Tat is a LTR retroelement originally characterized in the genome of Arabidopsis thaliana as an insertion sequence close to the SAM1 gene (Peleman et al.1991). This element belongs to a lineage of plant LTR retrotransposons (Tat), sibling of other lineage of putative plant endogenous retroviruses (Athila), providing evidence of a shared ancestral lineage originally described as class A by Wright and Voytas (1998). Tat has several subtypes, subtype Tat4-1 is taken as representative. The genome of this clon is 11.9 Kb in size including LTRs of 450 nt. The internal region displays a Primer Binding Sites (PBS) complementary to a tRNAArg, two Open Reading Frames (ORFs) for gag and pol genes, a non-coding zone of 5.1 Kb downstream to the integrase domain, and also, a Polypurine Tract (PPT) adjacent to the 3′LTR (Wright and Voytas 1998).
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