A Silenced Plasmodium falciparum var Promoter Can Be Activated In Vivo through Spontaneous Deletion of a Silencing Element in the Intron

Introns of Plasmodium falciparum var genes act as transcriptional silencing elements that help control antigenic variations. In transfected episomes, intron silencing of a drug-selectable marker under var promoter control is reversed by the spontaneous deletion of key intron regions. The resulting promoter activation does not affect the transcription of chromosomal var genes.