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Down-regulation of Ku autoantigen, DNA-dependent protein kinase, and poly(ADP-ribose) polymerase during cellular
A Salminen1, M Helenius, T Lahtinen
1Department of Neuroscience and Neurology, University of Kuopio, Finland. antero.salminen@uku.fi
Abstract:
During aging and cellular senescence mutations accumulate in genomic and mitochondrial DNA. Ku autoantigens, DNA-dependent protein kinase, and poly (ADP-ribose) polymerase have an essential role in DNA damage recognition. Our purpose was to find out whether cellular senescence of fibroblasts affects the protein components that recognize DNA damage and induce the repair process. We compared presenescent and replicatively senescent human WI-38 fibroblasts with each other and with SV-40 immortalized and serum-deficient quiescent WI-38 cells. Our results showed that replicative senescence significantly decreased the nuclear level of both p70 and p86 components of Ku autoantigen. SV-40 immortalization and cellular quiescence did not affect the level of the p86 component but slightly increased that of p70. Both replicative senescence and cellular quiescence decreased the activity of DNA-dependent protein kinase in WI-38 fibroblasts. On the other hand, SV-40 immortalization increased the activity of DNA-dependent protein kinase. The protein level of poly(ADP-ribose) polymerase (PARP) was strongly decreased in replicatively senescent fibroblasts. Quiescence of early-passage fibroblasts also slightly reduced the protein level of PARP. Apoptosis was not observed in replicatively senescent fibroblasts. Our results show that replicative senescence and to some extent cellular quiescence down-regulate the recognition system of DNA damage involving Ku autoantigens, DNA-dependent protein kinase, and PARP and hence could enhance the accumulation of DNA damage during aging.
Insights
Cellular senescence and quiescence down-regulate DNA damage recognition proteins, including Ku autoantigens, DNA-dependent protein kinase, and poly (ADP-ribose) polymerase, potentially increasing DNA damage accumulation during aging.
Area of Science:
- Cellular and Molecular Biology
- Aging Research
- DNA Repair Mechanisms
Background:
- Accumulation of DNA mutations is a hallmark of aging and cellular senescence.
- Ku autoantigens, DNA-dependent protein kinase (DNA-PK), and poly (ADP-ribose) polymerase (PARP) are crucial for recognizing DNA damage.
- Understanding how senescence affects these DNA repair components is vital for aging research.
Purpose of the Study:
- To investigate the impact of replicative senescence and cellular quiescence on key DNA damage recognition proteins in human fibroblasts.
- To compare protein levels and enzyme activities in senescent, quiescent, and immortalized cells.
Main Methods:
- Comparison of presenescent, replicatively senescent, SV-40 immortalized, and serum-deficient quiescent human WI-38 fibroblasts.
- Quantification of nuclear Ku autoantigen components (p70, p86) using Western blotting.
- Assay of DNA-dependent protein kinase activity.
- Measurement of poly (ADP-ribose) polymerase (PARP) protein levels.
Main Results:
- Replicative senescence significantly decreased nuclear p70 and p86 Ku autoantigen levels.
- SV-40 immortalization and quiescence did not alter p86 levels but slightly increased p70.
- Both replicative senescence and quiescence reduced DNA-PK activity, while SV-40 immortalization increased it.
- Replicative senescence and quiescence strongly decreased PARP protein levels.
- No apoptosis was observed in replicatively senescent cells.
Conclusions:
- Replicative senescence and, to some extent, cellular quiescence down-regulate the DNA damage recognition system involving Ku autoantigens, DNA-PK, and PARP.
- This down-regulation may contribute to enhanced DNA damage accumulation during the aging process.
- These findings highlight potential mechanisms linking senescence to age-related genomic instability.