Dr. Robinson et K. Gull, THE CONFIGURATION OF DNA-REPLICATION SITES WITHIN THE TRYPANOSOMA-BRUCEI KINETOPLAST, The Journal of cell biology, 126(3), 1994, pp. 641-648
The kinetoplast is a concatenated network of circular DNA molecules fo
und in the mitochondrion of many trypanosomes. This mass of DNA is rep
licated in a discrete ''S'' phase in the cell cycle. We have tracked t
he incorporation of the thymidine analogue 5-bromodeoxyuridine into ne
wly replicated DNA by immunofluorescence and novel immunogold labeling
procedures. This has allowed the detection of particular sites of rep
licated DNA in the replicating and segregating kinetoplast. These stud
ies provide a new method for observing kinetoplast DNA (kDNA) replicat
ion patterns at high resolution. The techniques reveal that initially
the pattern of replicated DNA is antipodal and can be detected both on
isolated complexes and in replicating kDNA in vivo. In Trypanosoma br
ucei the opposing edges of replicating kDNA never extend around the co
mplete circumference of the network, as seen in other kinetoplastids.
Furthermore, crescent-shaped labeling patterns are formed which give w
ay to labeling of most of the replicating kDNA except the characterist
ic midzone. The configuration of these sites of replicated DNA molecul
es is different to previous studies on organisms such as Crithidia fas
ciculata, suggesting differences in the timing of replication of mini
and maxicircles and/or organization of the replicative apparatus in th
e kinetoplast of the African trypanosome.