β-D-Glucopyranosyloxymethyluracil or base J is a hypermodified
nucleobase found in the
DNA of kinetoplastids including the human
pathogenic trypanosomes. It was discovered in 1993, in the trypanosome
Trypanosoma brucei and was the first hypermodified nucleobase found in
eukaryotic DNA; it has since been found in other kinetoplastids,
including Leishmania. Within these organism
Base J acts as a RNA
polymerase II transcription terminator, with its removal in knockout
cells being accompanied by a massive read-through at RNA polymerase II
termination sites, which ultimately proves lethal to the cell.
Base J is formed by the initial hydroxylation of thymidine and the
subsequent glycosylation by an as yet unidentified
The biosynthesis of base J. A: thymidine hydroxylase; B:
beta-glucosyltranferase; 1: dT (desoxy thymidine); 2: HOCH3dU; 3: dJ
^ a b Borst, Piet; Sabatini, Robert (October 2008). "Base J:
Discovery, Biosynthesis, and Possible Functions". Annual Review of
Microbiology. 62 (1): 235–251.
doi:10.1146/annurev.micro.62.081307.162750. PMID 18729733.
^ van Luenen, Henri G.A.M.; Farris, Carol; Jan, Sabrina; Genest,
Paul-Andre; Tripathi, Pankaj; Velds, Arno; Kerkhoven, Ron M.;
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Heidebrecht, Tatjana; Perrakis, Anastassis; Pagie, Ludo; van Steensel,
Bas; Myler, Peter J.; Borst, Piet (August 2012). "Glucosylated
DNA Base J, Prevents Transcriptional Readthrough
in Leishmania". Cell. 150 (5): 909–921.
doi:10.1016/j.cell.2012.07.030. PMC 3684241 .
^ Hazelbaker, Dane Z.; Buratowski, Stephen (November 2012).
Base J Blocks the Way". Current Biology. 22 (22):
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