Linking maternal and somatic 5S rRNA types with different sequence-specific non-LTR retrotransposons
Linking maternal and somatic 5S rRNA types with different sequence-specific non-LTR retrotransposons
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DOI：
10.1261/rna.059642.116
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发表时间：
2017-04-01
期刊：
影响因子：
4.5
通讯作者：
Breit, Timo M.
中科院分区：
文献类型：
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作者：
Locati, Mauro D.;Pagano, Johanna F. B.;Breit, Timo M.
5S rRNA是核糖体核心组分，由以基因组重复序列组织的许多基因拷贝转录而成。一些真核生物有两种5S rRNA类型，它们主要在卵子发生或成体组织中表达。我们对斑马鱼卵、胚胎和成体组织进行的下一代测序研究确定了母源型5S rRNA，其仅在卵子发生过程中积累，在整个胚胎发生过程中被体细胞型所取代，因此在成体体细胞组织中几乎不存在。母型5S rDNA在4号染色体上含有数千个基因拷贝，串联重复，基因间区域较小，而体细胞型仅在18号染色体上存在12个基因拷贝，基因间区域较大。两种5S rRNA类型之间的9个核苷酸的变异可能影响TFIII结合和核糖蛋白L5结合，可能导致母体型rRNA的储存。值得注意的是，这些序列差异正好位于5S rRNA特异性Mutsu逆转录转座子家族基因组整合的序列特异性靶位点。因此，我们可以定义母型和体细胞型MutsuDr亚家族。此外，我们确定了四个额外的母亲型和两个新的体细胞型MutsuDr亚家族，每个都有自己的目标序列。这种靶位点特异性，经常是完整的母体型反转录转座子元件，加上特定的存在Mutsu反转录转座子RNA和皮尔纳在鸡蛋和成人组织，表明反转录转座子参与实现差异拷贝数的两种类型的5S rDNA基因座。
5S rRNA is a ribosomal core component, transcribed from many gene copies organized in genomic repeats. Some eukaryotic species have two 5S rRNA types defined by their predominant expression in oogenesis or adult tissue. Our next-generation sequencing study on zebrafish egg, embryo, and adult tissue identified maternal-type 5S rRNA that is exclusively accumulated during oogenesis, replaced throughout the embryogenesis by a somatic-type, and thus virtually absent in adult somatic tissue. The maternal-type 5S rDNA contains several thousands of gene copies on chromosome 4 in tandem repeats with small intergenic regions, whereas the somatic-type is present in only 12 gene copies on chromosome 18 with large intergenic regions. The nine-nucleotide variation between the two 5S rRNA types likely affects TFIII binding and riboprotein L5 binding, probably leading to storage of maternal-type rRNA. Remarkably, these sequence differences are located exactly at the sequence-specific target site for genome integration by the 5S rRNA-specific Mutsu retrotransposon family. Thus, we could define maternal-and somatic-type MutsuDr subfamilies. Furthermore, we identified four additional maternal-type and two new somatic-type MutsuDr subfamilies, each with their own target sequence. This target-site specificity, frequently intact maternal-type retrotransposon elements, plus specific presence of Mutsu retrotransposon RNA and piRNA in egg and adult tissue, suggest an involvement of retrotransposons in achieving the differential copy number of the two types of 5S rDNA loci.