A retroposon in the 5' flank of a Trypanosoma brucei VSG gene lacks insertional terminal repeats.

A retroposon-like repeated sequence, ingi, occurs in high copy number in the genome of Trypanosoma brucei brucei. An ingi is present in the 5' flank of the 5C gene, an intrachromosomal IsTat 1.5 variant surface glycoprotein (VSG) gene family member. The 5' end of the ingi is located 22 bp upstream of the putative VSG start codon and the ingi open reading frame is in the opposite orientation to that of the VSG gene. The termini of the ingi are not flanked by a short repeat sequence and there are no sequences upstream of the ingi insertion which are homologous to the 5' flanking sequence of other 5 VSG gene family members. Thus, it appears that recombination and/or gene conversion between two ingi sequences may have eliminated the original 5C gene flanking sequence. Similar events may also have occurred with all but one previously reported ingi.