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Subcellular localization of histone messenger RNAs on cytoskeleton-associated free polysomes in HeLa S3 cells
Abstract:
We have examined the subcellular distribution of histone mRNA-containing polysomes in HeLa S3 cells to assess the possible relationship between localization of histone mRNAs and the regulation of cellular histone mRNA levels. The distribution of histone mRNAs on free and membrane bound polysomes was examined as well as the association of histone mRNA-containing polysomes with the cytoskeleton. The subcellular localization of histone mRNAs was compared with that of HLA-B7 mRNAs which encode a cell surface antigen. Histone mRNAs were localized predominantly on the free polysomes, whereas the HLA-B7 mRNA was found almost exclusively on membrane bound polysomes. However, both species of mRNA were found associated with the cytoskeleton. Interruption of DNA synthesis by hydroxyurea treatment resulted in a rapid and selective destabilization of histone mRNAs in each subcellular fraction; in contrast, the stability of HLA-B7 mRNA appeared unaffected. The results presented confirm that histone mRNAs are predominantly located on non-membrane bound polysomes and suggest that these polysomes are associated with the cytoskeletal framework.
Insights
Histone messenger RNAs (mRNAs) are primarily found on free polysomes, not membrane-bound ones. Their stability is reduced when DNA synthesis is interrupted, unlike HLA-B7 mRNA.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Cellular regulation of gene expression involves precise control over mRNA localization and stability.
- Histone mRNAs play a critical role in DNA replication and cell division.
- Understanding mRNA localization provides insights into post-transcriptional gene regulation.
Purpose of the Study:
- To investigate the subcellular distribution of histone mRNA-containing polysomes in HeLa S3 cells.
- To determine the relationship between histone mRNA localization and the regulation of cellular histone mRNA levels.
- To compare the localization and stability of histone mRNAs with HLA-B7 mRNAs.
Main Methods:
- Subcellular fractionation to isolate free and membrane-bound polysomes.
- Analysis of mRNA distribution using hybridization techniques.
- Treatment with hydroxyurea to interrupt DNA synthesis and assess mRNA stability.
- Examination of polysome association with the cytoskeleton.
Main Results:
- Histone mRNAs were predominantly localized on free polysomes.
- HLA-B7 mRNA, encoding a cell surface antigen, was found almost exclusively on membrane-bound polysomes.
- Both histone and HLA-B7 mRNAs showed association with the cytoskeleton.
- Hydroxyurea treatment led to rapid, selective destabilization of histone mRNAs in all fractions.
- HLA-B7 mRNA stability remained unaffected by hydroxyurea treatment.
Conclusions:
- Histone mRNAs are predominantly located on non-membrane bound polysomes.
- These polysomes are likely associated with the cytoskeletal framework.
- Histone mRNA stability is sensitive to interruptions in DNA synthesis, suggesting a regulatory mechanism linked to DNA replication.