TY - JOUR
T1 - Partitioning of the 2-μm circle plasmid of Saccharomyces cerevisiae
T2 - Functional coordination with chromosome segregation and plasmid-encoded Rep protein distribution
AU - Velmurugan, Soundarapandian
AU - Yang, Xian Mei
AU - Chan, Clarence S.M.
AU - Dobson, Melanie
AU - Jayaram, Makkuni
PY - 2000/5/1
Y1 - 2000/5/1
N2 - The efficient partitioning of the 2-μm plasmid of Saccharomyces cerevisiae at cell division is dependent on two plasmid-encoded proteins (Rep1p and Rep2p), together with the cis-acting locus REP3 (STB). In addition, host encoded factors are likely to contribute to plasmid segregation. Direct observation of a 2-μm-derived plasmid in live yeast cells indicates that the multiple plasmid copies are located in the nucleus, predominantly in clusters with characteristic shapes. Comparison to a single- tagged chromosome or to a yeast centromeric plasmid shows that the segregation kinetics of the 2-μm plasmid and the chromosome are quite similar during the yeast cell cycle. Immunofluorescence analysis reveals that the plasmid is colocalized with the Rep1 and Rep2 proteins within the yeast nucleus. Furthermore, the Rep proteins (and therefore the plasmid) tend to concentrate near the poles of the yeast mitotic spindle. Depolymerization of the spindle results in partial dispersion of the Rep proteins in the nucleus concomitant with a loosening in the association between plasmid molecules. In an ipl1-2 yeast strain, shifted to the nonpermissive temperature, the chromosomes and plasmid almost always missegregate in tandem. Our results suggest that, after DNA replication, plasmid distribution to the daughter cells occurs in the form of specific DNA-protein aggregates. They further indicate that the plasmid partitioning mechanism may exploit at least some of the components of the cellular machinery required for chromosomal segregation.
AB - The efficient partitioning of the 2-μm plasmid of Saccharomyces cerevisiae at cell division is dependent on two plasmid-encoded proteins (Rep1p and Rep2p), together with the cis-acting locus REP3 (STB). In addition, host encoded factors are likely to contribute to plasmid segregation. Direct observation of a 2-μm-derived plasmid in live yeast cells indicates that the multiple plasmid copies are located in the nucleus, predominantly in clusters with characteristic shapes. Comparison to a single- tagged chromosome or to a yeast centromeric plasmid shows that the segregation kinetics of the 2-μm plasmid and the chromosome are quite similar during the yeast cell cycle. Immunofluorescence analysis reveals that the plasmid is colocalized with the Rep1 and Rep2 proteins within the yeast nucleus. Furthermore, the Rep proteins (and therefore the plasmid) tend to concentrate near the poles of the yeast mitotic spindle. Depolymerization of the spindle results in partial dispersion of the Rep proteins in the nucleus concomitant with a loosening in the association between plasmid molecules. In an ipl1-2 yeast strain, shifted to the nonpermissive temperature, the chromosomes and plasmid almost always missegregate in tandem. Our results suggest that, after DNA replication, plasmid distribution to the daughter cells occurs in the form of specific DNA-protein aggregates. They further indicate that the plasmid partitioning mechanism may exploit at least some of the components of the cellular machinery required for chromosomal segregation.
KW - BRN1
KW - Mitotic spindle
KW - Plasmid cohesion
KW - Tubulin
KW - ipl1-2 mutation
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U2 - 10.1083/jcb.149.3.553
DO - 10.1083/jcb.149.3.553
M3 - Article
C2 - 10791970
AN - SCOPUS:0034178249
SN - 0021-9525
VL - 149
SP - 553
EP - 566
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 3
ER -