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Molecular and Cellular Biology, October 2001, p. 6559-6573, Vol. 21, No. 19
Department of Biochemistry, Tulane University
Health Sciences Center, New Orleans, Louisiana 70112
Received 12 February 2001/Returned for modification 12 March
2001/Accepted 22 June 2001
We have previously identified a process in the yeast
Saccharomyces cerevisiae that results in the contraction
of elongated telomeres to wild-type length within a few generations. We
have termed this process telomeric rapid deletion (TRD). In
this study, we use a combination of physical and genetic assays to
investigate the mechanism of TRD. First, to distinguish among several
recombinational and nucleolytic pathways, we developed a novel physical
assay in which HaeIII restriction sites are positioned
within the telomeric tract. Specific telomeres were
subsequently tested for HaeIII site movement between
telomeres and for HaeIII site retention during TRD.
Second, genetic analyses have demonstrated that mutations in
RAD50 and MRE11 inhibit TRD. TRD,
however, is independent of the Rap1p C-terminal domain, a central
regulator of telomere size control. Our results provide evidence that
TRD is an intrachromatid deletion process in which sequences near the
extreme terminus invade end-distal sequences and excise the intervening
sequences. We propose that the Mre11p-Rad50p-Xrs2p complex prepares the
invading telomeric overhang for strand invasion, possibly
through end processing or through alterations in chromatin structure.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.19.6559-6573.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Intrachromatid Excision of Telomeric DNA as a
Mechanism for Telomere Size Control in Saccharomyces
cerevisiae


*
Corresponding author. Mailing address: Tulane
University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA
70112. Phone: (504) 584-3688. Fax: (504) 584-2739. E-mail:
alustig{at}mailhost.tcs.tulane.edu.
Dedicated to E. B. Hoffman.
Present address: Institute of Biochemistry and Biophysics, Polish
Academy of Sciences, 020106, Warsaw, Poland.
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