7n94
LINE-1 endonuclease domain complex with DNA
Structural highlights
FunctionLORF2_HUMAN Has a reverse transcriptase activity required for target-primed reverse transcription of the LINE-1 element mRNA, a crucial step in LINE-1 retrotransposition. Has also an endonuclease activity that allows the introduction of nicks in the chromosomal target DNA. Cleaves DNA in AT-rich regions between a 5' stretch of purines and a 3' stretch of pyrimidines, corresponding to sites of LINE-1 integration in the genome.[1] [2] [3] Publication Abstract from PubMedLong interspersed nuclear element-1 (L1) is an autonomous non-LTR retrotransposon comprising approximately 20% of the human genome. L1 self-propagation causes genomic instability and is strongly associated with aging, cancer and other diseases. The endonuclease domain of L1's ORFp2 protein (L1-EN) initiates de novo L1 integration by nicking the consensus sequence 5'-TTTTT/AA-3'. In contrast, related nucleases including structurally conserved apurinic/apyrimidinic endonuclease 1 (APE1) are non-sequence specific. To investigate mechanisms underlying sequence recognition and catalysis by L1-EN, we solved crystal structures of L1-EN complexed with DNA substrates. This showed that conformational properties of the preferred sequence drive L1-EN's sequence-specificity and catalysis. Unlike APE1, L1-EN does not bend the DNA helix, but rather causes 'compression' near the cleavage site. This provides multiple advantages for L1-EN's role in retrotransposition including facilitating use of the nicked poly-T DNA strand as a primer for reverse transcription. We also observed two alternative conformations of the scissile bond phosphate, which allowed us to model distinct conformations for a nucleophilic attack and a transition state that are likely applicable to the entire family of nucleases. This work adds to our mechanistic understanding of L1-EN and related nucleases and should facilitate development of L1-EN inhibitors as potential anticancer and antiaging therapeutics. Structural dissection of sequence recognition and catalytic mechanism of human LINE-1 endonuclease.,Miller I, Totrov M, Korotchkina L, Kazyulkin DN, Gudkov AV, Korolev S Nucleic Acids Res. 2021 Sep 23. pii: 6374484. doi: 10.1093/nar/gkab826. PMID:34554261[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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