Base J or beta-d-glucosylhydroxymethyluracil is a DNA modification replacing a 
fraction of thymine in the nuclear DNA of kinetoplastid parasites and of 
Euglena. J is located in the telomeric sequences of Trypanosoma brucei and in 
other simple repeat DNA sequences. In addition, J was found in the inactive 
variant surface glycoprotein (VSG) expression sites, but not in the active 
expression site of T. brucei, suggesting that J could play a role in 
transcription silencing in T. brucei. We have now looked at the distribution of 
J in the genomes of other kinetoplastid parasites. First, we analyzed the DNA 
sequences immunoprecipitated with a J-antiserum in Leishmania major Friedlin. 
Second, we investigated the co-migration of J- and telomeric repeat-containing 
DNA sequences of various kinetoplastids using J-immunoblots and Southern blots 
of fragmented DNA. We find only approximately 1% of J outside the telomeric 
repeat sequences of Leishmania sp. and Crithidia fasciculata, in contrast to the 
substantial fraction of non-telomeric J found in T. brucei, Trypanosoma 
equiperdum and Trypanoplasma borreli. Our results suggest that J is a telomeric 
base modification, recruited for other (unknown) functions in some 
kinetoplastids and Euglena.