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Endonuclease domain (L1-EN) of the non-LTR retrotransposon LINE-1 (L1), and related domains This family contains the endonuclease domain (L1-EN) of the non-LTR retrotransposon LINE-1 (L1), and related domains, including the endonuclease of Xenopus laevis Tx1. These retrotranspons belong to the subtype 2, L1-clade. LINES can be classified into two subtypes. Subtype 2 has two ORFs: the second (ORF2) encodes a modular protein consisting of an N-terminal apurine/apyrimidine endonuclease domain (EN), a central reverse transcriptase, and a zinc-finger-like domain at the C-terminus. LINE-1/L1 elements (full length and truncated) comprise about 17% of the human genome. This endonuclease nicks the genomic DNA at the consensus target sequence 5'TTTT-AA3' producing a ribose 3'-hydroxyl end as a primer for reverse transcription of associated template RNA. This subgroup also includes the endonuclease of Xenopus laevis Tx1, another member of the L1-clade. This family belongs to the large EEP (exonuclease/endonuclease/phosphatase) superfamily that contains functionally diverse enzymes that share a common catalytic mechanism of cleaving phosphodiester bonds. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",