scholarly journals A signature motif in LIM proteins mediates binding to checkpoint proteins and increases tumour radiosensitivity

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Xiaojie Xu ◽  
Zhongyi Fan ◽  
Chaoyang Liang ◽  
Ling Li ◽  
Lili Wang ◽  
...  
Keyword(s):  
Checkpoint Proteins ◽  
Signature Motif ◽  
Lim Proteins

scholarly journals Targeting DNA Repair and Chromatin Crosstalk in Cancer Therapy

Cancers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 381
Author(s):  
Danielle P. Johnson ◽  
Mahesh B. Chandrasekharan ◽  
Marie Dutreix ◽  
Srividya Bhaskara
Keyword(s):  
Dna Repair ◽  
Cancer Therapy ◽  
Therapeutic Intervention ◽  
Synthetic Lethality ◽  
Checkpoint Proteins ◽  
Cellular Processes ◽  
Repair Pathways ◽  
Made In

Aberrant DNA repair pathways that underlie developmental diseases and cancers are potential targets for therapeutic intervention. Targeting DNA repair signal effectors, modulators and checkpoint proteins, and utilizing the synthetic lethality phenomena has led to seminal discoveries. Efforts to efficiently translate the basic findings to the clinic are currently underway. Chromatin modulation is an integral part of DNA repair cascades and an emerging field of investigation. Here, we discuss some of the key advancements made in DNA repair-based therapeutics and what is known regarding crosstalk between chromatin and repair pathways during various cellular processes, with an emphasis on cancer.

207 Small molecule inhibitors of Sec61 cotranslational translocation regulate the phagocytosis checkpoint molecule CD47

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A223-A223
Author(s):  
Jennifer Whang ◽  
Andrea Fan ◽  
Christopher Kirk ◽  
Eric Lowe ◽  
Dustin McMinn ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Small Molecule ◽  
Immune Checkpoint ◽  
Small Molecule Inhibitors ◽  
Protein Translocation ◽  
Signal Sequence ◽  
Checkpoint Proteins ◽  
Cotranslational Translocation ◽  
Macrophage Phagocytosis ◽  
Immune Checkpoint Proteins

BackgroundMany tumor cells escape immune cell clearance by overexpressing CD47, a multi-pass transmembrane protein, which binds signal regulatory protein α (SIRPα) on macrophages leading to decreased phagocytic activity. Blockade of CD47/SIRPα interactions enhances macrophage phagocytosis and is being targeted with antibody-based drugs, some of which are used in combination therapies in clinical trials. A novel method to target CD47 is through the inhibition of cotranslational translocation of transmembrane proteins. Immediately after exiting the ribosome, signal sequences that are unique to each protein are directed through the Sec61 channel into the ER for extracellular expression.1 Several Sec61-targeting compounds have been identified to suppress translocation in a signal sequence-specific manner.2 We previously described Sec61 inhibitors capable of selectively targeting immune checkpoint proteins and enhancing T cell function.3 Here, we demonstrate the blockade of CD47 expression on tumor cells and enhancement of macrophage phagocytosis with small molecule inhibitors of Sec61.MethodsSec61-dependent expression of target proteins was assayed using HEK293 cells overexpressing constructs comprised of signal sequences fused to a luciferase reporter. Stimulated PBMCs or tumor cells were incubated with Sec61 inhibitors, and surface expression of checkpoint molecules were examined by flow cytometry. Necrotic and apoptotic cells were assessed by Annexin V and 7AAD labeling. Human CD14+ monocytes were differentiated to M1- or M2-type macrophages. Jurkat or SKBR3 cells were incubated with Sec61 inhibitors, labeled with a pH sensitive dye and co-cultured with macrophages to assess phagocytosis.ResultsWe identified Sec61 inhibitors that block select immune checkpoint proteins. Compounds demonstrated either selective or multi-target profiles in transient transfection screens, which was supported by decreased protein expression on activated T cells. KZR-9275 targeted multiple checkpoint molecules, including PD-1, LAG-3 and CD73, along with a potent inhibition of the CD47 signal sequence reporter. CD47 surface expression was decreased on Jurkat and SKBR3 cells following 72 hours of compound treatment. KZR-9275 treatment of SKBR3 cells induced a minor increase in apoptotic cells, which was not detected in Jurkat cells. Increased macrophage phagocytosis, especially with M2-type macrophages, was observed when Jurkat or SKBR3 cells were pre-treated with KZR-9275.ConclusionsOur findings demonstrate that Sec61 inhibitors can block the expression of CD47, a phagocytosis checkpoint protein, on tumor cells and subsequently modulate macrophage phagocytic activity. Small molecule inhibitors of Sec61 provide an opportunity to target multiple checkpoint proteins on various cell populations. Future in vivo tumor models will assess the efficacy of Sec61 inhibitors to provide combination-like therapy.ReferencesPark E, Rapoport TA. Mechanisms of Sec61/SecY-mediated protein translocation across membranes. Annu Rev Biophys 2012; 41:1–20.Van Puyenbroeck V, Vermeire K. Inhibitors of protein translocation across membranes of the secretory pathway: novel antimicrobial and anticancer agents. Cell Mol Life Sci 2018; 75:1541–1558.Whang J, Anderl J, Fan A, Kirk C, Lowe E, McMinn D, et al. Targeting multiple immune checkpoint proteins with novel small molecule inhibitors of Sec61-dependent cotranslational translocation. 34th Annual Meeting & Pre-Conference Programs of the Society for Immunotherapy of Cancer (SITC 2019): part 2. J Immunother Cancer 2019; 7: 283. Abstract 815.

