The IsTat 1.3 VSG multigene family inTrypanosoma bruceui: retention of the expression linked copy through multiple antigenic switches

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Abstract
In the IsTaR 1 serodeme of T. brucei the 3 variant surface glycoprotein (VSG) gene family contains about 10 members, one of which has a telomeric location on a minichromosome. The expression linked copy (ELC) of the 3 VSG gene which occurs in an antigenic variant expressing the 3 VSG, also has a telomeric location but unlike the minichromosomal 3 VSG gene has restriction sites upstream from the 5' barren region. This ELC is retained on the same telomere in a subsequent variant that expresses a telomeric 7 VSG ELC and in relapse variants and procyclic forms derived from variant antigenic types (VATs) 3 and 7. The 7 ELC has a restriction map upstream from the 5' barren region that differs from, but is similar to, that of the 3 ELC. These data indicate that the 3 and 7 ELCs are on different telomeres when expressed.