Cyclin D3 Governs Clonal Expansion of Dark Zone Germinal Center B Cells
29
Citation
53
Reference
10
Related Paper
Citation Trend
Abstract:
Germinal center (GC) B cells surge in their proliferative capacity, which poses a direct risk for B cell malignancies. G1- to S-phase transition is dependent on the expression and stability of D-type cyclins. We show that cyclin D3 expression specifically regulates dark zone (DZ) GC B cell proliferation. B cell receptor (BCR) stimulation of GC B cells downregulates cyclin D3 but induces c-Myc, which subsequently requires cyclin D3 to exert GC expansion. Control of DZ proliferation requires degradation of cyclin D3, which is dependent on phosphorylation of residue Thr283 and can be bypassed by cyclin D3T283A hyperstabilization as observed in B cell lymphoma. Thereby, selected GC B cells in the light zone potentially require disengagement from BCR signaling to accumulate cyclin D3 and undergo clonal expansion in the DZ.Keywords:
Cyclin D3
Cyclin D
Cyclin A2
Cyclin B
Cyclin D2
Cyclin A
Cyclin E
Abstract Cyclin D2 affects B cell proliferation and differentiation in vivo. It is rate-limiting for B cell receptor (BCR)-dependent proliferation of B cells, and cyclin D2−/− mice lack CD5+(B1) B lymphocytes. We show here that the bone marrow (BM) of cyclin D2−/− mice contains half the numbers of Sca1+B220+ B cell progenitors but normal levels of Sca1+ progenitor cells of other lineages. In addition, clonal analysis of BM from the cyclin D2−/− and cyclin D2+/+ mice confirmed that there were fewer B cell progenitors (B220+) in the cyclin D2−/− mice. In addition, the colonies from cyclin D2−/− mice were less mature (CD19lo) than those from cyclin D2+/+ mice (CD19Hi). The number of mature B2 B cells in vivo is the same in cyclin D2−/− and cyclin D2+/+ animals. Lack of cyclin D2 protein may be compensated by cyclin D3, as cyclin-dependent kinase (cdk)6 coimmunoprecipitates with cyclin D3 but not cyclin D1 from BM mononuclear cells of cyclin D2−/− mice. It is active, as endogenous retinoblastoma protein is phosphorylated at the cdk6/4-cyclin D-specific sites, S807/811. We conclude that cyclin D2 is rate-limiting for the production of B lymphoid progenitor cells whose proliferation does not depend on BCR signaling.
Cyclin A2
Cyclin D2
Cyclin D
Cyclin B
Cyclin A
Cyclin E
Cyclin D3
Cite
Citations (28)
Background The normal progression of the cell cycle requires sequential expression of cyclins. Rapid induction of cyclin D1 and its associated binding with cyclin-dependent kinases, in the presence or absence of mitogenic signals, often is considered a rate-limiting step during cell cycle progression through the G1 phase. Methodology/Principal Findings In the present study, human umbilical cord blood stem cells (hUCBSC) in co-cultures with glioblastoma cells (U251 and 5310) not only induced G0-G1 phase arrest, but also reduced the number of cells at S and G2-M phases of cell cycle. Cell cycle regulatory proteins showed decreased expression levels upon treatment with hUCBSC as revealed by Western and FACS analyses. Inhibition of cyclin D1 activity by hUCBSC treatment is sufficient to abolish the expression levels of Cdk 4, Cdk 6, cyclin B1, β-Catenin levels. Our immuno precipitation experiments present evidence that, treatment of glioma cells with hUCBSC leads to the arrest of cell-cycle progression through inactivation of both cyclin D1/Cdk 4 and cyclin D1/Cdk 6 complexes. It is observed that hUCBSC, when co-cultured with glioma cells, caused an increased G0-G1 phase despite the reduction of G0-G1 regulatory proteins cyclin D1 and Cdk 4. We found that this reduction of G0-G1 regulatory proteins, cyclin D1 and Cdk 4 may be in part compensated by the expression of cyclin E1, when co-cultured with hUCBSC. Co-localization experiments under in vivo conditions in nude mice brain xenografts with cyclin D1 and CD81 antibodies demonstrated, decreased expression of cyclin D1 in the presence of hUCBSC. Conclusions/Significance This paper elucidates a model to regulate glioma cell cycle progression in which hUCBSC acts to control cyclin D1 induction and in concert its partner kinases, Cdk 4 and Cdk 6 by mediating cell cycle arrest at G0-G1 phase.
