scholarly journals Targeted polyubiquitylation of RASSF1C by the Mule and SCFβ-TrCP ligases in response to DNA damage

2011 ◽  
Vol 441 (1) ◽  
pp. 227-236 ◽  
Author(s):  
Xin Zhou ◽  
Ting-Ting Li ◽  
Xu Feng ◽  
Esther Hsiang ◽  
Yue Xiong ◽  
...  
Keyword(s):  
Dna Damage ◽  
Uv Irradiation ◽  
Glycogen Synthase ◽  
E3 Ligase ◽  
Cycle Arrest ◽  
Microtubule Stability ◽  
C Terminus ◽  
Stress Signals ◽  
Phosphoinositide 3 Kinase ◽  
And Function

RASSF1A [Ras association (RalGDS/AF-6) domain family member 1A] and RASSF1C are two ubiquitously expressed isoforms of the RASSF1 gene. The promoter of RASSF1A is frequently hypermethylated, resulting in inactivation in various human cancers. RASSF1A is implicated in the regulation of apoptosis, microtubule stability and cell cycle arrest. However, little is known about the regulation and function of RASSF1C. In the present study we show that exogenously expressed RASSF1C is a very unstable protein that is highly polyubiquitylated and degraded via the proteasome. Furthermore, RASSF1C degradation is enhanced when cells are exposed to stress signals, such as UV irradiation. Mule, a HECT (homologous with E6-associated protein C-terminus) family E3 ligase, but not SCFβ-TrCP [where SCF is Skp1 (S-phase kinase-associated protein 1)/cullin/F-box and β-TrCP is β-bransducin repeat-containing protein] or CUL4 (cullin 4)-DDB1 (damage-specific DNA-binding protein 1), is the E3 ligase for RASSF1C under normal conditions, whereas both Mule and SCFβ-TrCP target RASSF1C degradation in response to UV irradiation. GSK3 (glycogen synthase kinase 3) phosphorylates RASSF1C to promote RASSF1C degradation subsequently, which is negatively regulated by the PI3K (phosphoinositide 3-kinase)/Akt pathway. Thus the present study reveals a novel regulation of RASSF1C and the potentially important role of RASSF1C in DNA damage responses.

scholarly journals A small increase in CHEK1 activity leads to the arrest of the first zygotic division in human

2020 ◽  
Author(s):  
Beili Chen ◽  
Jianying Guo ◽  
Ting Wang ◽  
Qianhui Lee ◽  
Jia Ming ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Mitotic Checkpoint ◽  
Mitotic Division ◽  
Fine Tuning ◽  
Human Reproduction ◽  
Cycle Arrest ◽  
Assisted Human Reproduction ◽  
C Terminus ◽  
Low Concentrations

ABSTRACTThe first mitotic division in mammalian zygotes is unique. The fertilized egg reactivates its cell cycle, and the maternal and paternal genomes start to reprogram to become totipotent. The first division is very sensitive to a range of perturbations, particularly the DNA damage, leading to the embryo’s failure to enter the first mitosis. We discovered that a point mutation in the human CHEK1 gene resulted in an Arginine 442 to Glutamine change at the C-terminus of the CHEK1 protein. CHEK1 R442Q mutation caused the zygote to arrest just before the first division. Heterozygote individuals appeared to be healthy except that the female carriers are infertile. Expressing the corresponding mouse mutant Chk1 protein in zygotes also caused arrest before the first mitosis. Treating Chk1 R442Q mouse zygotes with low concentrations of CHEK1 inhibitor enabled the embryos to overcome the cell cycle arrest and resume normal development. Our results revealed an unexpected zygote mitotic checkpoint, which is extremely sensitive to the CHEK1 kinase activity. The fine-tuning of the DNA damage checkpoint permits the arrested one-cell embryos to overcome the first mitotic block and develop into healthy animals. These findings have important implications in assisted human reproduction.

scholarly journals ATM Activation and Its Recruitment to Damaged DNA Require Binding to the C Terminus of Nbs1

2005 ◽  
Vol 25 (13) ◽  
pp. 5363-5379 ◽  
Author(s):  
Zhongsheng You ◽  
Charly Chahwan ◽  
Julie Bailis ◽  
Tony Hunter ◽  
Paul Russell
Keyword(s):  
Dna Damage ◽  
Conformational Changes ◽  
Mrn Complex ◽  
Amino Terminal ◽  
Binding Domains ◽  
C Terminus ◽  
Acid Fragment ◽  
Egg Extracts ◽  
Phosphoinositide 3 Kinase ◽  
Damaged Dna

