Nucleic acid-binding protein which is essential for retrotransposition of LINE-1 elements in the genome. Functions as a nucleic acid chaperone binding its own transcript and therefore preferentially mobilizing the transcript from which they are encoded. Homotrimer (via coiled coil domain). May also form larger homooligomers. May interact with DDX39A, HNRNPA1, SERBP1 and YBX1. Interacts with TEX19 and UBR2 (PubMed:28806172). Interacts with MOV10 (PubMed:23093941). Interacts with APOBEC3D; this interaction inhibits LINE-1 retrotransposition (PubMed:27428332). Colocalizes with its encoding RNA in cytoplasmic ribonucleoprotein particle (PubMed:16183655). Mainly cytoplasmic, rarely detected in the nucleus, possibly within the nucleolus (PubMed:17562864). The coiled coil domain mediates homotrimerization. The RRM and the CTD domain are both required for proper RNA-binding activity. Polyubiquitinated, probably by UBR2, which induces its degradation. 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 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 2 non-overlapping ORFs, ORF1 and ORF2. ORF1p is described in this entry as a representative of all ORF1p potentially expressed by active elements. ORF2p is described in the related entry AC O00370. Belongs to the transposase 22 family.