Cer7 is a LTR retrotransposon found in the genome of the nematode Caenorhabditis elegans (Bowen and McDonald 1999). This element belongs to the Tas clade (Copeland et al. 2005) within Branch 1 of the Bel/Pao family (Llorens et al. 2009).
The genome of Cer7 is about of 10 Kb in size (10062 bp long), including LTRs of 470 (5’LTR) and 327 nts (3’LTR). The size difference between both LTRs is due to an insertion of 143 nts within 5’LTR sequence. Although the internal coding region is disrupted by several stop codons and frameshiftings, the distinct gag and pol domains typical of LTR retrotransposons are clearly evident in the sequence of this element. Cer7 also codifies for an env-like gene at its C-terminal translated region(Bowen and McDonald 1999). We found another extra gag-like ORF of 396 amino acids codified by the 8528 and 9718 nts region of Cer7, which contains the typical capsid and nucleocapsid motifs of Bel/Pao gags. A similar feature has been observed in the genome of another Bel/Pao element called Max.
Figure not to scale. If present, long terminal repeats (LTRs) have been highlighted in blue. Amino acid motifs noted with lines indicate the conserved residues in each protein domain, abbreviations below mean:
||DU or DUT=dUTPase
||TAV or IBMP=transactivator/viroplasmin or inclusion body matrix protein
||PBS=primer binding site
||ATF=aphid transmission factor
||VAP=virion associated protein