scholarly journals Terminal osteoblast differentiation, mediated by runx2 and p27KIP1, is disrupted in osteosarcoma

2004 ◽  
Vol 167 (5) ◽  
pp. 925-934 ◽  
Author(s):  
David M. Thomas ◽  
Sandra A. Johnson ◽  
Natalie A. Sims ◽  
Melanie K. Trivett ◽  
John L. Slavin ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Osteoblast Differentiation ◽  
Ectopic Expression ◽  
Osteosarcoma Cell ◽  
Cell Cycle Exit ◽  
Retinoblastoma Tumor Suppressor ◽  
Cycle Arrest ◽  
Permanent Cell ◽  
Retinoblastoma Tumor

The molecular basis for the inverse relationship between differentiation and tumorigenesis is unknown. The function of runx2, a master regulator of osteoblast differentiation belonging to the runt family of tumor suppressor genes, is consistently disrupted in osteosarcoma cell lines. Ectopic expression of runx2 induces p27KIP1, thereby inhibiting the activity of S-phase cyclin complexes and leading to the dephosphorylation of the retinoblastoma tumor suppressor protein (pRb) and a G1 cell cycle arrest. Runx2 physically interacts with the hypophosphorylated form of pRb, a known coactivator of runx2, thereby completing a feed-forward loop in which progressive cell cycle exit promotes increased expression of the osteoblast phenotype. Loss of p27KIP1 perturbs transient and terminal cell cycle exit in osteoblasts. Consistent with the incompatibility of malignant transformation and permanent cell cycle exit, loss of p27KIP1 expression correlates with dedifferentiation in high-grade human osteosarcomas. Physiologic coupling of osteoblast differentiation to cell cycle withdrawal is mediated through runx2 and p27KIP1, and these processes are disrupted in osteosarcoma.

scholarly journals Retinoblastoma tumor suppressor protein–dependent methylation of histone H3 lysine 27 is associated with irreversible cell cycle exit

2007 ◽  
Vol 179 (7) ◽  
pp. 1399-1412 ◽  
Author(s):  
Alexandre Blais ◽  
Chris J.C. van Oevelen ◽  
Raphaël Margueron ◽  
Diego Acosta-Alvear ◽  
Brian David Dynlacht
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Histone H3 ◽  
Tumor Suppressor Protein ◽  
Dependent Manner ◽  
Cell Cycle Exit ◽  
Retinoblastoma Tumor Suppressor Protein ◽  
Retinoblastoma Tumor Suppressor ◽  
Permanent Cell ◽  
Retinoblastoma Tumor

The retinoblastoma tumor suppressor protein (pRb) is involved in mitotic exit, promoting the arrest of myoblasts, and myogenic differentiation. However, it is unclear how permanent cell cycle exit is maintained in differentiated muscle. Using RNA interference, expression profiling, and chromatin immunoprecipitations, we show that pRb is essential for cell cycle exit and the differentiation of myoblasts and is also uniquely required to maintain this arrest in myotubes. Remarkably, we also uncover a function for the pRb-related proteins p107 and p130 as enforcers of a G2/M phase checkpoint that prevents progression into mitosis in cells that have lost pRb. We further demonstrate that pRb effects permanent cell cycle exit in part by maintaining trimethylation of histone H3 lysine 27 (H3K27) on cell cycle genes. H3K27 trimethylation silences other genes, including Cyclin D1, in a pRb-independent but polycomb-dependent manner. Thus, our data distinguish two distinct chromatin-based regulatory mechanisms that lead to terminal differentiation.

scholarly journals Cyclin A Is a Functional Target of Retinoblastoma Tumor Suppressor Protein-mediated Cell Cycle Arrest

