Cer4 is a LTR retrotransposon described from sequencing data in the chromosome X of C. elegans (Bowen and McDonald 1999). Cer4 belongs, along with other LTR retrotransposons, to Mag a large Ty3/Gypsy cluster widely distributed in both protostomes and deuterostomes (for more details, see Malik and Eickbush 1999; Volff et al. 2001; Tubio, Naveira and Costas 2004). The genomic structure of this element is 5.1 Kb in size including LTRs of 165 nt. The internal region displays a Primer Binding Site (PBS) complementary to a tRNASer, a single Open Reading Frame (ORF) gag-pol that presents a frameshifting between the capsid (CA) and the nucleocapsid (NC) domains (not detailed in the figure below), and a Polypurine Tract (PPT) adjacent to the 3´LTR (Bowen and McDonald 1999; Ganko, Fielman and McDonald 2001).
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