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. a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Interacts with MOV10. Long interspersed element-1/LINE-1/L1 retrotransposons are present in more than 500'000 full (6 kb) or truncated copies in the human genome. Most of them are inactive but one estimate is that 80 to 100 of those elements could be transcribed, translated and active in any individual. An active LINE-1 encodes for 2 proteins translated from a single RNA containing two non-overlapping ORFs, ORF1 and ORF2. ORF2p is described in this entry as a representative of all ORF2p potentially expressed by active elements. ORF1p is described in the related entry AC Q9UN81.