BETA-D-GLUCOSYL-HYDROXYMETHYLURACIL - A NOVEL MODIFIED BASE PRESENT IN THE DNA OF THE PARASITIC PROTOZOAN TRYPANOSOMA-BRUCEI

We have previously shown that the DNA of the unicellular eukaryote T. brucei contains about 0.1% of a novel modified base, called J. The pre sence of J correlates with a DNA modification associated with the sile ncing of telomeric expression sites for the variant surface antigens o f trypanosomes. Here we show that J is 5-((beta-D-glucopyranosyloxy)-m ethyl)-uracil (shortened to beta-D-glucosyl-hydroxymethyluracil), a ba se not previously found in DNA. We discuss putative pathways for the i ntroduction of this base modification at specific positions in the DNA and the possible contribution of this modification to repression of s urface antigen gene expression.