scholarly journals Fission Yeast Rad26 Is a Regulatory Subunit of the Rad3 Checkpoint Kinase

2002 ◽  
Vol 13 (2) ◽  
pp. 480-492 ◽  
Author(s):  
Tom D. Wolkow ◽  
Tamar Enoch
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Fission Yeast ◽  
Complex Analysis ◽  
Kinase Activity ◽  
Regulatory Subunit ◽  
Kinase Activation ◽  
Checkpoint Proteins ◽  
Cycle Arrest ◽  
Phosphoinositide 3 Kinase

Fission yeast Rad3 is a member of a family of phosphoinositide 3-kinase -related kinases required for the maintenance of genomic stability in all eukaryotic cells. In fission yeast, Rad3 regulates the cell cycle arrest and recovery activities associated with the G2/M checkpoint. We have developed an assay that directly measures Rad3 kinase activity in cells expressing physiological levels of the protein. Using the assay, we demonstrate directly that Rad3 kinase activity is stimulated by checkpoint signals. Of the five other G2/M checkpoint proteins (Hus1, Rad1, Rad9, Rad17, and Rad26), only Rad26 was required for Rad3 kinase activity. Because Rad26 has previously been shown to interact constitutively with Rad3, our results demonstrate that Rad26 is a regulatory subunit, and Rad3 is the catalytic subunit, of the Rad3/Rad26 kinase complex. Analysis of Rad26/Rad3 kinase activation in rad26.T12, a mutant that is proficient for cell cycle arrest, but defective in recovery, suggests that these two responses to checkpoint signals require quantitatively different levels of kinase activity from the Rad3/Rad26 complex.

scholarly journals Distinct Chromosome Segregation Roles for Spindle Checkpoint Proteins

2002 ◽  
Vol 13 (9) ◽  
pp. 3029-3041 ◽  
Author(s):  
Cheryl D. Warren ◽  
D. Michelle Brady ◽  
Raymond C. Johnston ◽  
Joseph S. Hanna ◽  
Kevin G. Hardwick ◽  
...  
Keyword(s):  
Amino Acid ◽  
Chromosome Segregation ◽  
Chromosome Instability ◽  
Spindle Checkpoint ◽  
Adjacent Segment ◽  
Effect Analysis ◽  
Checkpoint Proteins ◽  
Chromosome Transmission ◽  
Acid Fragment ◽  
Molecular Functions

The spindle checkpoint plays a central role in the fidelity of chromosome transmission by ensuring that anaphase is initiated only after kinetochore-microtubule associations of all sister chromatid pairs are complete. In this study, we find that known spindle checkpoint proteins do not contribute equally to chromosome segregation fidelity in Saccharomyces cerevisiae. Loss of Bub1 or Bub3 protein elicits the largest effect. Analysis of Bub1p reveals the presence of two molecular functions. An N-terminal 608-amino acid (nonkinase) portion of the protein supports robust checkpoint activity, and, as expected, contributes to chromosome segregation. A C-terminal kinase-encoding segment independently contributes to chromosome segregation through an unknown mechanism. Both molecular functions depend on association with Bub3p. A 156-amino acid fragment of Bub1p functions in Bub3p binding and in kinetochore localization by one-hybrid assay. An adjacent segment is required for Mad1p binding, detected by deletion analysis and coimmunoprecipitation. Finally, overexpression of wild-type BUB1 or MAD3 genes leads to chromosome instability. Analysis of this activity indicates that the Bub3p-binding domain of Bub1p contributes to this phenotype through disruption of checkpoint activity as well as through introduction of kinetochore or spindle damage.

scholarly journals Cytoplasmic dynein participates in meiotic checkpoint inactivation in mouse oocytes by transporting cytoplasmic mitotic arrest-deficient (Mad) proteins from kinetochores to spindle poles

