The retinoblastoma orthologue, rblA, is a major regulator of S-phase, mitotic, and developmental gene expression in Dictyostelium
Ontology highlight
ABSTRACT:
ORGANISM(S): Dictyostelium discoideum
PROVIDER: GSE30368 | GEO | 2012/05/18
SECONDARY ACCESSION(S): PRJNA143419
REPOSITORIES: GEO
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Project description:The retinoblastoma tumour suppressor, Rb, has two major functions. First, it represses genes whose products are required for S-phase entry and progression, thus stabilizing cells in G1. Second, Rb synergizes with factors that induce cell cycle exit and terminal differentiation. Dictyostelium lacks a G1 phase in its cell cycle but it has a retinoblastoma orthologue, rblA. Using mRNA-Seq transcriptional profiling, we show that rblA strongly represses hundreds of genes whose products are involved in S-phase and mitosis. Both S-phase and mitotic genes are expressed at a single point in late G2 and again in mid-development, near the time when cell cycling is reactivated. RblA also activates a set of genes unique to slime moulds that function in terminal differentiation. Like its mammalian counterpart, Dictyostelium RblA plays a dual role, regulating cell cycle progression and transcriptional events leading to terminal differentiation. In the absence of a G1 phase, however, RblA functions in late G2 controlling the expression of both S-phase and mitotic genes. RNA was isolated from an rblA-disruptant and the parental strain when the cells were vegetatively growing or while the cells were developing (at the early culminant stage). Total RNA was also isolated from wild type cells synchronized using the cold-shock protocol (Maeda, J Gen Microbiol 132:1189-1196 (1986)). T0 to T13 represent the hours after the shift up from 9.5C to 22C, a regime that synchronizes the cells in the cell cycle.
2012-05-17 | E-GEOD-30368 | biostudies-arrayexpress
Project description:In metazoans, the retinoblastoma tumor suppressor has two major functions. In the first, it represses genes whose products are required for S-phase entry and S-phase progression, and thus stabilizes the G1 phase. In a second function, Rb synergizes with factors that induce cell cycle exit and terminal differentiation. Using mRNAseq and microarray transcriptional profiling, we show that rblA, the Rb ortholog of the Amebozoan Dictyostelium, has both of these functions. We characterize the action of rblA in the Dictyostelium cell cycle in detail, and in particular show that it represses not only S-phase genes but also almost all genes whose products are involved in mitosis. We compare rblA null mutants with their parent strain Ax2 at two developmental stages, vegetative growth and the preculminant stage of fruiting body formation; cell cycle genes show misregulation in the mutant at both stages.
2011-11-02 | E-TABM-1087 | biostudies-arrayexpress
Project description:The retinoblastoma (Rb) protein is a potent tumor suppressor which is known to negatively regulate the cell cycle as well as tumor progression. Phosphorylated Rb protein (pRb) has been demonstrated to be in-charge for the key G1 checkpoint, blocking entry into S-phase and thereby the cell growth. This study was designed to capture interacting protein partners of Rb1 as the cell cycle progresses. Rb1 expressing HEK-293 cells were cultured in light, medium and heavy SILAC labels to capture the changes in Rb1 interactome as the cell cycle progressed from G0 to G1S and then to G2 phase, respectively. This data might help in understanding the cell cycle regulatory effect of Rb1 protein and complement the available information on its interacting partners.
2017-09-14 | PXD007708 | Pride
Project description:The retinoblastoma tumor suppressor protein (Rb) regulates early G1 phase checkpoints, including the DNA damage response, as well as cell cycle exit and differentiation. The widely accepted model of G1 cell cycle progression proposes that cyclin D:Cdk4/6 partially inactivates the Rb tumor suppressor during early G1 phase by progressive multi-phosphorylation, termed hypo-phosphorylation, resulting in release of E2F transcription factors. However, this model remains largely unproven biochemically and the biologically active form(s) of Rb remains unknown. Here we find that Rb is un-phosphorylated in G0 cells and becomes exclusively mono-phosphorylated throughout all of early G1 phase by cyclin D:Cdk4/6. Early G1 phase mono-phosphorylated Rb is composed of 14 independent isoforms that are all targeted by the E1a oncoprotein, but each shows a preferential binding pattern to specific E2F1-4 transcription factors. At the late G1 Restriction Point, cyclin E:Cdk2 inactivates Rb by a quantum hyper-phosphorylation (>12 phosphates/Rb). Cells undergoing a DNA damage response activate cyclin D:Cdk4/6 to generate mono-phosphorylated Rb that regulates global transcription. In contrast, a non-phosphorylatable ?Cdk-Rb allele was non-functional for regulating a DNA damage response, but functional for driving cell cycle exit and differentiation during myogenesis. These observations fundamentally change our understanding of G1 cell cycle progression and show that there is no progressive multi-phosphorylation or hypo-phosphorylation inactivation of Rb during early G1 phase by cyclin D:Cdk4/6. Instead, cyclin D:Cdk4/6 generates functionally active, mono-phosphorylated Rb that is the only Rb isoform present in cells during early G1 phase.
