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. 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 that entry as a representative of all ORF2p potentially expressed by active elements in mouse genome. ORF1p is described in the related entry AC P11260.