Reproduction ◽  
2007 ◽  
Vol 133 (4) ◽  
pp. 685-695 ◽  
Author(s):  
Dong Zhang ◽  
Shen Yin ◽  
Man-Xi Jiang ◽  
Wei Ma ◽  
Yi Hou ◽  
...  
Keyword(s):  
Spindle Checkpoint ◽  
Germinal Vesicle ◽  
Cytoplasmic Dynein ◽  
Mitotic Arrest ◽  
Checkpoint Proteins ◽  
Meiotic Progression ◽  
Spindle Poles ◽  
Anaphase Onset ◽  
Oocyte Meiosis ◽  
And Function

The present study was designed to investigate the localization and function of cytoplasmic dynein (dynein) during mouse oocyte meiosis and its relationship with two major spindle checkpoint proteins, mitotic arrest-deficient (Mad) 1 and Mad2. Oocytes at various stages during the first meiosis were fixed and immunostained for dynein, Mad1, Mad2, kinetochores, microtubules, and chromosomes. Some oocytes were treated with nocodazole before examination. Anti-dynein antibody was injected into the oocytes at germinal vesicle (GV) stage before the examination of its effects on meiotic progression or Mad1 and Mad2 localization. Results showed that dynein was present in the oocytes at various stages from GV to metaphase II and the locations of Mad1 and Mad2 were associated with dynein’s movement. Both Mad1 and Mad2 had two existing states: one existed in the cytoplasm (cytoplasmic Mad1 or cytoplasmic Mad2), which did not bind to kinetochores, while the other bound to kinetochores (kinetochore Mad1 or kinetochore Mad2). The equilibrium between the two states varied during meiosis and/or in response to the changes of the connection between microtubules and kinetochores. Cytoplasmic Mad1 and Mad2 recruited to chromosomes when the connection between microtubules and chromosomes was destroyed. Inhibition of dynein interferes with cytoplasmic Mad1 and Mad2 transportation from chromosomes to spindle poles, thus inhibits checkpoint silence and delays anaphase onset. These results indicate that dynein may play a role in spindle checkpoint inactivation.

scholarly journals Retracted: Three BUB1 and BUBR1/MAD3-related spindle assembly checkpoint proteins are required for accurate mitosis in Arabidopsis

2014 ◽  
Vol 205 (1) ◽  
pp. 202-215 ◽  
Author(s):  
Laetitia Paganelli ◽  
Marie-Cécile Caillaud ◽  
Michaël Quentin ◽  
Isabelle Damiani ◽  
Benjamin Govetto ◽  
...  
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Checkpoint Proteins

scholarly journals Mechanosensing through direct binding of tensed F-actin by LIM domains

2020 ◽  
Author(s):  
Xiaoyu Sun ◽  
Donovan Y. Z. Phua ◽  
Lucas Axiotakis ◽  
Mark A. Smith ◽  
Elizabeth Blankman ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Point Mutations ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
General Mechanism ◽  
Protein Protein Interaction ◽  
Cytoplasmic Actin ◽  
Lim Domains ◽  
Lim Proteins

SummaryMechanical signals transmitted through the cytoplasmic actin cytoskeleton must be relayed to the nucleus to control gene expression. LIM domains are protein-protein interaction modules found in cytoskeletal proteins and transcriptional regulators; however, it is unclear if there is a direct link between these two functions. Here we identify three LIM protein families (zyxin, paxillin, and FHL) whose members preferentially localize to the actin cytoskeleton in mechanically-stimulated cells through their tandem LIM domains. A minimal actin-myosin reconstitution system reveals that representatives of all three families directly bind F-actin only in the presence of mechanical force. Point mutations at a site conserved in each LIM domain of these proteins selectively disrupt tensed F-actin binding in vitro and cytoskeletal localization in cells, demonstrating a common, avidity-based mechanism. Finally, we find that binding to tensed F-actin in the cytoplasm excludes the cancer-associated transcriptional co-activator FHL2 from the nucleus in stiff microenvironments. This establishes direct force-activated F-actin binding by FHL2 as a mechanosensing mechanism. Our studies suggest that force-dependent sequestration of LIM proteins on the actin cytoskeleton could be a general mechanism for controlling nuclear localization to effect mechanical signaling.

Checkpoint proteins determine organismal stress resistance and lifespan in C. elegans

Toxicology ◽  
2006 ◽  
Vol 226 (1) ◽  
pp. 16
Author(s):  
Anders Olsen ◽  
Maithili C. Vantipalli ◽  
Glenda A. Walker ◽  
Gordon J. Lithgow
Keyword(s):  
Stress Resistance ◽  
Checkpoint Proteins ◽  
C Elegans
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