2014-04-03 | GSE56453 | GEO
Project description:Cells switch between quiescence and proliferation states for maintaining tissue homeostasis and regeneration. At the restriction point (R-point), cells become irreversibly committed to the completion of the cell cycle independent of mitogen. The mechanism involving hyper-phosphorylation of retinoblastoma (Rb) and activation of transcription factor E2F is linked to the R-point passage. However, stress stimuli trigger exit from the cell cycle back to the mitogen-sensitive quiescent state after Rb hyper-phosphorylation but only until APC/CCdh1 inactivation. In this study, we developed a mathematical model to investigate the reversible transition between quiescence and proliferation in mammalian cells with respect to mitogen and stress signals. The model integrates the current mechanistic knowledge and accounts for the recent experimental observations with cells exiting quiescence and proliferating cells. We show that Cyclin E:Cdk2 couples Rb-E2F and APC/CCdh1 bistable switches and temporally segregates the R-point and the G1/S transition. A redox-dependent mutual antagonism between APC/CCdh1 and its inhibitor Emi1 makes the inactivation of APC/CCdh1 bistable. We show that the levels of Cdk inhibitor (CKI) and mitogen control the reversible transition between quiescence and proliferation. Further, we propose that shifting of the mitogen-induced transcriptional program to G2-phase in proliferating cells might result in an intermediate Cdk2 activity at the mitotic exit and in the immediate inactivation of APC/CCdh1. Our study builds a coherent framework and generates hypotheses that can be further explored by experiments.
2024-09-02 | BIOMD0000000954 | BioModels
Project description:The retinoblastoma tumor suppressor protein (Rb) regulates early G1 phase checkpoints, including the DNA damage response, as well as cell cycle exit and differentiation. The widely accepted model of G1 cell cycle progression proposes that cyclin D:Cdk4/6 partially inactivates the Rb tumor suppressor during early G1 phase by progressive multi-phosphorylation, termed hypo-phosphorylation, resulting in release of E2F transcription factors. However, this model remains largely unproven biochemically and the biologically active form(s) of Rb remains unknown. Here we find that Rb is un-phosphorylated in G0 cells and becomes exclusively mono-phosphorylated throughout all of early G1 phase by cyclin D:Cdk4/6. Early G1 phase mono-phosphorylated Rb is composed of 14 independent isoforms that are all targeted by the E1a oncoprotein, but each shows a preferential binding pattern to specific E2F1-4 transcription factors. At the late G1 Restriction Point, cyclin E:Cdk2 inactivates Rb by a quantum hyper-phosphorylation (>12 phosphates/Rb). Cells undergoing a DNA damage response activate cyclin D:Cdk4/6 to generate mono-phosphorylated Rb that regulates global transcription. In contrast, a non-phosphorylatable ?Cdk-Rb allele was non-functional for regulating a DNA damage response, but functional for driving cell cycle exit and differentiation during myogenesis. These observations fundamentally change our understanding of G1 cell cycle progression and show that there is no progressive multi-phosphorylation or hypo-phosphorylation inactivation of Rb during early G1 phase by cyclin D:Cdk4/6. Instead, cyclin D:Cdk4/6 generates functionally active, mono-phosphorylated Rb that is the only Rb isoform present in cells during early G1 phase. Global transcriptional analysis of murine embryonic fibroblasts (MEFs) with conditional deletion of the endogenous RB gene by treatment with cell permeable TAT-Cre. Comparison to unaltered MEFs and MEFs with physiological level of exogenous wildtype or phospho-mutant RB expressed at time of RB gene deletion.
