scholarly journals The LMO2 oncogene regulates DNA replication in hematopoietic cells

2016 ◽  
Vol 113 (5) ◽  
pp. 1393-1398 ◽  
Author(s):  
Marie-Claude Sincennes ◽  
Magali Humbert ◽  
Benoît Grondin ◽  
Véronique Lisi ◽  
Diogo F. T. Veiga ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Sequences ◽  
Lymphoblastic Leukemia ◽  
Ectopic Expression ◽  
Dna Polymerase Delta ◽  
Thymocyte Development ◽  
Erythroid Progenitors ◽  
Acute Leukemias ◽  
Synthetic Dna

Oncogenic transcription factors are commonly activated in acute leukemias and subvert normal gene expression networks to reprogram hematopoietic progenitors into preleukemic stem cells, as exemplified by LIM-only 2 (LMO2) in T-cell acute lymphoblastic leukemia (T-ALL). Whether or not these oncoproteins interfere with other DNA-dependent processes is largely unexplored. Here, we show that LMO2 is recruited to DNA replication origins by interaction with three essential replication enzymes: DNA polymerase delta (POLD1), DNA primase (PRIM1), and minichromosome 6 (MCM6). Furthermore, tethering LMO2 to synthetic DNA sequences is sufficient to transform these sequences into origins of replication. We next addressed the importance of LMO2 in erythroid and thymocyte development, two lineages in which cell cycle and differentiation are tightly coordinated. Lowering LMO2 levels in erythroid progenitors delays G1-S progression and arrests erythropoietin-dependent cell growth while favoring terminal differentiation. Conversely, ectopic expression in thymocytes induces DNA replication and drives these cells into cell cycle, causing differentiation blockade. Our results define a novel role for LMO2 in directly promoting DNA synthesis and G1-S progression.

A phase I trial of palbociclib in combination with dexamethasone in relapsed or refractory adult B-cell acute lymphoblastic leukemia (ALL).

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. TPS7065-TPS7065 ◽  
Author(s):  
Margaret T. Kasner ◽  
Lindsay Wilde ◽  
Gina Keiffer ◽  
Neil David Palmisiano ◽  
Bruno Calabretta
Keyword(s):  
Cell Cycle ◽  
Phase I ◽  
B Cell ◽  
Cell Cycle Arrest ◽  
Lymphoblastic Leukemia ◽  
Ectopic Expression ◽  
Maximum Tolerated Dose ◽  
Cyclin D3 ◽  
Cycle Arrest ◽  
Dose Limiting Toxicity

TPS7065 Background: c-Myb is a DNA-binding transcription factor that is highly expressed in immature hematopoietic cells. c-Myb and its products are essential in regulating normal hematopoiesis and influencing leukemogenesis. Knockdown of c-Myb causes cell cycle arrest and apoptosis in pre-B-ALL cells. The effects of c-Myb depend on transcriptional regulation of CDK6 and Bcl-2. c-Myb-silenced Ph+ ALL cells exhibit Rb-dependent cell cycle arrest and apoptosis, both of which are rescued by ectopic expression of cyclin D3, CDK6, and Bcl-2 expression. Preclinical studies suggest that the cytotoxic activity of dexamethasone in ALL cells may be due to decreased c-Myb expression and reduced Bcl-2 levels. Thus, the novel combination of palbociclib, a small molecule CDK4/6 inhibitor, and dexamethasone is a logical approach for the treatment of B-cell ALL. Methods: This is a single arm, phase I, dose escalation study with a traditional 3+3 design. Adult patients with relapsed or refractory B-cell ALL are eligible. Patients with Ph+ ALL must be refractory to or intolerant of standard tyrosine kinase inhibitor therapy. Patients receive a 1-week lead-in of palbociclib alone followed by induction with 4 weeks of palbociclib and dexamethasone. If an adequate response is seen, patients move to maintenance therapy, which consists of 1 week of palbociclib plus dexamethasone followed by 3 weeks of palbociclib alone. Treatment continues until disease progression, dose limiting toxicity, or availability of an alternative therapy. The primary endpoints are dose limiting toxicity and maximum tolerated dose of palbociclib and dexamethasone. Correlative studies, which are performed on pretreatment, day +1 and day +8 samples, include RB phosphorylation and FOXM1 expression as measures of palbociclib activity; CD19+ cell gene expression profiling of (1) p21 expression as an indicator of cell cycle activity, (2) S-Phase, Annexin V/Caspase 3 activation as indicators of proliferation and apoptosis and (3) Myb and Bcl-2 expression as indicators of dexamethasone sensitivity. Cohort 1 is currently enrolling. Once a maximum tolerated dose is established, an expansion cohort is planned. Clinical trial information: NCT03472573.

