Browsing by Subject "Mitosis"

Now showing 1 - 7 of 7
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    A Mechanistic Approach to Identify Novel Therapeutic Drugs for Targeting FA-Disrupted Malignancies
    (2023-07) Sheth, Aditya Sukumar; Clapp, D. Wade; Vance, Gail; Angus, Steve; Herbert, Brittney-Shea
    The Fanconi anemia (FA) signaling network plays a critical role in maintaining genomic integrity during interphase and mitosis. Biallelic germline mutation of any of the 22 genes that constitute this pathway (FANCA-FANCW) results in Fanconi Anemia, a cancer predisposition syndrome characterized by congenital malformations, bone marrow failure, and pediatric acute myeloid leukemias (AMLs). Among the general population, acquired genetic disruptions of the FA pathway are found in 30% of all sporadic cancers and over 15% of sporadic pediatric AMLs underscoring the importance of this pathway in the prevention of malignant transformation. Therefore, the identification of precision therapies for FA-deficient AML is a critical need. The canonical tumor suppressive role of FA proteins in the repair of DNA damage during interphase is well established. We and others have uncovered the roles of FA proteins in mitotic regulation, suggesting additional mechanisms by which the FA pathway prevents genomic instability. Mutation of FANCA is the most common cause of FA and is one of the most frequently disrupted FA pathway genes in sporadic AML. To identify synthetic lethal targets of FANCA, we previously identified mitotic phospho-signaling pathways required for the survival of FANCA-/- patient-derived fibroblasts through a kinome-wide shRNA screen. We identified mitotic kinases CHEK1, PLK1, SLK, and TTK as potential targets, which suggests a mitosis-specific vulnerability of FA-deficient cells. These findings corroborate work by others who have identified synthetic lethal interactions between PLK1 and the FA pathway members, FANCG and BRCA1, suggesting that inactivation of the FA pathway may sensitize cancers to PLK1 inhibition. A more thorough understanding of FA pathway function in mitosis provides new insight into AML pathogenesis and suggests that genetic disruptions of the FA pathway may be predictive of sensitivity to PLK1 inhibition, providing a preclinical rationale for the development of precision therapies.
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    Genetic variants of SDCCAG8 and MAGI2 in mitosis‐related pathway genes are independent predictors of cutaneous melanoma‐specific survival
    (Wiley, 2021) He, Yuanmin; Liu, Hongliang; Luo, Sheng; Amos, Christopher I.; Lee, Jeffrey E.; Li, Xin; Nan, Hongmei; Wei, Qingyi; Epidemiology, Richard M. Fairbanks School of Public Health
    Mitosis is a prognostic factor for cutaneous melanoma (CM), but accurate mitosis detection in CM tissues is difficult. Therefore, the 8th Edition of the American Joint Committee on Cancer staging system has removed the mitotic rate as a category criterion of the tumor T-category, based on the evidence that the mitotic rate was not an independent prognostic factor for melanoma survival. As single-nucleotide polymorphisms (SNPs) have been shown to be potential predictors for cutaneous melanoma-specific survival (CMSS), we investigated the potential prognostic value of SNPs in mitosis-related pathway genes in CMSS by analyzing their associations with outcomes of 850 CM patients from The University of Texas MD Anderson Cancer Center in a discovery dataset and validated the findings in another dataset of 409 CM patients from the Harvard University Nurses' Health Study and Health Professionals Follow-up Study. In both datasets, we identified two SNPs (SDCCAG8 rs10803138 G>A and MAGI2 rs3807694 C>T) as independent prognostic factors for CMSS, with adjusted allelic hazards ratios of 1.49 (95% confidence interval = 1.17-1.90, P = .001) and 1.45 (1.13-1.86, P = .003), respectively. Furthermore, their combined unfavorable alleles also predicted a poor survival in both discovery and validation datasets in a dose-response manner (Ptrend = .0006 and .0001, respectively). Additional functional analysis revealed that both SDCCAG8 rs10803138 A and MAGI2 rs3807694 T alleles were associated with elevated mRNA expression levels in normal tissues. Therefore, these findings suggest that SDCCAG8 rs10803138 G>A and MAGI2 rs3807694 C>T are independent prognostic biomarkers for CMSS, possibly by regulating the mRNA expression of the corresponding genes involved in mitosis.
