Limits...
The human polycomb group complex associates with pericentromeric heterochromatin to form a novel nuclear domain.

Saurin AJ, Shiels C, Williamson J, Satijn DP, Otte AP, Sheer D, Freemont PS - J. Cell Biol. (1998)

Bottom Line: The Polycomb group (PcG) complex is a chromatin-associated multiprotein complex, involved in the stable repression of homeotic gene activity in Drosophila.Furthermore, these heterochromatin-bound PcG complexes remain stably associated throughout mitosis, thereby allowing the potential inheritance of the PcG complex through successive cell divisions.We discuss these results in terms of the known function of the PcG complex as a transcriptional repression complex.

View Article: PubMed Central - PubMed

Affiliation: Molecular Structure and Function Laboratory, Imperial Cancer Research Fund, London WC2A 3PX, United Kingdom.

ABSTRACT
The Polycomb group (PcG) complex is a chromatin-associated multiprotein complex, involved in the stable repression of homeotic gene activity in Drosophila. Recently, a mammalian PcG complex has been identified with several PcG proteins implicated in the regulation of Hox gene expression. Although the mammalian PcG complex appears analogous to the complex in Drosophila, the molecular mechanisms and functions for the mammalian PcG complex remain unknown. Here we describe a detailed characterization of the human PcG complex in terms of cellular localization and chromosomal association. By using antibodies that specifically recognize three human PcG proteins- RING1, BMI1, and hPc2-we demonstrate in a number of human cell lines that the PcG complex forms a unique discrete nuclear structure that we term PcG bodies. PcG bodies are prominent novel nuclear structures with the larger PcG foci generally localized near the centromeres, as visualized with a kinetochore antibody marker. In both normal fetal and adult fibroblasts, PcG bodies are not randomly dispersed, but appear clustered into defined areas within the nucleus. We show in three different human cell lines that the PcG complex can tightly associate with large pericentromeric heterochromatin regions (1q12) on chromosome 1, and with related pericentromeric sequences on different chromosomes, providing evidence for a mammalian PcG-heterochromatin association. Furthermore, these heterochromatin-bound PcG complexes remain stably associated throughout mitosis, thereby allowing the potential inheritance of the PcG complex through successive cell divisions. We discuss these results in terms of the known function of the PcG complex as a transcriptional repression complex.

Show MeSH

Related in: MedlinePlus

The human RING1  protein localizes to discrete  nuclear concentrated foci in  a number of human cell lines.  Polyclonal antisera against  the human RING1 protein  was used to immunolocalize  endogenous RING1 in: (a)  2C4 human fibrosarcoma  cells, a derivative of the  HT1080 cell line; (b) U-2 OS  human osteosarcoma cells;  (c) SAOS-2 human osteosarcoma cells; (d) MRC-5 normal human fetal lung fibroblast cells; (e) CS22F normal  human adult fibroblast cells;  and (f) human neonatal foreskin tissue section. Images  represent a projection of multiple optical sections through  the cell. Bar, 10 μm in all  panels.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2132874&req=5

Figure 1: The human RING1 protein localizes to discrete nuclear concentrated foci in a number of human cell lines. Polyclonal antisera against the human RING1 protein was used to immunolocalize endogenous RING1 in: (a) 2C4 human fibrosarcoma cells, a derivative of the HT1080 cell line; (b) U-2 OS human osteosarcoma cells; (c) SAOS-2 human osteosarcoma cells; (d) MRC-5 normal human fetal lung fibroblast cells; (e) CS22F normal human adult fibroblast cells; and (f) human neonatal foreskin tissue section. Images represent a projection of multiple optical sections through the cell. Bar, 10 μm in all panels.

Mentions: To characterize in detail the subcellular localization of human RING1, we raised polyclonal antisera against full-length recombinant RING1 protein, and against two 15-residue synthetic peptides (data not shown). The immunofluorescent signal was the same for all the antisera with the specificity of the antibody for RING1, shown by specifically blocking the antipeptide antisera with the immunizing peptide, resulting in total loss of the immunofluorescent signal (data not shown). There was no loss of immunofluorescent signal when the antisera was blocked using a nonimmunizing RING1 peptide. Antibody specificity was further demonstrated by the recognition of in vitro–translated RING1 and RING1 from whole-cell extracts by immunoblot analyses (data not shown). We then performed double immunofluorescent labeling experiments with RING1 and antibodies against BMI1 and hPc2 (Satijn et al., 1997a; Satijn et al., 1997b) in a variety of transformed and primary human cell lines including 2C4 (HT1080 derivative), U-2 OS, SAOS-2, HEP-2, SW480, T24, HeLa, A431, MRC-5, WI-38, CS22F, and frozen human foreskin tissue sections (Fig. 1 and data not shown).


