Final answer:
Non-LTR retrotransposons such as LINES encode specific proteins including reverse transcriptase and endonuclease/integrase which enable autonomous transposition without the retroviral envelope.
Step-by-step explanation:
Non-LTR retrotransposons, specifically LINES (Long Interspersed Nuclear Elements), encode unique proteins that facilitate their transposition. These proteins include a reverse transcriptase encoded by the RT gene, an endonuclease and integrase encoded by the ORF2 gene within the element. The Gag protein, encoded by the Gag gene, is involved in the formation of virus-like particles, although it is not enveloped as with retroviruses. Crucially, LINES can mobilize autonomously due to these encoded enzymes, as opposed to SINEs (Short Interspersed Nuclear Elements) which require enzymes encoded by other elements for their transposition.