TY - JOUR
T1 - Intramitochondrial localization of universal minicircle sequence-binding protein, a trypanosomatid protein that binds kinetoplast minicircle replication origins
AU - Abu-Elneel, Kawther
AU - Robinson, Derrick R.
AU - Drew, Mark E.
AU - Englund, Paul T.
AU - Shlomai, Joseph
PY - 2001/5/14
Y1 - 2001/5/14
N2 - Kinetoplast DNA (kDNA), the mitochondrial DNA of the trypanosomatid Crithidia fasciculata, is a unique structure containing 5,000 DNA minicircles topologically linked into a massive network. In vivo, the network is condensed into a disk-shaped structure. Replication of minicircles initiates at unique origins that are bound by universal minicircle sequence (UMS)-binding protein (UMSBP), a sequence-specific DNA-binding protein. This protein, encoded by a nuclear gene, localizes within the cell's single mitochondrion. Using immunofluorescence, we found that UMSBP localizes exclusively to two neighboring sites adjacent to the face of the kDNA disk nearest the cell's flagellum. This site is distinct from the two antipodal positions at the perimeter of the disk that is occupied by DNA polymerase β, topoisomerase II, and a structure-specific endonuclease. Although we found constant steady-state levels of UMSBP mRNA and protein and a constant rate of UMSBP synthesis throughout the cell cycle, immunofluorescence indicated that UMSBP localization within the kinetoplast is not static. The intramitochondrial localization of UMSBP and other kDNA replication enzymes significantly clarifies our understanding of the process of kDNA replication.
AB - Kinetoplast DNA (kDNA), the mitochondrial DNA of the trypanosomatid Crithidia fasciculata, is a unique structure containing 5,000 DNA minicircles topologically linked into a massive network. In vivo, the network is condensed into a disk-shaped structure. Replication of minicircles initiates at unique origins that are bound by universal minicircle sequence (UMS)-binding protein (UMSBP), a sequence-specific DNA-binding protein. This protein, encoded by a nuclear gene, localizes within the cell's single mitochondrion. Using immunofluorescence, we found that UMSBP localizes exclusively to two neighboring sites adjacent to the face of the kDNA disk nearest the cell's flagellum. This site is distinct from the two antipodal positions at the perimeter of the disk that is occupied by DNA polymerase β, topoisomerase II, and a structure-specific endonuclease. Although we found constant steady-state levels of UMSBP mRNA and protein and a constant rate of UMSBP synthesis throughout the cell cycle, immunofluorescence indicated that UMSBP localization within the kinetoplast is not static. The intramitochondrial localization of UMSBP and other kDNA replication enzymes significantly clarifies our understanding of the process of kDNA replication.
KW - KDNA replication
KW - Kinetoplast DNA
KW - UMS-binding protein
KW - Universal minicircle sequence
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U2 - 10.1083/jcb.153.4.725
DO - 10.1083/jcb.153.4.725
M3 - Article
C2 - 11352934
AN - SCOPUS:0035858881
SN - 0021-9525
VL - 153
SP - 725
EP - 733
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 4
ER -