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.
LINE1 (an abbreviation of Long interspersed nuclear element-1, also known as L1 and LINE-1) is a family of related class I transposable elements in the DNA of many groups of eukaryotes, including animals and plants, classified with the long interspersed nuclear elements (LINEs).[1] L1 transposons are most ubiquitous in mammals, where they make up a significant fraction of the total genome length,[1][2] for example they comprise approximately 17% of the human genome.[3] These active L1s can interrupt the genome through insertions, deletions, rearrangements, and copy number variations.[4] L1 activity has contributed to the instability and evolution of genomes and is tightly regulated in the germline by DNA methylation, histone modifications, and piRNA.[5] L1s can further impact genome variation through mispairing and unequal crossing over during meiosis due to its repetitive DNA sequences.[4]
L1 gene products are also required by many non-autonomous Alu and SVA SINE retrotransposons. Mutations induced by L1 and its non-autonomous counterparts have been found to cause a variety of heritable and somatic diseases.[6][7]