In mammals,transcriptional activity of some genes is correlated with their location on loops that exit the chromosome territories(55).These loops are proposed to bring genes into contact with transcriptional factories or juxtapose coregulated genes.because of the high gene density of trypanosome MBCs and their polycistronic transcription and posttranscriptional mode of regulation,such models are unlikely to be extensible from mammals to trypanosomes.