scholarly journals Interphase Cell Cycle Dynamics of a Late-Replicating, Heterochromatic Homogeneously Staining Region: Precise Choreography of Condensation/Decondensation and Nuclear Positioning

1998 ◽  
Vol 140 (5) ◽  
pp. 975-989 ◽  
Author(s):  
Gang Li ◽  
Gail Sudlow ◽  
Andrew S. Belmont
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Sequences ◽  
Large Scale ◽  
S Phase ◽  
Interphase Cell ◽  
Compact Mass ◽  
Lac Operator ◽  
Cell Cycle Dynamics

Recently we described a new method for in situ localization of specific DNA sequences, based on lac operator/repressor recognition (Robinett, C.C., A. Straight, G. Li, C. Willhelm, G. Sudlow, A. Murray, and A.S. Belmont. 1996. J. Cell Biol. 135:1685–1700). We have applied this methodology to visualize the cell cycle dynamics of an ∼90 Mbp, late-replicating, heterochromatic homogeneously staining region (HSR) in CHO cells, combining immunostaining with direct in vivo observations. Between anaphase and early G1, the HSR extends approximately twofold to a linear, ∼0.3-μm-diam chromatid, and then recondenses to a compact mass adjacent to the nuclear envelope. No further changes in HSR conformation or position are seen through mid-S phase. However, HSR DNA replication is preceded by a decondensation and movement of the HSR into the nuclear interior 4–6 h into S phase. During DNA replication the HSR resolves into linear chromatids and then recondenses into a compact mass; this is followed by a third extension of the HSR during G2/ prophase. Surprisingly, compaction of the HSR is extremely high at all stages of interphase. Preliminary ultrastructural analysis of the HSR suggests at least three levels of large-scale chromatin organization above the 30-nm fiber.

Tal1 and a DNA Binding Mutant (Tal1R188G;R189G) Cooperate with LMO2 To Induce Leukemia in Mice.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1414-1414
Author(s):  
Kyle M. Draheim ◽  
Kimberly Erdkamp ◽  
Eward Arous ◽  
Jennifer A. Calvo ◽  
Michelle A. Kelliher
Keyword(s):  
T Cell ◽  
Dna Binding ◽  
Transgenic Mice ◽  
Target Genes ◽  
Lymphoblastic Leukemia ◽  
Ectopic Expression ◽  
Thymocyte Development ◽  
Binding Properties ◽  
Transcriptional Complex ◽  
Dna Binding Properties

Abstract LMO2 is a member of the “LIM only” protein family and required for primitive erythropoiesis and adult vasculogenesis and angiogenesis. In erythroid cells, LMO2 interacts with TAL1 and E47 and LDB1 and GATA-1, thereby forming a transcriptional complex whose target genes include EKLF, CKIT, and p4.2 (protein 4.2). LMO2 was first implicated in leukemogenesis when it was identified in chromosomal translocations t(11;14)(p13;q11) and t(7;11)(q35;p13) found in T cell acute lymphoblastic leukemia (T-ALL) patients. Ectopic expression of LMO2 in mice recapitulates the human disease, albeit at low penetrance and following a long latency. LMO2 has been shown to synergize with TAL1, yet the mechanism of oncogene cooperativity is unknown. Two models have been proposed: the first suggests that LMO2 and TAL1 synergize by forming an active transcriptional complex that induces expression of target genes such as retinaldehyde dehydrogenase 2 (RALDH2) and TALLA1 (a surface marker of T-ALL). The second model proposes that LMO2 and TAL1 sequester the E47/HEB heterodimer, resulting in inhibition of E47/HEB-mediated transcription. To distinguish between these models, we mated our Tal1 transgenic mice and our DNA binding mutant of Tal1(R188G:R189G) with Lmo2 transgenic mice. As expected, transgenic expression of Lmo2 induced disease in 23% of mice after 302 days. Similar to published studies, Tal1 and Lmo2 expression dramatically inhibited thymocyte development and induced T cell leukemia in 100% of the mice with a mean latency of 108 days. To test whether the DNA binding properties of tal1 were required to cooperate with LMO2, we mated mice expressing a DNA binding mutant of Tal1(R188G;R189G) with Lmo2 transgenic mice and found that tumors were induced with similar kinetics; 100% of mice developed disease with an average latency of 107 days. These data suggest LMO2 does not require the DNA-binding properties of Tal1 to induce leukemia in mice and support the model that LMO2 contributes to leukemia through E47/HEB sequestration and inhibition.

