3'-end of the satellite, were also found in several other crustaceans. Transcription products that hybridized to AMPL-3, a probe from an amplified segment of the satellite, were not found in land crabs but were found in lobsters. In land crabs, several poly(A)+RNA transcripts that hybridized to 3'END were specific for DNA strand, tissue, and intermolt stage. The diversity of transcripts suggests that transcription of the satellite is related to the organization of the repeated DNA in the crab genome, and that some satellite domains may be transcribed because of their position relative to functional genes. This observation is supported by the additional observation that the satellite is differentially methylated. Repeats organized in tandem in the satellite are methylated, whereas those interspersed in main component DNA (mcDNA) are not. Because DNA methylation is a means of silencing transcription, our results suggest that satellite sequences that are transcribed are those interpersed in mcDNA. DNA methylation patterns are also tissue-specific; of the seven tissues examined (gill, claw muscle, body muscle, limb buds, midgut gland, testis, and ovary), gill stDNA is the least methylated. The observed differences in methylation levels are not attributable to stage in the intermolt cycle or to sex. This is the first report indicating the presence of 5-methylcytosine (m(5)C) in a crustacean.
机译：侧盖Gecarcinus中具有一个富含G + C的卫星DNA（stDNA），其重复单元为2.1 kbp，约占陆地蟹基因组的3％（16,000拷贝/核）。我们使用了来自重复单元保守域的序列来构建探针，以探索重复单元转录成RNA的可能性，它们在基因组DNA中的分布以及它们的甲基化状态。仅在陆地蟹中发现了与TRU-EXON杂交的转录产物，TRU-EXON是与可能的外显子剪接点接壤的卫星区域，而与3'END杂交的转录产物与3'END杂交，在3'END的3'末端卫星，也发现在其他几个甲壳动物中。在陆地蟹中未发现与AMPL-3（来自卫星扩增片段的探针）杂交的转录产物，但在龙虾中却发现了转录产物。在陆地蟹中，与3'END杂交的几种poly（A）+ RNA转录本对DNA链，组织和互熔期具有特异性。转录本的多样性表明，卫星的转录与蟹基因组中重复的DNA的组织有关，并且某些卫星域可能因其相对于功能基因的位置而被转录。该观察结果得到卫星被甲基化差异化的其他观察结果的支持。在卫星中串联排列的重复序列被甲基化，而散布在主要成分DNA（mcDNA）中的序列则不被甲基化。因为DNA甲基化是沉默转录的一种手段，所以我们的结果表明，转录的卫星序列是散布在mcDNA中的序列。 DNA甲基化模式也是组织特异性的。在所检查的七个组织（g，爪肌，身体肌肉，肢芽，中肠腺，睾丸和卵巢）中，g stDNA的甲基化最少。观察到的甲基化水平差异不归因于互熔周期的阶段或性别。这是第一个报告，表明甲壳动物中存在5-甲基胞嘧啶（m（5）C）。

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