2014-04-03 | E-GEOD-56453 | biostudies-arrayexpress
Project description:The prevailing dogma is that renewed mitogenic signaling is essential to traverse G1 phase of the cell cycle after each division. B lymphocytes undergo multiple mitotic divisions, termed clonal expansion, to expand antigen-specific cells that mediate effective immunity. We explored mechanisms by which primary murine B lymphocytes make cell division decisions. We demonstrate that commitment to DNA replication _S phase_ programs B cells to divide multiple times in the absence of overt mitogenic signaling. The extent of division is limited by cell death rather than by return to quiescence, and circumventing cell death permits up to 4 rounds of division in 72h. Mitogen-independent cell cycle progression is driven by unique S- and G2/M- like characteristics of the G1 phase of cells that have divided once, such as, large cell size, low levels of p27, phosphorylated Rb and expression of G2/M markers survivin, Cenp-A and Aim1/Aurora B. Pharmacologic inhibition of survivin blocked G1 progression in a B cell line and in primary B cells undergoing mitogen-independent division. These observations indicate that, in contrast to textbook models of the cell cycle, B cells inherit a partially active G1 phase after cell division that permits them to move quickly to the next S phase in the absence of exogenous G1 progression signals. Our studies provide direct evidence for Pardee’s hypothesis that retention of features of G2/M in post-mitotic cells could trigger a second round of cell cycle progression. We propose that these mechanisms may assist in rapid cell division without differentiation that is required for clonal expansion in response to antigens.
2022-04-29 | GSE195698 | GEO
Project description:Oncogene-induced senescence is an anti-proliferative stress response program that acts as a fail-safe mechanism to limit oncogenic transformation and is regulated by the retinoblastoma protein (RB) and p53 tumor suppressor pathways. We identify the atypical E2F family member E2F7 as the only E2F transcription factor potently upregulated during oncogene-induced senescence, a setting where it acts in response to p53 as a direct transcriptional target. Once induced, E2F7 binds and represses a series of E2F target genes and cooperates with RB to efficiently promote cell cycle arrest and limit oncogenic transformation. Disruption of RB triggers a further increase in E2F7, which induces a second cell cycle checkpoint that prevents unconstrained cell division despite aberrant DNA replication. Mechanistically, E2F7 compensates for the loss of RB in repressing mitotic E2F target genes. Examination of p53 binding in either growing or senescent IMR90 cells with different hairpins.
2012-12-05 | E-GEOD-42728 | biostudies-arrayexpress
Project description:Oncogene-induced senescence is an anti-proliferative stress response program that acts as a fail-safe mechanism to limit oncogenic transformation and is regulated by the retinoblastoma protein (RB) and p53 tumor suppressor pathways. We identify the atypical E2F family member E2F7 as the only E2F transcription factor potently upregulated during oncogene-induced senescence, a setting where it acts in response to p53 as a direct transcriptional target. Once induced, E2F7 binds and represses a series of E2F target genes and cooperates with RB to efficiently promote cell cycle arrest and limit oncogenic transformation. Disruption of RB triggers a further increase in E2F7, which induces a second cell cycle checkpoint that prevents unconstrained cell division despite aberrant DNA replication. Mechanistically, E2F7 compensates for the loss of RB in repressing mitotic E2F target genes. Examination of E2F7 binding in either growing or senescent IMR90 cells with different hairpins.
2012-08-25 | E-GEOD-40343 | biostudies-arrayexpress
Project description:Oncogene-induced senescence is an anti-proliferative stress response program that acts as a fail-safe mechanism to limit oncogenic transformation and is regulated by the retinoblastoma protein (RB) and p53 tumor suppressor pathways. We identify the atypical E2F family member E2F7 as the only E2F transcription factor potently upregulated during oncogene-induced senescence, a setting where it acts in response to p53 as a direct transcriptional target. Once induced, E2F7 binds and represses a series of E2F target genes and cooperates with RB to efficiently promote cell cycle arrest and limit oncogenic transformation. Disruption of RB triggers a further increase in E2F7, which induces a second cell cycle checkpoint that prevents unconstrained cell division despite aberrant DNA replication. Mechanistically, E2F7 compensates for the loss of RB in repressing mitotic E2F target genes.
2012-08-25 | GSE40349 | GEO