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Mechanisms of H1o accumulation in mouse neuroblastoma cells differ with different treatments
Abstract:
The accumulation of histone H1o in mouse NIE-115 neuroblastoma cells was measured during the course of three treatments that block cell division. Over the course of 12 days, these treatments, 5 mM butyrate, 2% dimethyl sulfoxide, and serum withdrawal, all resulted in decreased levels of DNA synthesis and increased levels of H1o (in absolute terms and relative to the other H1 histones, H1abc). However, the increase in H1o differed comparing butyrate treatment, where there was a 6-fold increase in the H1o/H1abc ratio, with the other two treatments which both had only 3-fold increases in the H1o/H1abc ratio. The mechanism for increasing H1o differed for each of the three treatments and involved differential changes in both synthesis and degradation of the H1 subfractions to favor H1o accumulation on the chromatin. Despite the obvious correlation of the increase in H1o levels with the inhibition of DNA replication, we also showed that increases in H1o can occur without any change in DNA synthesis when cells are switched from media containing dimethyl sulfoxide to media with butyrate as the blocking agent. Finally, there was no correlation between the production of neurites in this cell line and H1o accumulation, arguing against simple, direct involvement of H1o in differentiation.
Insights
Histone H1o accumulation increases when neuroblastoma cells stop dividing due to butyrate, DMSO, or serum withdrawal. However, the mechanisms and extent of H1o increase vary by treatment, and H1o does not directly drive neurite differentiation.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Histone H1 variants play crucial roles in chromatin structure and gene regulation.
- Histone H1o is specifically associated with cellular differentiation and chromatin condensation.
- Understanding the regulation of H1o accumulation is key to deciphering its function in cellular processes.
Purpose of the Study:
- To investigate the accumulation of histone H1o in NIE-115 neuroblastoma cells under conditions that inhibit cell division.
- To compare the effects of different cell division blocking agents (butyrate, dimethyl sulfoxide, serum withdrawal) on H1o levels.
- To elucidate the mechanisms underlying H1o accumulation and its relationship with DNA synthesis and differentiation.
Main Methods:
- NIE-115 neuroblastoma cells were treated with 5 mM butyrate, 2% dimethyl sulfoxide, or serum withdrawal for 12 days.
- Levels of histone H1o and other H1 subfractions (H1abc) were quantified.
- DNA synthesis rates were measured.
- Changes in histone synthesis and degradation were analyzed.
Main Results:
- All three treatments decreased DNA synthesis and increased H1o levels.
- Butyrate treatment showed a greater increase in the H1o/H1abc ratio (6-fold) compared to dimethyl sulfoxide and serum withdrawal (3-fold).
- Mechanisms of H1o accumulation involved differential regulation of synthesis and degradation, varying with treatment; H1o increase can occur independently of DNA synthesis changes.
Conclusions:
- Histone H1o accumulation is a common response to cell division arrest in neuroblastoma cells, but the specific regulatory mechanisms differ.
- The extent of H1o accumulation varies depending on the agent used to block cell division.
- H1o accumulation is not directly correlated with neurite production, suggesting it is not a primary driver of differentiation in this model.