The human polycomb group complex associates with pericentromeric heterochromatin to form a novel nuclear domain.

Saurin AJ, Shiels C, Williamson J, Satijn DP, Otte AP, Sheer D, Freemont PS - J. Cell Biol. (1998)

The human RING1  protein localizes to discrete  nuclear concentrated foci in  a number of human cell lines.  Polyclonal antisera against  the human RING1 protein  was used to immunolocalize  endogenous RING1 in: (a)  2C4 human fibrosarcoma  cells, a derivative of the  HT1080 cell line; (b) U-2 OS  human osteosarcoma cells;  (c) SAOS-2 human osteosarcoma cells; (d) MRC-5 normal human fetal lung fibroblast cells; (e) CS22F normal  human adult fibroblast cells;  and (f) human neonatal foreskin tissue section. Images  represent a projection of multiple optical sections through  the cell. Bar, 10 μm in all  panels.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132874&req=5

Figure 1: The human RING1 protein localizes to discrete nuclear concentrated foci in a number of human cell lines. Polyclonal antisera against the human RING1 protein was used to immunolocalize endogenous RING1 in: (a) 2C4 human fibrosarcoma cells, a derivative of the HT1080 cell line; (b) U-2 OS human osteosarcoma cells; (c) SAOS-2 human osteosarcoma cells; (d) MRC-5 normal human fetal lung fibroblast cells; (e) CS22F normal human adult fibroblast cells; and (f) human neonatal foreskin tissue section. Images represent a projection of multiple optical sections through the cell. Bar, 10 μm in all panels.
Mentions: To characterize in detail the subcellular localization of human RING1, we raised polyclonal antisera against full-length recombinant RING1 protein, and against two 15-residue synthetic peptides (data not shown). The immunofluorescent signal was the same for all the antisera with the specificity of the antibody for RING1, shown by specifically blocking the antipeptide antisera with the immunizing peptide, resulting in total loss of the immunofluorescent signal (data not shown). There was no loss of immunofluorescent signal when the antisera was blocked using a nonimmunizing RING1 peptide. Antibody specificity was further demonstrated by the recognition of in vitro–translated RING1 and RING1 from whole-cell extracts by immunoblot analyses (data not shown). We then performed double immunofluorescent labeling experiments with RING1 and antibodies against BMI1 and hPc2 (Satijn et al., 1997a; Satijn et al., 1997b) in a variety of transformed and primary human cell lines including 2C4 (HT1080 derivative), U-2 OS, SAOS-2, HEP-2, SW480, T24, HeLa, A431, MRC-5, WI-38, CS22F, and frozen human foreskin tissue sections (Fig. 1 and data not shown).

Bottom Line: The Polycomb group (PcG) complex is a chromatin-associated multiprotein complex, involved in the stable repression of homeotic gene activity in Drosophila.Furthermore, these heterochromatin-bound PcG complexes remain stably associated throughout mitosis, thereby allowing the potential inheritance of the PcG complex through successive cell divisions.We discuss these results in terms of the known function of the PcG complex as a transcriptional repression complex.

View Article: PubMed Central - PubMed

Affiliation: Molecular Structure and Function Laboratory, Imperial Cancer Research Fund, London WC2A 3PX, United Kingdom.

ABSTRACT
The Polycomb group (PcG) complex is a chromatin-associated multiprotein complex, involved in the stable repression of homeotic gene activity in Drosophila. Recently, a mammalian PcG complex has been identified with several PcG proteins implicated in the regulation of Hox gene expression. Although the mammalian PcG complex appears analogous to the complex in Drosophila, the molecular mechanisms and functions for the mammalian PcG complex remain unknown. Here we describe a detailed characterization of the human PcG complex in terms of cellular localization and chromosomal association. By using antibodies that specifically recognize three human PcG proteins- RING1, BMI1, and hPc2-we demonstrate in a number of human cell lines that the PcG complex forms a unique discrete nuclear structure that we term PcG bodies. PcG bodies are prominent novel nuclear structures with the larger PcG foci generally localized near the centromeres, as visualized with a kinetochore antibody marker. In both normal fetal and adult fibroblasts, PcG bodies are not randomly dispersed, but appear clustered into defined areas within the nucleus. We show in three different human cell lines that the PcG complex can tightly associate with large pericentromeric heterochromatin regions (1q12) on chromosome 1, and with related pericentromeric sequences on different chromosomes, providing evidence for a mammalian PcG-heterochromatin association. Furthermore, these heterochromatin-bound PcG complexes remain stably associated throughout mitosis, thereby allowing the potential inheritance of the PcG complex through successive cell divisions. We discuss these results in terms of the known function of the PcG complex as a transcriptional repression complex.

Show MeSH
Related in: MedlinePlus