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Mol. Cell. Biol., 03 1996, 1267-1274, Vol 16, No. 3
Q Fan and M Yao
Programmed chromosome breakage occurs in many ciliated protozoa and is
accompanied by efficient new telomere formation. In this study, we have
investigated the relationship between programmed chromosome breakage and
telomere formation in Tetrahymena thermophila. Using specially constructed
DNA clones containing the breakage signal Cbs in transformation studies, we
have determined the locations of telomere addition around the breakage
sites. They occur at variable positions, over 90% of which are within a
small region (less than 30 bp) starting 4 bp from Cbs. This distribution is
independent of the nucleotide sequence in the region or of the orientation
of Cbs. In five of six cases determined, these sites occur at or before a
T, and in the remaining case, the site occurs at or before a G. When
sequences devoid of G or T are placed in this region, telomere addition
still occurs within the region to maintain a similar distance relationship
with Cbs. This efficient and healing process appears to be associated
specifically with Cbs-directed breakage, since it does not occur when DNA
ends are generated by restriction enzyme digestion. These results suggest a
strong mechanistic link between chromosome breakage and telomere formation.
Copyright © 1996, American Society for Microbiology
New telomere formation coupled with site-specific chromosome breakage in Tetrahymena thermophila
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
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