Introduction of extra telomeric DNA sequences into Saccharomyces cerevisiae results in telomere elongation.
The termini of Saccharomyces cerevisiae chromosomes consist of tracts of C1-3A (one to three cytosine and one adenine residue) sequences of approximately 450 base pairs in length. To gain insights into trans-acting factors at telomeres, high-copy-number linear and circular plasmids containing tracts of C1-3A sequences were introduced into S. cerevisiae. We devised a novel system to distinguish by color colonies that maintained the vector at 1 to 5, 20 to 50, and 100 to 400 copies per cell and used it to change the amount of telomeric DNA sequences per cell. An increase in the number of C1-3A sequences caused an increase in the length of telomeric C1-3A repeats that was proportional to plasmid copy number. Our data suggest that telomere growth is inhibited by a limiting factor(s) that specifically recognizes C1-3A sequences and that this factor can be effectively competed for by long tracts of C1-3A sequences at telomeres or on circular plasmids. Telomeres without this factor are exposed to processes that serve to lengthen chromosome ends.
Runge
K W
KW
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Zakian
V A
VA
D001483:Base Sequence; D002875:Chromosomes / Q000648:ultrastructure*; D004271:DNA, Fungal / Q000235:genetics*; D005784:Gene Amplification; D005822:Genetic Vectors; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000648:ultrastructure
D004271:DNA, Fungal