The carboxy-terminal segment of the human LINE-1 ORF2 protein is involved in RNA binding

• The 180-aa C-terminal segment (CTS) of human L1 ORF2p was expressed and purified from bacteria.
• The nucleic acid binding properties of the CTS of L1ORF2p were examined in vitro.
• The CTS of L1 ORF2p is an RNA binding domain.
• The CTS of L1 ORF2p binds RNA in non-sequence-specific manner in the low nanomolar range.
• Disruption of the putative Zn-knuckle structure does not significantly affect RNA binding.

The human LINE-1/L1 ORF2 protein is a multifunctional enzyme which plays a vital role in the life cycle of the human L1 retrotransposon. The protein consists of an endonuclease domain, followed by a central reverse transcriptase domain and a carboxy-terminal C-domain with unknown function. Here, we explore the nucleic acid binding properties of the 180-amino acid carboxy-terminal segment (CTS) of the human L1 ORF2p in vitro. In a series of experiments involving gel shift assay, we demonstrate that the CTS of L1 ORF2p binds RNA in non-sequence-specific manner. Finally, we report that mutations destroying the putative Zn-knuckle structure of the protein do not significantly affect the level of RNA binding and discuss the possible functional role of the CTS in L1 retrotransposition.