Previous Article | Next Article ![]()
Molecular and Cellular Biology, December 1999, p. 8083-8093, Vol. 19, No. 12
Department of Molecular Biology, Princeton
University, Princeton, New Jersey 08544
Received 24 May 1999/Returned for modification 29 June
1999/Accepted 25 August 1999
Many Saccharomyces telomeres bear one or more copies of
the repetitive Y' element followed by ~350 bp of telomerase-generated C1-3A/TG1-3 repeats. Although most cells
lacking a gene required for the telomerase pathway die after 50 to 100 cell divisions, survivors arise spontaneously in such cultures. These survivors have one of two distinct patterns of telomeric DNA (V. Lundblad and E. H. Blackburn, Cell 73:347-360, 1993). The more common of the two patterns, seen in type I survivors, is tandem amplification of Y' followed by very short tracts of
C1-3A/TG1-3 DNA. By determining the structure
of singly tagged telomeres, chromosomes in type II survivors were shown
to end in very long and heterogeneous-length tracts of
C1-3A/TG1-3 DNA, with some telomeres having
12 kb or more of C1-3A/TG1-3 repeats.
Maintenance of these long telomeres required the continuous presence of
Rad52p. Whereas type I survivors often converted to the type II
structure of telomeric DNA, the type II pattern was maintained for at
least 250 cell divisions. However, during outgrowth, the structure of
type II telomeres was dynamic, displaying gradual shortening as well as
other structural changes that could be explained by continuous gene
conversion events with other telomeres. Although most type II survivors
had a growth rate similar to that of telomerase-proficient cells, their
telomeres slowly returned to wild-type lengths when telomerase was
reintroduced. The very long and heterogeneous-length telomeres
characteristic of type II survivors in Saccharomyces are
reminiscent of the telomeres in immortal human cell lines and tumors
that maintain telomeric DNA in the absence of telomerase.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Telomere-Telomere Recombination Is an Efficient
Bypass Pathway for Telomere Maintenance in Saccharomyces
cerevisiae
*
Corresponding author. Mailing address: Department of
Molecular Biology, Princeton University, Princeton, NJ 08544. Phone: (609) 258-6770. Fax: (609) 258-1701. E-mail:
vzakian{at}molbio.princeton.edu.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|