## Abstract Protein kinase CK2 is a ubiquitous protein serine/threonine kinase that is involved in cell growth and proliferation as well as suppression of apoptosis. Several studies have suggested that the kinase plays a role in cell cycle progression; however, changes in enzyme activity during pha
Cell cycle-dependent nuclear location of the matricellular protein SPARC: Association with the nuclear matrix
β Scribed by M.D. Gooden; R.B. Vernon; J.A. Bassuk; E.H. Sage
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 594 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0730-2312
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β¦ Synopsis
Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that inhibits cellular adhesion and proliferation. In this study, we report the detection of SPARC in the interphase nuclei of embryonic chicken cells in vivo. Differential partitioning of SPARC was also noted in the cytoplasm of these cells during discrete stages of M-phase: cells in metaphase and anaphase exhibited strong cytoplasmic immunoreactivity, whereas cells in telophase were devoid of labeling. Immunocytochemical analysis of embryonic chicken cells in vitro likewise showed the presence of SPARC in the nucleus. Furthermore, elution of soluble proteins and DNA from these cells indicated that SPARC might be a component of the nuclear matrix. We subsequently examined cultured bovine aortic endothelial cells, which initially appeared to express SPARC only in the cytoplasm. However, after elution of soluble proteins and chromatin, we also detected SPARC in the nuclear matrix of these cells. Embryonic chicken cells incubated with recombinant SPARC were seen to take up the protein and to translocate it to the nucleus progressively over a period of 17 h. These observations provide new information about SPARC, generally recognized as a secreted glycoprotein that mediates interactions between cells and components of the extracellular matrix. The evidence presented in this study indicates that SPARC might subserve analogous functions in the nuclear matrix.
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