1999 ◽  
Vol 274 (39) ◽  
pp. 27632-27641 ◽  
Author(s):  
Karen E. Knudsen ◽  
Anne F. Fribourg ◽  
Matthew W. Strobeck ◽  
Jean-Marie Blanchard ◽  
Erik S. Knudsen
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Cyclin A ◽  
Tumor Suppressor Protein ◽  
Retinoblastoma Tumor Suppressor Protein ◽  
Retinoblastoma Tumor Suppressor ◽  
Cycle Arrest ◽  
Retinoblastoma Tumor

scholarly journals Inactivation of both the Retinoblastoma Tumor Suppressor and p21 by the Human Papillomavirus Type 16 E7 Oncoprotein Is Necessary To Inhibit Cell Cycle Arrest in Human Epithelial Cells

2002 ◽  
Vol 76 (20) ◽  
pp. 10559-10568 ◽  
Author(s):  
Anna-Marija Helt ◽  
Jens Oliver Funk ◽  
Denise A. Galloway
Keyword(s):  
Cell Cycle ◽  
Human Papillomavirus ◽  
Tumor Suppressor ◽  
Epithelial Cells ◽  
Cell Cycle Arrest ◽  
Cell Cycle Control ◽  
E7 Oncoprotein ◽  
Retinoblastoma Tumor Suppressor ◽  
Cycle Arrest ◽  
Retinoblastoma Tumor

ABSTRACT The human papillomavirus (HPV) type 16 E7 oncoprotein must inactivate the retinoblastoma tumor suppressor (Rb) pathway to bypass G1 arrest. However, E7 C-terminal mutants that were able to inactivate Rb were unable to bypass DNA damage-induced G1 arrest and keratinocyte senescence, suggesting that the E7 C terminus may target additional G1 regulators. The E7 C-terminal mutant proteins E7 CVQ68-70AAA and E7 Δ79-83 (deletion of positions 79 through 83) were further tested in several models of cell cycle arrest associated with elevated levels of p21. C-terminal mutations rendered E7 unable to induce S phase and endoreduplication in differentiated keratinocytes and rendered it less efficient in delaying senescence of human mammary epithelial cells. Interestingly, when cell cycle arrest was induced with a peptide form of p21, the E7 C-terminal mutants were deficient in overcoming arrest, whereas a mutant defective in Rb binding was competent in inhibiting G1 arrest. These results suggest that the inactivation of both p21 and Rb by E7 contributes to subversion of cell cycle control in normal human epithelia but that neither p21 nor Rb inactivation alone is sufficient.

scholarly journals RBP1 Recruits the mSIN3-Histone Deacetylase Complex to the Pocket of Retinoblastoma Tumor Suppressor Family Proteins Found in Limited Discrete Regions of the Nucleus at Growth Arrest

2001 ◽  
Vol 21 (8) ◽  
pp. 2918-2932 ◽  
Author(s):  
Albert Lai ◽  
Brian K. Kennedy ◽  
David A. Barbie ◽  
Nicholas R. Bertos ◽  
Xiang Jiao Yang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Histone Deacetylase ◽  
Family Members ◽  
Growth Stimulation ◽  
Stable Complex ◽  
Induce Cell Cycle Arrest ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor ◽  
Class I Hdacs

ABSTRACT Retinoblastoma (RB) tumor suppressor family pocket proteins induce cell cycle arrest by repressing transcription of E2F-regulated genes through both histone deacetylase (HDAC)-dependent and -independent mechanisms. In this study we have identified a stable complex that accounts for the recruitment of both repression activities to the pocket. One component of this complex is RBP1, a known pocket-binding protein that exhibits both HDAC-dependent and -independent repression functions. RB family proteins were shown to associate via the pocket with previously identified mSIN3-SAP30-HDAC complexes containing exclusively class I HDACs. Such enzymes do not interact directly with RB family proteins but rather utilize RBP1 to target the pocket. This mechanism was shown to account for the majority of RB-associated HDAC activity. We also show that in quiescent normal human cells this entire RBP1-mSIN3-SAP30-HDAC complex colocalizes with both RB family members and E2F4 in a limited number of discrete regions of the nucleus that in other studies have been shown to represent the initial origins of DNA replication following growth stimulation. These results suggest that RB family members, at least in part, drive exit from the cell cycle by recruitment of this HDAC complex via RBP1 to repress transcription from E2F-dependent promoters and possibly to alter chromatin structure at DNA origins.