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    Histone variant H2B.Z acetylation is necessary for maintenance of Toxoplasma gondii biological fitness
    (Cold Spring Harbor Laboratory, 2023-02-24) Vanagas, Laura; Muñoz, Daniela; Cristaldi, Constanza; Ganuza, Agustina; Nájera, Rosario; Bonardi, Mabel C.; Turowski, Valeria R.; Guzman, Fanny; Deng, Bin; Kim, Kami; Sullivan, William J., Jr.; Angel, Sergio O.; Pharmacology and Toxicology, School of Medicine
    Through regulation of DNA packaging, histone proteins are fundamental to a wide array of biological processes. A variety of post-translational modifications (PTMs), including acetylation, constitute a proposed histone code that is interpreted by “reader” proteins to modulate chromatin structure. Canonical histones can be replaced with variant versions that add an additional layer of regulatory complexity. The protozoan parasite Toxoplasma gondii is unique among eukaryotes in possessing a novel variant of H2B designated H2B.Z. The combination of PTMs and the use of histone variants is important for gene regulation in T. gondii, offering new targets for drug development. In this work, T. gondii parasites were generated in which the 5 N-terminal acetylatable lysines in H2B.Z were mutated to either alanine (c-Myc-A) or arginine (c-Myc-R). c-Myc-A mutant only displayed a mild effect in its ability to kill mice. c-Myc-R mutant presented an impaired ability to grow and an increase in differentiation to latent bradyzoites. This mutant line was also more sensitive to DNA damage, displayed no virulence in mice, and provided protective immunity against future infection. While nucleosome composition was unaltered, key genes were abnormally expressed during in vitro bradyzoite differentiation. Our results show that the N-terminal positive charge patch of H2B.Z is important for these procceses. Pull down assays with acetylated N-terminal H2B.Z peptide and unacetylated one retrieved common and differential interactors. Acetylated peptide pulled down proteins associated with chromosome maintenance/segregation and cell cycle, opening the question of a possible link between H2B.Z acetylation status and mitosis.
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    Histone variant H2B.Z acetylation is necessary for maintenance of Toxoplasma gondii biological fitness
    (Elsevier, 2023) Vanagas, Laura; Muñoz, Daniela; Cristaldi, Constanza; Ganuza, Agustina; Nájera, Rosario; Bonardi, Mabel C.; Turowski, Valeria R.; Guzman, Fanny; Deng, Bin; Kim, Kami; Sullivan, William J., Jr.; Angel, Sergio O.; Pharmacology and Toxicology, School of Medicine
    Through regulation of DNA packaging, histone proteins are fundamental to a wide array of biological processes. A variety of post-translational modifications (PTMs), including acetylation, constitute a proposed histone code that is interpreted by "reader" proteins to modulate chromatin structure. Canonical histones can be replaced with variant versions that add an additional layer of regulatory complexity. The protozoan parasite Toxoplasma gondii is unique among eukaryotes in possessing a novel variant of H2B designated H2B.Z. The combination of PTMs and the use of histone variants are important for gene regulation in T. gondii, offering new targets for drug development. In this work, T. gondii parasites were generated in which the 5 N-terminal acetylatable lysines in H2B.Z were mutated to either alanine (c-Myc-A) or arginine (c-Myc-R). The c-Myc-A mutant displayed no phenotype over than a mild defect in its ability to kill mice. The c-Myc-R mutant presented an impaired ability to grow and an increase in differentiation to latent bradyzoites. The c-Myc-R mutant was also more sensitive to DNA damage, displayed no virulence in mice, and provided protective immunity against future infection. While nucleosome composition was unaltered, key genes were abnormally expressed during in vitro bradyzoite differentiation. Our results show that regulation of the N-terminal positive charge patch of H2B.Z is important for these processes. We also show that acetylated N-terminal H2B.Z interacts with some unique proteins compared to its unacetylated counterpart; the acetylated peptide pulled down proteins associated with chromosome maintenance/segregation and cell cycle, suggesting a link between H2B.Z acetylation status and mitosis.
