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Involvement of PIM-1 in DNA fragmentation in mouse NS-1-derived cells
C Takahashi1, Y Harada, H Ariga
1Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Abstract:
In several cell lines derived from mouse NS-1 myeloma cells, internucleosomal fragmentation of chromosomal DNA, a hallmark of apoptosis, was continuously observed. Approximately 15-20% of the cells died when isolated in a 96-well plate, and the surviving cells contained fragmented DNA ('ladder'). Among a variety of genes so far reported to be related to apoptosis, only Pim-1 was expressed at an elevated level in the NS-1 hybridomas as compared in a control myeloma cell line without 'ladder'. Transfection of a Pim-1 expression vector to a 'ladder'-non-producing myeloma line yielded similar internucleosomal DNA fragmentation. The results hence suggested that Pim-1 activates endonucleases responsible for DNA fragmentation during apoptosis and/or repress DNA repair systems to restore fragmented DNA.
Insights
Pim-1 gene expression is linked to DNA fragmentation during apoptosis in mouse myeloma cells. Elevated Pim-1 levels activate endonucleases or inhibit DNA repair, contributing to programmed cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Apoptosis, or programmed cell death, is characterized by internucleosomal DNA fragmentation.
- Mouse NS-1 myeloma cell lines exhibit continuous DNA fragmentation and cell death.
- The specific molecular mechanisms driving DNA fragmentation in these cells require further elucidation.
Purpose of the Study:
- To investigate the role of gene expression in DNA fragmentation observed in NS-1 myeloma cells.
- To identify specific genes associated with the apoptotic DNA fragmentation process.
- To explore the functional impact of identified genes on DNA fragmentation and cell death.
Main Methods:
- Analysis of DNA fragmentation patterns (DNA laddering) in cultured myeloma cell lines.
- Gene expression profiling to compare NS-1 hybridomas with control myeloma cells.
- Gene transfection experiments to assess the functional role of candidate genes.
Main Results:
- Elevated expression of the Pim-1 gene was consistently observed in NS-1 hybridomas exhibiting DNA fragmentation.
- Transfection of a Pim-1 expression vector into a non-fragmenting myeloma cell line induced internucleosomal DNA fragmentation.
- A significant correlation was found between Pim-1 expression levels and the presence of DNA fragmentation.
Conclusions:
- Pim-1 expression is strongly associated with internucleosomal DNA fragmentation, a key event in apoptosis.
- Pim-1 may activate endonucleases that cause DNA fragmentation during apoptosis.
- Alternatively, Pim-1 might suppress DNA repair mechanisms, leading to the accumulation of fragmented DNA.