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LINE1 (also L1 and LINE-1) are transposable elements in the DNA of some organisms and belong to the group of Long interspersed nuclear elements (LINEs). L1 comprise approximately 17% of the human genome.
Contents
The majority of L1 in the human genome are inactive; however, some retained the ability to retrotranspose. Human L1 has been reported to have transferred to the genome of the gonorrhea bacteria.
Structure
A typical L1 element is approximately 6,000 base pairs long and consists of two non-overlapping open reading frames (ORF) which are flanked by UTR and target site duplications.
First ORF
The first ORF encodes a RNA-binding protein of 500 amino acid lengths that weighs 40 kDA. This protein contains a leucine zipper motif and functions as a chaperone.
Second ORF
The second ORF of the L1 encodes a protein-complex that has endonuclease and reverse transcriptase activity. The encoded protein has a molecular weight of 150 kDA.
UTR
The 5' Untranslated region (UTR) of the L1 element contains a strong, internal RNA Polymerase II transcription promoter in sense and a less strong anti-sense promoter.