Cyclin A2
Cyclin D
Cyclin A
Cyclin B
Cyclin E
Cyclin D2
Cyclin D3
Cite
Citations (27)
Cyclin D
Cyclin A2
Cyclin E
Cyclin A
Cyclin B
Cyclin-dependent kinase 6
Cyclin D2
Cyclin D3
Cyclin-dependent kinase complex
Cite
Citations (51)
Cyclin D
Cyclin D3
Cyclin B
Cyclin A
Cyclin A2
Cyclin E
Cyclin D2
Cite
Citations (23)
B cyclins regulate G2-M transition. Because human somatic cells continue to cycle after reduction of cyclin B1 (cycB1) or cyclin B2 (cycB2) by RNA interference (RNAi), and because cycB2 knockout mice are viable, the existence of two genes should be an optimization. To explore this idea, we generated HeLa BD™ Tet-Off cell lines with inducible cyclin B1- or B2-EGFP that were RNAi resistant. Cultures were treated with RNAi and/or doxycycline (Dox) and bromodeoxyuridine. We measured G2 and M transit times and 4C cell accumulation. In the absence of ectopic B cyclin expression, knockdown (kd) of either cyclin increased G2 transit. M transit was increased by cycB1 kd but decreased by cycB2 depletion. This novel difference was further supported by time-lapse microscopy. This suggests that cycB2 tunes mitotic timing, and we speculate that this is through regulation of a Golgi checkpoint. In the presence of endogenous cyclins, expression of active B cyclin-EGFPs did not affect G2 or M phase times. As previously shown, B cyclin co-depletion induced G2 arrest. Expression of either B cyclin-EGFP completely rescued knockdown of the respective endogenous cyclin in single kd experiments, and either cyclin-EGFP completely rescued endogenous cyclin co-depletion. Most of the rescue occurred at relatively low levels of exogenous cyclin expression. Therefore, cycB1 and cycB2 are interchangeable for ability to promote G2 and M transition in this experimental setting. Cyclin B1 is thought to be required for the mammalian somatic cell cycle, while cyclin B2 is thought to be dispensable. However, residual levels of cyclin B1 or cyclin B2 in double knockdown experiments are not sufficient to promote successful mitosis, yet residual levels are sufficient to promote mitosis in the presence of the dispensible cyclin B2. We discuss a simple model that would explain most data if cyclin B1 is necessary.
Cyclin A
Cyclin A2
Cyclin B1
Cyclin B
Cyclin D
Cyclin E
Cyclin D3
Cyclin D2
Cite
Citations (62)
Abstract Overexpression of D-type cyclins in human cancer frequently occurs as a result of protein stabilization, emphasizing the importance of identification of the machinery that regulates their ubiqutin-dependent degradation. Cyclin D3 is overexpressed in ~50% of Burkitt’s lymphoma correlating with a mutation of Thr-283. However, the E3 ligase that regulates phosphorylated cyclin D3 and whether a stabilized, phosphorylation deficient mutant of cyclin D3, has oncogenic activity are undefined. We describe the identification of SCF-Fbxl8 as the E3 ligase for Thr-283 phosphorylated cyclin D3. SCF-Fbxl8 poly-ubiquitylates p-Thr-283 cyclin D3 targeting it to the proteasome. Functional investigation demonstrates that Fbxl8 antagonizes cell cycle progression, hematopoietic cell proliferation, and oncogene-induced transformation through degradation of cyclin D3, which is abolished by expression of cyclin D3T283A, a non-phosphorylatable mutant. Clinically, the expression of cyclin D3 is inversely correlated with the expression of Fbxl8 in lymphomas from human patients implicating Fbxl8 functions as a tumor suppressor.