microRNA-452 exerts growth-suppressive activity against T-cell acute lymphoblastic leukemia

2018 ◽  
Vol 66 (4) ◽  
pp. 773-779 ◽  
Author(s):  
Haihao Wang ◽  
Qiannan Guo ◽  
Guizhi Zhu ◽  
Shuo Zhu ◽  
Peiwen Yang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Lymph Node ◽  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Lymphoblastic Leukemia ◽  
Ectopic Expression ◽  
Cell Cycle Distribution ◽  
Suppressive Activity ◽  
Hematological Cancers ◽  
Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological cancer. Although microRNA (miR)-452 serves as a tumor suppressor in multiple solid tumors, its expression and function in hematological cancers including T-ALL is largely unknown. We measured the expression of miR-452 in 38 T-ALL and 22 normal lymph node samples by real-time PCR analysis. The methylation levels in the promoter of miR-452 were determined using MethyLight assay. The effects of miR-452 overexpression on proliferation, cell cycle distribution, and tumorigenesis were explored. It was found that miR-452 expression levels were significantly lower in T-ALL specimens than in normal lymph node biopsies (P=0.0079). T-ALL specimens had a significantly higher methylation level in the promoter of miR-452 than normal lymph node tissues (P=0.0014). Consistently, miR-452 was downregulated in Jurkat and Molt-4 T-ALL cells, whose expression was restored after treatment with a demethylation agent 5-aza-2′-deoxycytidine. Ectopic expression of miR-452 inhibited the proliferation of Jurkat and Molt-4 cells and induced a G0/G1 cell cycle arrest. Overexpression of miR-452 suppressed the protein expression of BMI1 in T-ALL cells. Rescue experiments revealed that overexpression of BMI1 partially reversed the growth-suppressive effect of miR-452 on T-ALL cells. Xenograft tumor studies confirmed that overexpression of miR-452 suppressed tumor growth in nude mice and reduced the expression of BMI1. Collectively, miR-452 is epigenetically silenced and targets BMI1 to exert a growth suppressive activity in T-ALL. Restoration of miR-452 expression may represent a promising therapeutic strategy for this malignancy.

scholarly journals Replication and Control of Circular Bacterial Plasmids

1998 ◽  
Vol 62 (2) ◽  
pp. 434-464 ◽  
Author(s):  
Gloria del Solar ◽  
Rafael Giraldo ◽  
María Jesús Ruiz-Echevarría ◽  
Manuel Espinosa ◽  
Ramón Díaz-Orejas
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Polymerase ◽  
Dna Sequences ◽  
Antisense Rna ◽  
Bacterial Population ◽  
Replication Initiation ◽  
Plasmid Replication ◽  
Genetic Elements ◽  
Bacterial Plasmids

SUMMARY An essential feature of bacterial plasmids is their ability to replicate as autonomous genetic elements in a controlled way within the host. Therefore, they can be used to explore the mechanisms involved in DNA replication and to analyze the different strategies that couple DNA replication to other critical events in the cell cycle. In this review, we focus on replication and its control in circular plasmids. Plasmid replication can be conveniently divided into three stages: initiation, elongation, and termination. The inability of DNA polymerases to initiate de novo replication makes necessary the independent generation of a primer. This is solved, in circular plasmids, by two main strategies: (i) opening of the strands followed by RNA priming (theta and strand displacement replication) or (ii) cleavage of one of the DNA strands to generate a 3′-OH end (rolling-circle replication). Initiation is catalyzed most frequently by one or a few plasmid-encoded initiation proteins that recognize plasmid-specific DNA sequences and determine the point from which replication starts (the origin of replication). In some cases, these proteins also participate directly in the generation of the primer. These initiators can also play the role of pilot proteins that guide the assembly of the host replisome at the plasmid origin. Elongation of plasmid replication is carried out basically by DNA polymerase III holoenzyme (and, in some cases, by DNA polymerase I at an early stage), with the participation of other host proteins that form the replisome. Termination of replication has specific requirements and implications for reinitiation, studies of which have started. The initiation stage plays an additional role: it is the stage at which mechanisms controlling replication operate. The objective of this control is to maintain a fixed concentration of plasmid molecules in a growing bacterial population (duplication of the plasmid pool paced with duplication of the bacterial population). The molecules involved directly in this control can be (i) RNA (antisense RNA), (ii) DNA sequences (iterons), or (iii) antisense RNA and proteins acting in concert. The control elements maintain an average frequency of one plasmid replication per plasmid copy per cell cycle and can “sense” and correct deviations from this average. Most of the current knowledge on plasmid replication and its control is based on the results of analyses performed with pure cultures under steady-state growth conditions. This knowledge sets important parameters needed to understand the maintenance of these genetic elements in mixed populations and under environmental conditions.

