The role of telomerase and ATM kinases in telomere elongation and in chromosome end-protection [microform]
- Bib ID:
- 3284452
- Format:
- Book and Microform
- Author:
- Chan, Simon Robert Wye Len
- Description:
- 134 p.
- ISBN:
- 0493954422
- Summary:
-
Telomeres have two roles; protecting chromosome ends, and facilitating their complete replication. Telomerase fulfils the latter role by synthesizing new telomeric DNA using its intrinsic RNA component as a template for reverse transcription. Surprisingly, the DNA damage-sensing ATM family kinases Tel1p and Mec1p are required for telomere elongation in S. cerevisiae (Tel1p and Mec1p are homologous to human ATM and ATR respectively). I tested whether the ATM kinases are required for telomerase enzyme activity, or whether it is their action on the telomere that allows telomeric DNA synthesis. I showed that tel1 mec1 cells senesce more slowly than tel1 mec1 tlc1 cells that also lack telomerase RNA, indicating that telomerase may retain limited ability to elongate telomeres in cells without Tel1p and Mec1p.
The catalytic activity of telomerase was normal in extracts from tel1 mec1 cells. Furthermore, two alterations in telomere structure allowed telomere elongation in the absence of Tel1p and Mec1p; deleting the telomere-associated proteins Rif1p and Rif2p, or changing the sequence of telomeric DNA using a novel telomerase RNA template mutation, tlc1-476A. I propose that Tel1p and Mec1p modulate telomere structure to allow the synthesis of new telomeric DNA by a constitutively active telomerase. Telomeres are protected from DNA repair processes and should never fuse to a double-stranded break (DSB). I developed a direct PCR assay for detecting fusions between a telomere and an inducible chromosome break created with the endonuclease HO. Telomeres fused to a DSB in cells that lacked telomerase and Tel1p, and were synergistically increased in tel1 tlc1. Fusion was enriched in G1 phase of the cell cycle.
Chromosome end-protection by telomerase required its catalytic activity, and fusions occurred in tel1 mec1 cells where telomerase cannot elongate telomeres. Cloned telomere-DSB fusions contained very little telomerec DNA, suggesting that rare catastrophic telomere shortening preceded fusion. Importantly, catastrophic telomere shortening and telomere-DSB fusion still occurred in tel1 tlc1 cells in which telomeres had been artificially elongated by transient expression of a Cdc13-Est1p fusion protein. These results show that telomerase, Tel1p and Mec1p have a novel function in telomere end-protection in addition to their roles in telomere elongation.
- Notes:
-
- (UnM)AAI3075292
- Source: Dissertation Abstracts International, Volume: 63-12, Section: B, page: 5650.
- Adviser: Elizabeth H. Blackburn.
- Thesis (Ph.D.)--University of California, San Francisco, 2002.
- Reproduction:
- Microfiche. Ann Arbor, Mich.: University Microfilms International.
- Subject:
- Other authors/contributors:
- University of California, San Francisco
- Copyright:
-
In Copyright
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Copyright status was determined using the following information:
- Material type:
- Literary Dramatic Musical
- Published status:
- Unpublished
- Creation date:
- 2002
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