TY - JOUR
T1 - Tandemly repeated DNA is a target for the partial replacement of thymine by β-d-glucosyl-hydroxymethyluracil in Trypanosoma brucei
AU - van Leeuwen, Fred
AU - Kieft, Rudo
AU - Cross, Mike
AU - Borst, Piet
PY - 2000
Y1 - 2000
N2 - In the DNA of African trypanosomes a small fraction of thymine is replaced by the modified base β-d-glucosyl-hydroxymethyluracil (J). The function of this large base is unknown. The presence of J in the silent variant surface glycoprotein gene expression sites and the lack of J in the transcribed expression site indicates that DNA modification might play a role in control of gene repression. However, the abundance of J in the long telomeric repeat tracts and in subtelomeric arrays of simple repeats suggests that J may also have specific functions in repetitive DNA. We have now analyzed chromosome-internal repetitive sequences in the genome of Trypanosoma brucei and found J in the minichromosomal 177-bp repeats, in the long arrays of 5S RNA gene repeats, and in the spliced-leader RNA gene repeats. No J was found in the rDNA locus or in dispersed repetitive transposon-like elements. Remarkably, the rDNA of T. brucei is not organized in long arrays of tandem repeats, as in many other eukaryotes. T. brucei contains only ~15-20 rDNA repeat units that are divided over six to seven chromosomes. Our results show that J is present in many tandemly repeated sequences, either at a telomere or chromosome internal. The presence of J might help to stabilize the long arrays of repeats in the genome. (C) 2000 Elsevier Science B.V.
AB - In the DNA of African trypanosomes a small fraction of thymine is replaced by the modified base β-d-glucosyl-hydroxymethyluracil (J). The function of this large base is unknown. The presence of J in the silent variant surface glycoprotein gene expression sites and the lack of J in the transcribed expression site indicates that DNA modification might play a role in control of gene repression. However, the abundance of J in the long telomeric repeat tracts and in subtelomeric arrays of simple repeats suggests that J may also have specific functions in repetitive DNA. We have now analyzed chromosome-internal repetitive sequences in the genome of Trypanosoma brucei and found J in the minichromosomal 177-bp repeats, in the long arrays of 5S RNA gene repeats, and in the spliced-leader RNA gene repeats. No J was found in the rDNA locus or in dispersed repetitive transposon-like elements. Remarkably, the rDNA of T. brucei is not organized in long arrays of tandem repeats, as in many other eukaryotes. T. brucei contains only ~15-20 rDNA repeat units that are divided over six to seven chromosomes. Our results show that J is present in many tandemly repeated sequences, either at a telomere or chromosome internal. The presence of J might help to stabilize the long arrays of repeats in the genome. (C) 2000 Elsevier Science B.V.
UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0033839259&origin=inward
UR - https://www.ncbi.nlm.nih.gov/pubmed/10960172
U2 - https://doi.org/10.1016/S0166-6851(00)00247-4
DO - https://doi.org/10.1016/S0166-6851(00)00247-4
M3 - Article
C2 - 10960172
SN - 0166-6851
VL - 109
SP - 133
EP - 145
JO - Molecular and Biochemical Parasitology
JF - Molecular and Biochemical Parasitology
IS - 2
ER -