scholarly journals Bone marrow mesenchymal stem cells from infants with MLL-AF4+ acute leukemia harbor and express the MLL-AF4 fusion gene

2009 ◽  
Vol 206 (13) ◽  
pp. 3131-3141 ◽  
Author(s):  
Pablo Menendez ◽  
Purificación Catalina ◽  
René Rodríguez ◽  
Gustavo J. Melen ◽  
Clara Bueno ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Mesenchymal Stem Cells ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
Ectopic Expression ◽  
Fusion Genes ◽  
Acute Leukemias ◽  
Cellular Origin ◽  
Marrow Mesenchymal Stem Cells

MLL-AF4 fusion is a hallmark genetic abnormality in infant B-acute lymphoblastic leukemia (B-ALL) known to arise in utero. The cellular origin of leukemic fusion genes during human development is difficult to ascertain. The bone marrow (BM) microenvironment plays an important role in the pathogenesis of several hematological malignances. BM mesenchymal stem cells (BM-MSC) from 38 children diagnosed with cytogenetically different acute leukemias were screened for leukemic fusion genes. Fusion genes were absent in BM-MSCs of childhood leukemias carrying TEL-AML1, BCR-ABL, AML1-ETO, MLL-AF9, MLL-AF10, MLL-ENL or hyperdiploidy. However, MLL-AF4 was detected and expressed in BM-MSCs from all cases of MLL-AF4+ B-ALL. Unlike leukemic blasts, MLL-AF4+ BM-MSCs did not display monoclonal Ig gene rearrangements. Endogenous or ectopic expression of MLL-AF4 exerted no effect on MSC culture homeostasis. These findings suggest that MSCs may be in part tumor-related, highlighting an unrecognized role of the BM milieu on the pathogenesis of MLL-AF4+ B-ALL. MLL-AF4 itself is not sufficient for MSC transformation and the expression of MLL-AF4 in MSCs is compatible with a mesenchymal phenotype, suggesting a differential impact in the hematopoietic system and mesenchyme. The absence of monoclonal rearrangements in MLL-AF4+ BM-MSCs precludes the possibility of cellular plasticity or de-differentiation of B-ALL blasts and suggests that MLL-AF4 might arise in a population of prehematopoietic precursors.

scholarly journals Absence of Wee1 ensures the meiotic cell cycle in Xenopus oocytes

2000 ◽  
Vol 14 (3) ◽  
pp. 328-338
Author(s):  
Nobushige Nakajo ◽  
Satoshi Yoshitome ◽  
Jun Iwashita ◽  
Maki Iida ◽  
Katsuhiro Uto ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Interphase Nucleus ◽  
Xenopus Oocytes ◽  
Ectopic Expression ◽  
S Phase ◽  
Translational Repression ◽  
Meiotic Cell ◽  
Mitotic Inhibitor ◽  
Meiosis I

Meiotic cells undergo two successive divisions without an intervening S phase. However, the mechanism of S-phase omission between the two meiotic divisions is largely unknown. Here we show that Wee1, a universal mitotic inhibitor, is absent in immature (but not mature)Xenopus oocytes, being down-regulated specifically during oogenesis; this down-regulation is most likely due to a translational repression. Even the modest ectopic expression of Wee1 in immature (meiosis I) oocytes can induce interphase nucleus reformation and DNA replication just after meiosis I. Thus, the presence of Wee1 during meiosis I converts the meiotic cell cycle into a mitotic-like cell cycle having S phase. In contrast, Myt1, a Wee1-related kinase, is present and directly involved in G2 arrest of immature oocytes, but its ectopic expression has little effect on the meiotic cell cycle. These results strongly indicate that the absence of Wee1 in meiosis I ensures the meiotic cell cycle in Xenopus oocytes. Based on these results and the data published previously in other organisms, we suggest that absence of Wee1 may be a well-conserved mechanism for omitting interphase or S phase between the two meiotic divisions.

