Mdg1 is a LTR retrotransposon described in Drosophila melanogaster (Ilyin et al. 1980a; 1980b; Kulguskin, Ilyin and Georgiev 1981; Avedisov, Cherkasova and Il'in,Iu. 1990). Mdg1 is similar to 412 and belongs to 412/mdg1 clade (Malik and Eickbush1999). Phylogenetic analyses suggest that this clade is closely related to errantiviruses. 412/mdg1 integrases have been related to a single copy gene which codifies for a putative integrase protein (GIN-1) in humans and other vertebrates (Lloréns and Marín 2001). The genomic structure of mg1 is 7.4 Kb in size including LTRs of 442 nt. The internal region displays a Primer Binding Site (PBS) complementary to a tRNALys, two Open Reading Frames (ORFs) for gag and pol genes, and a Polypurine Tract (PPT) adjacent to the 3´LTR (Avedisov, Cherkasova and Il'in,Iu. 1990).
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