Enhancement of telomere-plasmid segregation by the X-telomere associated sequence in Saccharomyces cerevisiae involves SIR2, SIR3, SIR4 and ABF1.
We have previously shown that circular replicating plasmids that carry yeast telomere repeat sequence (TG1-3) tracts segregate efficiently relative to analogous plasmids lacking the TG1-3 tract and this efficient segregation is dependent upon RAP1. While a long TG1-3 tract is sufficient to improve plasmid segregation, the segregation efficiency of telomere plasmids (TEL-plasmids) is enhanced when the X-Telomere Associated Sequence (X-TAS) is also included on the plasmids. We now demonstrate that the enhancement of TEL-plasmid segregation by the X-TAS depends on SIR2, SIR3, SIR4 and ABF1 in trans and requires the Abf1p-binding site within the X-TAS. Mutation of the Abf1p-binding site within the X-TAS results in TEL-plasmids that are no longer affected by mutations in SIR2, SIR3 or SIR4, despite the fact that other Abf1p-binding sites are present on the plasmid. Mutation of the ARS consensus sequence within the X-TAS converts the X-TAS from an enhancer element to a negative element that interferes with TEL-plasmid segregation in a SIR-dependent manner. Thus, telomere associated sequences interact with TG1-3 tracts on the plasmid, suggesting that the TASs have an active role in modulating telomere function.
Enomoto
S
S
Department of Plant Biology, University of Minnesota, St. Paul 55108.
Longtine
M S
MS
Berman
J
J
D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D004274:DNA, Recombinant / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D016615:Telomere / Q000378:metabolism*
D004271:DNA, Fungal; D004274:DNA, Recombinant