1999 Fiscal Year Final Research Report Summary
Mechanism of senescence in human cells - multistep alterations in genes involved in senescence
| Project/Area Number |
09470406
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional basic dentistry
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| Research Institution | The Nippon Dental University |
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Principal Investigator |
TSUTSUI Takeki The Nippon Dental University, School of Dentistry at Tokyo, Professor, 歯学部, 教授 (00097065)
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| Co-Investigator(Kenkyū-buntansha) |
TAMURA Yukiko The Nippon Dental University, School of Dentistry at Tokyo, Instructor, 歯学部, 助手 (20281438)
HASEGAWA Koko The Nippon Dental University, School of Dentistry at Tokyo, Assistant Professor, 歯学部, 講師 (70053014)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Senescence / Immortalization / Senescence gene / Human cells |
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| Research Abstract |
Five immortal cell lines derived from a Li-Fraumeni syndrome patient (MDAH 087) with a germline mutant p53 allele were characterized with respect to telomere length and genomic instability. The remaining wild type p53 allele is lost in the cell lines. Telomerase activity was undetectable in all immortal cell lines. Five subclones of each cell line and five re-subclones of each of the subclones also showed undetectable telomerase activity. The genes encoding the protein component (hTEP1) and the RNA component (hTERC) of telomerase were expressed in all the immortal cell lines, but the gene for telomerase reverse transcriptase (hTERT) was not. All five immortal cell lines exhibited variability in the mean length of terminal restriction fragments (TRFs). Five subclones of each cell line, and re-subclones of the subclones also showed TRF variability. Chromosome aberrations were observed at high frequencies in these cell lines including the subclones and re-subclones, and the principal type
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s of aberrations were breaks, double minute chromosomes and dicentric chromosomes. Estimated population doublings of the subclones or re-subclones after subcloning or re-subcloning were 22 to 24 population doublings when they were analyzed for TRF length and chromosome aberrations. The results indicate that TRF length variability and chromosome instability are intrinsic characteristics of the telomerasenegative immortal cell lines and occur in a short period. In addition, minisatellite alterations detected by DNA fingerprints were observed in all the immortal cell lines. However, all of the cell lines were negative for microsatellite instability. Tumor-derived human cell lines, HT1080 cells and Hela cells lacking p53 function, exhibited little genomic instability involving chromosomal and minisatellite instabilities. This indicates that the intrinsic features observed in the immortal cell lines lacking telomerase activity could not refult from loss of p53 function. The immortal cell lines may be useful for studying the mechanism associated between telomere maintenance in telomerase-negative cells and genomic instability, particularly involvinge gene amplification and/or recombination. Less
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