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J‐binding protein increases the level and retention of the unusual base J in trypanosome DNA
Author(s) -
Cross Mike,
Kieft Rudo,
Sabatini Robert,
DirksMulder Anita,
Chaves Inês,
Borst Piet
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.03144.x
Subject(s) - biology , thymine , dna , trypanosoma brucei , gene , biochemistry , base pair , microbiology and biotechnology , repeated sequence , nuclear dna , genome , mitochondrial dna
Summary The nuclear DNA of Trypanosoma brucei and other kinetoplastid flagellates contains the unusual base β‐ d ‐glucosyl‐hydroxymethyluracil, called J, replacing part of the thymine in repetitive sequences. We have described a 100 kDa protein that specifically binds to J in duplex DNA. We have now disrupted the genes for this J‐binding protein (JBP) in T. brucei . The disruption does not affect growth, gene expression or the stability of some repetitive DNA sequences. Unexpectedly, however, the JBP KO trypanosomes contain only about 5% of the wild‐type level of J in their DNA. Excess J, randomly introduced into T. brucei DNA by growing the cells in the presence of the J precursor 5‐hydroxymethyldeoxyuridine, is lost by simple dilution as the KO trypanosomes multiply, showing that JBP does not protect J against removal. In contrast, cells containing JBP lose excess J only sluggishly. We conclude that JBP is able to activate the thymine modification enzymes to introduce additional J in regions of DNA already containing a basal level of J. We propose that JBP is a novel DNA modification maintenance protein.