scholarly journals Regulation of the Chlamydomonas Cell Cycle by a Stable, Chromatin-Associated Retinoblastoma Tumor Suppressor Complex

2010 ◽  
Vol 22 (10) ◽  
pp. 3331-3347 ◽  
Author(s):  
Bradley J.S.C. Olson ◽  
Michael Oberholzer ◽  
Yubing Li ◽  
James M. Zones ◽  
Harjivan S. Kohli ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor

scholarly journals Retinoblastoma Tumor Suppressor: Analyses of Dynamic Behavior in Living Cells Reveal Multiple Modes of Regulation

2003 ◽  
Vol 23 (22) ◽  
pp. 8172-8188 ◽  
Author(s):  
Steven P. Angus ◽  
David A. Solomon ◽  
Lioba Kuschel ◽  
Robert F. Hennigan ◽  
Erik S. Knudsen
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Dynamic Behavior ◽  
Transcriptional Repression ◽  
Fluorescent Protein ◽  
Dynamic Equilibrium ◽  
Living Cells ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor

ABSTRACT The retinoblastoma tumor suppressor, RB, assembles multiprotein complexes to mediate cell cycle inhibition. Although many RB binding partners have been suggested to underlie these functions, the validity of these interactions on the behavior of RB complexes in living cells has not been investigated. Here, we studied the dynamic behavior of RB by using green fluorescent protein-RB fusion proteins. Although these proteins were universally nuclear, phosphorylation or oncoprotein binding mediated their active exclusion from the nucleolus. In vivo imaging approaches revealed that RB exists in dynamic equilibrium between a highly mobile and a slower diffusing species, and genetic lesions associated with tumorigenesis increased the fraction of RB in a highly mobile state. The RB complexes dictating cell cycle arrest were surprisingly dynamic and harbored a relatively short residence time on chromatin. In contrast, this rapid exchange was attenuated in cells that are hypersensitive to RB, suggesting that responsiveness may inversely correlate with mobility. The stability of RB dynamics within the cell was additionally modified by the presence and function of critical corepressors. Last, the RB-assembled complexes present in living cells were primarily associated with E2F binding sites in chromatin. In contrast to RB, E2F1 consistently maintained a stable association with E2F sites regardless of cell type. Together, these results elucidate the kinetic framework of RB tumor suppressor action in transcriptional repression and cell cycle regulation.

A Critical Role for the Retinoblastoma Tumor Suppressor Gene in Hematopoietic Stem Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2548-2548
Author(s):  
Hartmut Geiger ◽  
Marie-Dominique Filippi ◽  
Theodosia A. Kalfa ◽  
Deidre Daria
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Function ◽  
Fetal Liver ◽  
Critical Role ◽  
Lymphoid Cells ◽  
Hematopoietic Stem ◽  
Retinoblastoma Tumor Suppressor ◽  
Retinoblastoma Tumor

