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Heat shock-induced redistribution of a 160-kDa nuclear matrix protein
A de Graaf1, A M Meijne, A J van Renswoude
1Department of Molecular Cell Biology, University of Utrecht, The Netherlands.
Abstract:
In this paper we describe a 160-kDa protein (p160) which is present in the nuclear matrix of rat, mouse, and human cells. Biochemical and ultrastructural analysis shows that p160 is associated with the internal matrix and is not present in the lamina-pore complex. Immunoelectron microscopy shows that the protein is part of the extranucleolar, fibrogranular network of the nuclear matrix. During an in vivo 42 degrees C heat treatment of HeLa cells, A431 human epidermoid cells, and T24 human bladder carcinoma cells, p160 transiently formed large clusters inside the nucleus. These p160 clusters are associated with the nuclear matrix network, as judged by immunolabeling on isolated nuclear matrices. The percentage of cells showing p160 clusters increased proportionally with longer heat treatments, reaching a maximum after a period of 3 h. At this time 70 +/- 5% of the cells displayed these clusters. Clustering decreased after longer heat treatments and the anti-p160 staining pattern became diffuse granular again. Other nuclear components, such as the A1 antigen of hnRNP (ribonucleoprotein), the Sm antigen of snRNPs, and lamins A and C, did not cluster during the 42 degrees C treatment, indicating that this reallocation is characteristic for the p160 matrix protein. These results demonstrate that p160 is an internal nuclear matrix element with a dynamic spatial distribution.
Insights
A 160-kDa nuclear matrix protein (p160) dynamically clusters within the nucleus during heat stress. This heat-induced clustering is specific to p160, highlighting its role as an internal nuclear matrix component.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The nuclear matrix is a dynamic structure within the cell nucleus.
- Specific proteins within the nuclear matrix play crucial roles in nuclear organization and function.
- Understanding the localization and behavior of nuclear matrix proteins is key to comprehending nuclear architecture.
Purpose of the Study:
- To characterize a 160-kDa protein (p160) found in the nuclear matrix of various cell types.
- To investigate the dynamic spatial distribution of p160 under cellular stress conditions, specifically heat treatment.
- To determine if p160's response to heat stress is unique compared to other nuclear components.
Main Methods:
- Biochemical and ultrastructural analysis to determine p160 localization within the nuclear matrix.
- Immunoelectron microscopy to visualize p160's association with the nuclear matrix network.
- In vivo heat treatment of human cell lines (HeLa, A431, T24) followed by immunolabeling to observe p160 clustering.
- Comparative analysis of p160 clustering with other nuclear components (hnRNP A1, Sm, lamins A/C).
Main Results:
- p160 is identified as a 160-kDa protein localized to the internal nuclear matrix, not the lamina-pore complex.
- Heat treatment (42°C) induces transient, large nuclear clusters of p160 in a dose-dependent manner.
- Maximum p160 clustering (70% of cells) observed after 3 hours of heat treatment, with a return to diffuse granular pattern upon prolonged exposure.
- Other nuclear proteins like hnRNP A1, Sm, and lamins A/C did not exhibit similar clustering, indicating p160's unique response.
Conclusions:
- p160 is an internal nuclear matrix protein with a dynamic spatial distribution.
- Heat stress triggers a characteristic clustering behavior of p160 within the nuclear matrix.
- The specific reallocation of p160 during heat treatment suggests its involvement in the nuclear matrix's response to cellular stress.