Disruption of the Crithidia fasciculata KAP1 gene results in structural rearrangement of the kinetoplast disc.

The mitochondrial DNA (kinetoplast DNA) in trypanosomatids exists as a highly organized nucleoprotein structure with the DNA consisting of thousands of interlocked circles. Four H1 histone-like proteins (KAP1, 2, 3 and 4) are associated with the kinetoplast DNA in the trypanosomatid Crithidia fasciculata. We have disrupted both alleles of the KAP1 gene in this diploid protozoan and shown that expression of the KAP1 protein is eliminated. The mutant strain is viable but has substantial rearrangement of the kinetoplast structure. Expression of the KAP1 protein from an episome restored expression of the KAP1 protein in the mutant strain and also restored a normal kinetoplast structure. These studies provide evidence that the KAP1 protein is involved in kinetoplast DNA organization in vivo but is nonessential for cell viability.