短散在核元件
短散在核元件（Short interspersed nuclear elements，简称SINE）是真核生物基因组中长100至700bp的转位子序列[1]，属于反转录转座子，哺乳类基因组约有13%为SINE[2]。SINE与LINE等转位子皆是“寄生”于生物基因组中的DNA元件，某些情况下可能对生物体有害，但有时细胞也将其用来调控自己的基因表现[3]。
SINE一般不具有长末端重复序列（LTR）[4]，其序列从5端至3端可大致分为头端、中端与尾端三部分，其中头端大多来自tRNA等由RNA聚合酶III转录的RNA[5]，例如Alu元件的5端序列即来自7SL RNA[6]；中端序列常与长散在核元件（LINE）相似，因此可利用后者编码的内切酶；尾端则是由一些重复序列组成[7]。
SINE头端的序列与tRNA等小RNA相似，可被RNA聚合酶III转录[8]，且其启动子和tRNA一样是转录序列的一部分（称为“内部启动子”），而非位于其上游[9]。SINE转录出的mRNA不编码任何蛋白质，相较之下LINE可编码具内切酶和反转录酶活性的蛋白，SINE因具有和LINE同源的序列[10]，其RNA跟LINE的RNA均可利用这些蛋白，反转录成DNA后再随机插入基因组中[4][11]。SINE因需仰赖基因组中的其他序列编码的酵素才能增殖，属于非自主的逆转录转座子（non-autonomous retrotransposon），而LINE则是自主的逆转录转座子（autonomous retrotransposon）[12]。LINE的转录在生殖系细胞和早期胚胎中较为活跃，因此SINE也大多在这些阶段转录增殖，胚胎发育后期以后，体细胞中SINE的转录一般会被抑制，不过某些状况下可能使其恢复表现[13]。
Alu元件是灵长类演化过程中相当重要的SINE，约长300bp，人类基因组中有超过百万个Alu元件，占基因组大小超过10%[14]，许多其他动物基因组中也有大量的SINE[15]。SINE插入重要的基因序列可影响基因表现而造成人类的遗传疾病[13][16] ，例如有些乳癌、大肠癌、白血病、血友病、囊肿性纤维化、神经纤维瘤病与Dent病为Alu元件插入造成[4]。
参考文献
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- ^ Vassetzky NS, Kramerov DA. SINEBase: a database and tool for SINE analysis. Nucleic Acids Research. January 2013, 41 (Database issue): D83–9. PMC 3531059
. PMID 23203982. doi:10.1093/nar/gks1263.
- ^ Ishak, Charles A.; De Carvalho, Daniel D. Reactivation of Endogenous Retroelements in Cancer Development and Therapy. Annual Review of Cancer Biology. 2020, 4: 159–176. doi:10.1146/annurev-cancerbio-030419-033525.
- ^ Kramerov DA, Vassetzky NS. SINEs.. Wiley Interdiscip Rev RNA. 2011, 2 (6): 772–86. PMID 21976282. doi:10.1002/wrna.91.
- ^ 4.0 4.1 4.2 Hancks DC, Kazazian HH. Active human retrotransposons: variation and disease. Current Opinion in Genetics & Development. 2012, 22 (3): 191–203. PMC 3376660 . PMID 22406018. doi:10.1016/j.gde.2012.02.006.
- ^ Wicker T, Sabot F, Hua-Van A, Bennetzen JL, Capy P, Chalhoub B, et al. A unified classification system for eukaryotic transposable elements. Nature Reviews. Genetics. December 2007, 8 (12): 973–82. PMID 17984973. doi:10.1038/nrg2165.
- ^ Kriegs JO, Churakov G, Jurka J, Brosius J, Schmitz J. Evolutionary history of 7SL RNA-derived SINEs in Supraprimates. Trends in Genetics. April 2007, 23 (4): 158–61. PMID 17307271. doi:10.1016/j.tig.2007.02.002.
- ^ Okada N, Hamada M, Ogiwara I, Ohshima K. SINEs and LINEs share common 3' sequences: a review. Gene. December 1997, 205 (1–2): 229–43. PMID 9461397. doi:10.1016/s0378-1119(97)00409-5.
- ^ Deininger PL, Batzer MA. Mammalian retroelements. Genome Research. October 2002, 12 (10): 1455–65. PMID 12368238. doi:10.1101/gr.282402.
- ^ White RJ. Transcription by RNA polymerase III: more complex than we thought. Nature Reviews. Genetics. May 2011, 12 (7): 459–63. PMID 21540878. doi:10.1038/nrg3001.
- ^ Singer MF. SINEs and LINEs: highly repeated short and long interspersed sequences in mammalian genomes. Cell. March 1982, 28 (3): 433–4. PMID 6280868. doi:10.1016/0092-8674(82)90194-5.
- ^ Mätlik K, Redik K, Speek M. L1 antisense promoter drives tissue-specific transcription of human genes. Journal of Biomedicine & Biotechnology. 2006, 2006 (1): 71753. PMC 1559930 . PMID 16877819. doi:10.1155/JBB/2006/71753.
- ^ Gogvadze E, Buzdin A. Retroelements and their impact on genome evolution and functioning. Cellular and Molecular Life Sciences. December 2009, 66 (23): 3727–42. PMID 19649766. doi:10.1007/s00018-009-0107-2.
- ^ 13.0 13.1 Beauregard A, Curcio MJ, Belfort M. The take and give between retrotransposable elements and their hosts. Annual Review of Genetics. 2008, 42: 587–617. PMC 2665727 . PMID 18680436. doi:10.1146/annurev.genet.42.110807.091549.
- ^ Cordaux R, Batzer MA. The impact of retrotransposons on human genome evolution. Nature Reviews. Genetics. October 2009, 10 (10): 691–703. PMC 2884099 . PMID 19763152. doi:10.1038/nrg2640.
- ^ Chalopin D, Naville M, Plard F, Galiana D, Volff JN. Comparative analysis of transposable elements highlights mobilome diversity and evolution in vertebrates. Genome Biology and Evolution. January 2015, 7 (2): 567–80. PMC 4350176 . PMID 25577199. doi:10.1093/gbe/evv005.
- ^ Wang W, Kirkness EF. Short interspersed elements (SINEs) are a major source of canine genomic diversity. Genome Research. December 2005, 15 (12): 1798–808. PMC 1356118 . PMID 16339378. doi:10.1101/gr.3765505.