Cyclin D3
Cyclin D
Cyclin A2
Cyclin E
Cyclin A
Cyclin B
Cyclin D2
Cyclin-dependent kinase complex
SKP2
Cite
Citations (18)
Cyclin D2 is the only D-type cyclin expressed in mature mouse B-lymphocytes, and its expression is associated with retinoblastoma protein (pRB) and pRB-related protein phosphorylation and induction of E2F activity, as B-cells enter the cell cycle following stimulation via surface IgM and/or CD40. Cyclin D-dependent kinase activity is required for cell proliferation, yet cyclin D2−/− mice have normal levels of mature B-lymphocytes. Here we show that B-lymphocytes from cyclin D2−/− mice can proliferate in response to anti-IgM and anti-CD40, but the time taken to enter S-phase is longer than for the corresponding cyclin D2+/+ cells. This is due to the compensatory induction of cyclin D3, but not cyclin D1, which causes pRb phosphorylation on CDK4-specific sites. This is the first demonstration that loss of a D-type cyclin causes specific expression and functional compensation by another member of the family in vivo and provides a rationale for the presence of mature B-lymphocytes in cyclin D2−/− mice.
Cyclin D
Cyclin A2
Cyclin D3
Cyclin B
Cyclin D2
Cyclin A
Cyclin E
Cyclin-dependent kinase complex
Retinoblastoma protein
Cyclin-dependent kinase 4
Cite
Citations (121)
Abstract Peritoneal B-1a cells differ from splenic B-2 cells in the molecular mechanisms that control G0-S progression. In contrast to B-2 cells, cyclin D2 is up-regulated in a rapid and transient manner in phorbol ester (PMA)-stimulated B-1a cells, whereas cyclin D3 does not accumulate until late G1 phase. This nonoverlapping expression of cyclins D2 and D3 suggests distinct functions for these proteins in B-1a cells. To investigate the contribution of cyclin D3 in the proliferation of B-1a cells, we transduced p16INK4a peptidyl mimetics (TAT-p16) into B-1a cells before cyclin D3 induction to specifically block cyclin D3-cyclin-dependent kinase 4/6 assembly. TAT-p16 inhibited DNA synthesis in B-1a cells stimulated by PMA, CD40L, or LPS as well as endogenous pRb phosphorylation by cyclin D-cyclin-dependent kinase 4/6. Unexpectedly, however, cyclin D3-deficient B-1a cells proliferated in a manner similar to wild-type B-1a cells following PMA or LPS stimulation. This was due, at least in part, to the compensatory sustained accumulation of cyclin D2 throughout G0-S progression. Taken together, experiments in which cyclin D3 was inhibited in real time demonstrate the key role this cyclin plays in normal B-1a cell mitogenesis, whereas experiments with cyclin D3-deficient B-1a cells show that cyclin D2 can compensate for cyclin D3 loss in mutant mice.
Cyclin D
Cyclin D3
Cyclin A2
Cyclin A
Cyclin B
Cyclin E
Cyclin D2
Cyclin-dependent kinase complex
Cite
Citations (15)
Megakaryocytes are platelet precursor cells that undergo endomitosis. During this process, repeated rounds of DNA synthesis are characterized by lack of late anaphase and cytokinesis. Physiologically, the majority of the polyploid megakaryocytes in the bone marrow are cell cycle arrested. As previously reported, cyclin E is essential for megakaryocyte polyploidy; however, it has remained unclear whether up-regulated cyclin E is an inducer of polyploidy in vivo. We found that cyclin E is up-regulated upon stimulation of primary megakaryocytes by thrombopoietin. Transgenic mice in which elevated cyclin E expression is targeted to megakaryocytes display an increased ploidy profile. Examination of S phase markers, specifically proliferating cell nuclear antigen, cyclin A, and 5-bromo-2-deoxyuridine reveals that cyclin E promotes progression to S phase and cell cycling. Interestingly, analysis of Cdc6 and Mcm2 indicates that cyclin E mediates its effect by promoting the expression of components of the pre-replication complex. Furthermore, we show that up-regulated cyclin E results in the up-regulation of cyclin B1 levels, suggesting an additional mechanism of cyclin E-mediated ploidy increase. These findings define a key role for cyclin E in promoting megakaryocyte entry into S phase and hence, increase in the number of cell cycling cells and in augmenting polyploidization.
Cyclin B
Cyclin A
Cyclin E
Cyclin D
Cyclin A2
Cyclin B1
Cyclin D2
Cyclin D3
Cite
Citations (43)
Cyclin D
Cyclin D2
Cyclin A
Cyclin B
Cyclin A2
Cyclin E
Cyclin D3
Cite
Citations (6)