Structural features and mechanism of translocation of non-LTR retrotransposons in Candida albicans

A number of abundant mobile genetic elements called retrotransposons reverse transcribe RNA to generate DNA for insertion into eukaryotic genomes. Non-long-terminal repeat (non-LTR) retrotransposons represent a major class of retrotransposons, and transposons that move by target-primed reverse transcription lack LTRs characteristic of retroviruses and retroviral-like transposons. Yeast model systems in Candida albicans and Saccharomyces cerevisiae have been developed for the study of non-LTR retrotransposons. Non-LTR retrotransposons are divided into LINEs (long interspersed nuclear elements), SINEs (short interspersed nuclear elements), and SVA (SINE, VNTR, and Alu). LINE-1 elements have been described in fungi, and several families called Zorro elements have been detected from C. albicans. They are all members of L1 clades. Through a mechanism named target-primed reverse transcription (TPRT), LINEs translocate the new copy into the target site to initiate DNA synthesis primed by the 3′ OH of the broken strand. In this article, we describe some advances in the research on structural features and origin of non-LTR retrotransposons in C. albicans, and discuss mechanisms underlying their reverse transcription and integration of the donor copy into the target site.