Long interspersed nuclear element

ORF2 protein (exhibiting reverse transcriptase and endonuclease activity) from human LINE-1.
Genetic structure of murine LINE1 and SINEs. Bottom: proposed structure of L1 RNA-protein (RNP) complexes. ORF1 proteins form trimers, exhibiting RNA binding and nucleic acid chaperone activity.

Long interspersed nuclear elements (LINEs)[1] (also known as long interspersed nucleotide elements[2] or long interspersed elements[3]) are a group of non-LTR (long terminal repeat) retrotransposons that are widespread in the genome of many eukaryotes.[4][5] LINEs contain an internal Pol II promoter to initiate transcription into mRNA, and encode one or two proteins, ORF1 and ORF2.[6] The functional domains present within ORF1 vary greatly among LINEs, but often exhibit RNA/DNA binding activity. ORF2 is essential to successful retrotransposition, and encodes a protein with both reverse transcriptase and endonuclease activity.[7]

LINEs are the most abundant transposable element within the human genome,[8] with approximately 20.7% of the sequences identified as being derived from LINEs. The only active lineage of LINE found within humans belongs to the LINE-1 class, and is referred to as L1Hs.[9] The human genome contains an estimated 100,000 truncated and 4,000 full-length LINE-1 elements.[10] Due to the accumulation of random mutations, the sequence of many LINEs has degenerated to the extent that they are no longer transcribed or translated. Comparisons of LINE DNA sequences can be used to date transposon insertions in the genome.

  1. ^ Ewing AD, Kazazian HH (June 2011). "Whole-genome resequencing allows detection of many rare LINE-1 insertion alleles in humans". Genome Research. 21 (6): 985–990. doi:10.1101/gr.114777.110. PMC 3106331. PMID 20980553.
  2. ^ Huang X, Su G, Wang Z, Shangguan S, Cui X, Zhu J, et al. (March 2014). "Hypomethylation of long interspersed nucleotide element-1 in peripheral mononuclear cells of juvenile systemic lupus erythematosus patients in China". International Journal of Rheumatic Diseases. 17 (3): 280–290. doi:10.1111/1756-185X.12239. PMID 24330152. S2CID 6530689.
  3. ^ Rodić N, Burns KH (March 2013). "Long interspersed element-1 (LINE-1): passenger or driver in human neoplasms?". PLOS Genetics. 9 (3): e1003402. doi:10.1371/journal.pgen.1003402. PMC 3610623. PMID 23555307.
  4. ^ Singer MF (March 1982). "SINEs and LINEs: highly repeated short and long interspersed sequences in mammalian genomes". Cell. 28 (3): 433–434. doi:10.1016/0092-8674(82)90194-5. PMID 6280868. S2CID 22129236.
  5. ^ Jurka J (June 1998). "Repeats in genomic DNA: mining and meaning". Current Opinion in Structural Biology. 8 (3): 333–337. doi:10.1016/S0959-440X(98)80067-5. PMID 9666329.
  6. ^ Feng Q, Moran JV, Kazazian HH, Boeke JD (November 1996). "Human L1 retrotransposon encodes a conserved endonuclease required for retrotransposition". Cell. 87 (5): 905–916. doi:10.1016/s0092-8674(00)81997-2. PMID 8945517. S2CID 17897241.
  7. ^ Eickbush TH, Jamburuthugoda VK (June 2008). "The diversity of retrotransposons and the properties of their reverse transcriptases". Virus Research. 134 (1–2): 221–234. doi:10.1016/j.virusres.2007.12.010. PMC 2695964. PMID 18261821.
  8. ^ Nurk S, Koren S, Rhie A, Rautiainen M, Bzikadze AV, Mikheenko A, et al. (April 2022). "The complete sequence of a human genome". Science. 376 (6588): 44–53. Bibcode:2022Sci...376...44N. doi:10.1126/science.abj6987. PMC 9186530. PMID 35357919.
  9. ^ McMillan JP, Singer MF (December 1993). "Translation of the human LINE-1 element, L1Hs". Proceedings of the National Academy of Sciences of the United States of America. 90 (24): 11533–11537. Bibcode:1993PNAS...9011533M. doi:10.1073/pnas.90.24.11533. PMC 48018. PMID 8265584.
  10. ^ Sheen FM, Sherry ST, Risch GM, Robichaux M, Nasidze I, Stoneking M, et al. (October 2000). "Reading between the LINEs: human genomic variation induced by LINE-1 retrotransposition". Genome Research. 10 (10): 1496–1508. doi:10.1101/gr.149400. PMC 310943. PMID 11042149.