Abstract The retinoblastoma tumor suppressor protein (RB) plays important roles in the control of the cell cycle, DNA-damage checkpoint, differentiation and apoptosis. It is estimated that RB is dysfunctional/inactivated in up to 40% of human leukemias. Positive as well as inhibitory signals are integrated into the phosphorylation of the RB protein to regulate the G1 to S-phase progression of the cell cycle. Despite the importance of RB in leukemia, the consequences of loss of RB on hematopoietic stem and progenitor cell (HSPC) function in vivo are still not clear and have been controversially discussed. Using Cre-enzyme expression driven by the hematopoietic specific Vav1-promotor, we generated mice that are constitutively deficient in RB (hemRb−/− animals) in HSPCs. HemRb−/− mice showed anemia with an increased number of reticulocytes in PB, consistent with a published role of RB in erythroid differentiation. In addition, the frequency of Mac-1 positive cells in BM was increased to 67% compared to 47% in control animals, whereas the frequency of B220 positive B-lymphoid cells was almost 10-fold reduced, without affecting the T-lymphoid compartment. HemRb−/− mice possessed a 3-fold enlarged spleen with a 5-fold increased number of colony-forming cells (CFCs) and severe extramedullary hematopoiesis, a phenotype also reported for animals transplanted with Rb−/− fetal liver cells. BM of hemRb−/− mice showed an almost 3-fold reduction of HSC frequency, measured by the cobblestone-area forming cell assay (CAFC) assay, but not a decrease in the number of HSCs determined by cell surface staining and flow cytometry. Upon transplantation into NOD/SCID animals or upon competitive transplantation into C57BL/6. CD45.1 animals, HSPCs from hemRb−/− mice contributed 4 to 6-fold less to hematopoiesis. HSPCs from hemRb−/− animals were neither impaired in their ability to home to the BM, nor did they show increased apoptosis. Finally, we detected a significant 4-fold decrease in stem cell function/numbers upon stress caused by 5-FU treatment in hemRB−/− mice compared to control animals. We conclude that upon transplantation/stress, HSPCs from hemRb−/− animals are impaired in their self-renewal function. HemRb−/− animals also showed a 2-fold increase in the frequency of CFCs in peripheral blood. As we detected no increased leukemia incidence in the hemRb−/− animals (now up to 1 year of age), loss of the tumor suppressor RB in hematopoietic cells might be regarded as necessary, but not sufficient for causing early onset leukemia. In summary, loss of RB results in context/localization dependent phenotypes in the hematopoietic hierarchy, influencing stem and progenitor cells in function, localization and differentiation ability.

Relationship between the loss of the retinoblastoma tumor suppressor and radiosensitivity.

2011 ◽  
Vol 29 (7_suppl) ◽  
pp. 34-34 ◽  
Author(s):  
R. B. Den ◽  
S. Ciment ◽  
A. Sharma ◽  
H. Mellert ◽  
S. Mc-Mahon ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Cell Cycle ◽  
Dna Damage ◽  
Tumor Suppressor ◽  
Ionizing Radiation ◽  
Cell Survival ◽  
Retinoblastoma Tumor Suppressor ◽  
Clonogenic Cell ◽  
Retinoblastoma Tumor

34 Background: Prostate cancer is the most frequently diagnosed malignancy and the second leading cause of cancer death in U.S. men. The retinoblastoma tumor suppressor protein, RB, plays a critical role in cell cycle regulation. Loss of RB has been observed in 25–30% of prostate cancers and is correlated with increasing tumor stage and grade. The clinical consequences of RB loss are unknown. We have previously shown that RB loss results in a castrate resistant phenotype. We hypothesized that RB loss would downregulate the G1-S cell cycle arrest normally induced by irradiation, inhibit DNA repair, and subsequently sensitize cells to mitotic catastrophe. Methods: Experimental work was performed with multiple isogenic prostate cancer cell lines (hormone sensitive: LNCaP and LAP-C4 cells and hormone resistant C42 cells; stable knockdown of RB using shRNA). Gamma H2AX assays were used to quantitate DNA damage and PARP cleavage and Caspase 3 were used to quantitate apoptosis. FACS analysis with BrdU was used to assess the cell cycle. Cell survival was measured using the clonogenic cell survival assay. In vivo work was performed in nude mice with tumor xenografts. Results: We observed that loss of RB increased radioresponsiveness in both transient and clonogenic cell survival assays in all cell lines (p<0.05). Cell death was not mediated through increased apoptosis, however, there was increased cell cycling despite the presence of DNA damage in the RB knockdown cells. In vivo xenografts of the RB deficient tumors exhibited diminished tumor mass, lower PSA kinetics and decreased tumor growth after treatment with single fraction of ionizing radiation in comparison to RB intact tumors (p<0.05). Conclusions: Loss of RB results in a differential response to ionizing radiation. Isogenic cells with RB knockdown are more sensitive to DNA damage and result in reduced cell survival. RB status is integral to determining which therapeutic modality should be employed in the management of prostate cancer. No significant financial relationships to disclose.

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