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    INPP5E Preserves Genomic Stability through Regulation of Mitosis
    (American Society for Microbiology, 2017-03-15) Sierra Potchanant, Elizabeth A.; Cerabona, Donna; Sater, Zahi Abdul; He, Ying; Sun, Zejin; Gehlhausen, Jeff; Nalepa, Grzegorz; Department of Pediatrics, IU School of Medicine
    The partially understood phosphoinositide signaling cascade regulates multiple aspects of cellular metabolism. Previous studies revealed that INPP5E, the inositol polyphosphate-5-phosphatase that is mutated in the developmental disorders Joubert and MORM syndromes, is essential for the function of the primary cilium and maintenance of phosphoinositide balance in nondividing cells. Here, we report that INPP5E further contributes to cellular homeostasis by regulating cell division. We found that silencing or genetic knockout of INPP5E in human and murine cells impairs the spindle assembly checkpoint, centrosome and spindle function, and maintenance of chromosomal integrity. Consistent with a cell cycle regulatory role, we found that INPP5E expression is cell cycle dependent, peaking at mitotic entry. INPP5E localizes to centrosomes, chromosomes, and kinetochores in early mitosis and shuttles to the midzone spindle at mitotic exit. Our findings identify the previously unknown, essential role of INPP5E in mitosis and prevention of aneuploidy, providing a new perspective on the function of this phosphoinositide phosphatase in health and development.
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    Polo-like kinase 1 (Plk1) overexpression enhances ionizing radiation-induced cancer formation in mice
    (American Society for Biochemistry and Molecular Biology, 2017-10-20) Li, Zhiguo; Liu, Jinghui; Li, Jie; Kong, Yifan; Sandusky, George; Rao, Xi; Liu, Yunlong; Wan, Jun; Liu, Xiaoqi; Biochemistry and Molecular Biology, School of Medicine
    Polo-like kinase 1 (Plk1), a serine/threonine protein kinase normally expressed in mitosis, is frequently up-regulated in multiple types of human tumors regardless of the cell cycle stage. However, the causal relationship between Plk1 up-regulation and tumorigenesis is incompletely investigated. To this end, using a conditional expression system, here we generated Plk1 transgenic mouse lines to examine the role of Plk1 in tumorigenesis. Plk1 overexpression in mouse embryonic fibroblasts prepared from the transgenic mice led to aberrant mitosis followed by aneuploidy and apoptosis. Surprisingly, Plk1 overexpression had no apparent phenotypes in the mice. Given that no malignant tumor formation was observed even after a long period of Plk1 overexpression, we reasoned that additional factors are required for tumorigenesis in Plk1-overexpressing mice. Because Plk1 can directly participate in the regulation of the DNA damage response (DDR) pathway, we challenged Plk1-overexpressing mice with ionizing radiation (IR) and found that Plk1-overexpressing mice are much more sensitive to IR than their wild-type littermates. Analysis of tumor development in the Plk1-overexpressing mice indicated a marked decrease in the time required for tumor emergence after IR. At the molecular level, Plk1 overexpression led to reduced phosphorylation of the serine/threonine kinases ATM and Chk2 and of histone H2AX after IR treatment both in vivo and in vitro Furthermore, RNA-Seq analysis suggested that Plk1 elevation decreases the expression of several DDR genes. We conclude that Plk1 overexpression may contribute to tumor formation by both inducing chromosomal instability and suppressing the DDR pathway.
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    Role of the POZ zinc finger transcription factor FBI-1 in human and murine adipogenesis.
    (ASBMB, 2004-03-19) Laudes, Matthias; Christodoulides, Constantinos; Sewter, Ciaran; Rochford, Justin J.; Considine, Robert V.; Sethi, Jaswinder K.; Vidal-Puig, Antonio; O’Rahilly, Stephen; Department of Medicine, IU School of Medicine
    Poxvirus zinc finger (POZ) zinc finger domain transcription factors have been shown to play a role in the control of growth arrest and differentiation in several types of mesenchymal cells but not, as yet, adipocytes. We found that a POZ domain protein, factor that binds to inducer of short transcripts-1 (FBI-1), was induced during both murine and human preadipocyte differentiation with maximal expression levels seen at days 2-4. FBI-1 mRNA was expressed in human adipose tissue with the highest levels found in samples from morbidly obese subjects. Murine cell lines constitutively expressing FBI-1 showed evidence for accelerated adipogenesis with earlier induction of markers of differentiation and enhanced lipid accumulation, suggesting that FBI-1 may be an active participant in the differentiation process. Consistent with the properties of this family of proteins in other cell systems, 3T3L1 cells stably overexpressing FBI-1 showed reduced DNA synthesis and reduced expression of cyclin A, cyclin-dependent kinase 2, and p107, proteins known to be involved in the regulation of mitotic clonal expansion. In addition, FBI-1 reduced the transcriptional activity of the cyclin A promoter. Thus, FBI-1, a POZ zinc finger transcription factor, is induced during the early phases of human and murine preadipocyte differentiation where it may contribute to adipogenesis through influencing the switch from cellular proliferation to terminal differentiation.