scholarly journals Functional Interrogation of HOXA9 Regulome in MLLr Leukemia via Reporter-based CRISPR/Cas9 screen

2020 ◽  
Author(s):  
Hao Zhang ◽  
Yang Zhang ◽  
Shaela Wright ◽  
Judith Hyle ◽  
Lianzhong Zhao ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Myeloid Leukemia ◽  
Lymphoblastic Leukemia ◽  
Critical Role ◽  
Ectopic Expression ◽  
Leukemia Cell ◽  
Molecular Regulation ◽  
Acute Leukemias ◽  
Regulation Network ◽  
Human Acute Myeloid Leukemia

ABSTRACTAberrant HOXA9 expression is a hallmark of most aggressive acute leukemias, including human acute myeloid leukemia (AML) and subtypes of acute lymphoblastic leukemia (ALL). HOXA9 overexpression not only predicts poor diagnosis and outcome but also plays a critical role in leukemia transformation and maintenance. However, our current understanding of HOXA9 regulation in leukemia is limited, hindering development of therapeutic strategies to treat HOXA9-driven leukemia. To mitigate these challenges, we generated the first HOXA9-mCherry knock-in reporter in an MLL-rearranged (MLLr) B-ALL cell line to dissect HOXA9 regulation. By utilizing the reporter and CRISPR/Cas9 mediated screens, we identified transcription factors controlling HOXA9 expression, including a novel regulator, USF2 and its homolog USF1. USF1/USF2 depletion significantly down-regulated HOXA9 expression and impaired MLLr leukemia cell proliferation. Ectopic expression of HOXA9-MEIS1 fusion protein rescued the impaired leukemia cell proliferation upon USF2 loss. Cut&Run analysis revealed the direct occupancy of USF2 onto HOXA9 promoter in MLLr leukemia cells. Collectively, the HOXA9 reporter facilitated the functional interrogation of the HOXA9 regulome and has advanced our understanding of the molecular regulation network in HOXA9-driven leukemia.

scholarly journals Inhibition of cell proliferation by the Mad1 transcriptional repressor.

1996 ◽  
Vol 16 (6) ◽  
pp. 2796-2801 ◽  
Author(s):  
M F Roussel ◽  
R A Ashmun ◽  
C J Sherr ◽  
R N Eisenman ◽  
D E Ayer
Keyword(s):  
Cell Cycle ◽  
Dna Sequences ◽  
Cell Cycle Progression ◽  
Leucine Zipper ◽  
Ectopic Expression ◽  
Transcriptional Repressor ◽  
Cell Types ◽  
3T3 Cells ◽  
Cycle Progression ◽  
Tightly Coupled

Mad1 is a basic helix-loop-helix-leucine zipper protein that is induced upon differentiation of a number of distinct cell types. Mad1 dimerizes with Max and recognizes the same DNA sequences as do Myc:Max dimers. However, Mad1 and Myc appear to have opposing functions. Myc:Max heterodimers activate transcription while Mad:Max heterodimers repress transcription from the same promoter. In addition Mad1 has been shown to block the oncogenic activity of Myc. Here we show that ectopic expression of Mad1 inhibits the proliferative response of 3T3 cells to signaling through the colony-stimulating factor-1 (CSF-1) receptor. The ability of over-expressed Myc and cyclin D1 to complement the mutant CSF-1 receptor Y809F (containing a Y-to-F mutation at position 809) is also inhibited by Mad1. Cell cycle analysis of proliferating 3T3 cells transfected with Mad1 demonstrates a significant decrease in the fraction of cells in the S and G2/M phases and a concomitant increase in the fraction of G1 phase cells, indicating that Mad1 negatively influences cell cycle progression from the G1 to the S phase. Mutations in Mad1 which inhibit its activity as a transcription repressor also result in loss of Mad1 cell cycle inhibitory activity. Thus, the ability of Mad1 to inhibit cell cycle progression is tightly coupled to its function as a transcriptional repressor.

Sign in / Sign up

Export Citation Format

Share Document