ABSTRACT ATM has a central role in controlling the cellular responses to DNA damage. It and other phosphoinositide 3-kinase-related kinases (PIKKs) have giant helical HEAT repeat domains in their amino-terminal regions. The functions of these domains in PIKKs are not well understood. ATM activation in response to DNA damage appears to be regulated by the Mre11-Rad50-Nbs1 (MRN) complex, although the exact functional relationship between the MRN complex and ATM is uncertain. Here we show that two pairs of HEAT repeats in fission yeast ATM (Tel1) interact with an FXF/Y motif at the C terminus of Nbs1. This interaction resembles nucleoporin FXFG motif binding to HEAT repeats in importin-β. Budding yeast Nbs1 (Xrs2) appears to have two FXF/Y motifs that interact with Tel1 (ATM). In Xenopus egg extracts, the C terminus of Nbs1 recruits ATM to damaged DNA, where it is subsequently autophosphorylated. This interaction is essential for ATM activation. A C-terminal 147-amino-acid fragment of Nbs1 that has the Mre11- and ATM-binding domains can restore ATM activation in an Nbs1-depleted extract. We conclude that an interaction between specific HEAT repeats in ATM and the C-terminal FXF/Y domain of Nbs1 is essential for ATM activation. We propose that conformational changes in the MRN complex that occur upon binding to damaged DNA are transmitted through the FXF/Y-HEAT interface to activate ATM. This interaction also retains active ATM at sites of DNA damage.

scholarly journals Biliary Epithelial Senescence in Liver Disease: There Will Be SASP

2021 ◽  
Vol 8 ◽  
Author(s):  
Vik Meadows ◽  
Leonardo Baiocchi ◽  
Debjyoti Kundu ◽  
Keisaku Sato ◽  
Yessenia Fuentes ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cellular Senescence ◽  
Liver Diseases ◽  
Acute Stress ◽  
Premature Senescence ◽  
Liver Size ◽  
Stress Signals ◽  
End Stage ◽  
And Function ◽  
The Impact

Cellular senescence is a pathophysiological phenomenon in which proliferative cells enter cell cycle arrest following DNA damage and other stress signals. Natural, permanent DNA damage can occur after repetitive cell division; however, acute stress or other injuries can push cells into premature senescence and eventually a senescence-associated secretory phenotype (SASP). In recent years, there has been increased evidence for the role of premature senescence in disease progression including diabetes, cardiac diseases, and end-stage liver diseases including cholestasis. Liver size and function change with aging, and presumably with increasing cellular senescence, so it is important to understand the mechanisms by which cellular senescence affects the functional nature of the liver in health and disease. As well, cells in a SASP state secrete a multitude of inflammatory and pro-fibrogenic factors that modulate the microenvironment. Cellular SASP and the associated, secreted factors have been implicated in the progression of liver diseases, such as cholestatic injury that target the biliary epithelial cells (i.e., cholangiocytes) lining the bile ducts. Indeed, cholangiocyte senescence/SASP is proposed to be a driver of disease phenotypes in a variety of liver injuries. Within this review, we will discuss the impact of cholangiocyte senescence and SASP in the pathogenesis of cholestatic disorders.

scholarly journals DNA Damage-Induced Cell Cycle Regulation and Function of Novel Chk2 Phosphoresidues

2006 ◽  
Vol 26 (21) ◽  
pp. 7832-7845 ◽  
Author(s):  
Giacomo Buscemi ◽  
Luigi Carlessi ◽  
Laura Zannini ◽  
Sofia Lisanti ◽  
Enrico Fontanella ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Ataxia Telangiectasia ◽  
Dna Double Strand Breaks ◽  
Independent Manner ◽  
Strand Breaks ◽  
Cycle Arrest ◽  
And Function ◽  
Cycle Regulation

ABSTRACT Chk2 kinase is activated by DNA damage to regulate cell cycle arrest, DNA repair, and apoptosis. Phosphorylation of Chk2 in vivo by ataxia telangiectasia-mutated (ATM) on threonine 68 (T68) initiates a phosphorylation cascade that promotes the full activity of Chk2. We identified three serine residues (S19, S33, and S35) on Chk2 that became phosphorylated in vivo rapidly and exclusively in response to ionizing radiation (IR)-induced DNA double-strand breaks in an ATM- and Nbs1-dependent but ataxia telangiectasia- and Rad3-related-independent manner. Phosphorylation of these residues, restricted to the G1 phase of the cell cycle, was induced by a higher dose of IR (>1 Gy) than that required for phosphorylation of T68 (0.25 Gy) and declined by 45 to 90 min, concomitant with a rise in Chk2 autophosphorylation. Compared to the wild-type form, Chk2 with alanine substitutions at S19, S33, and S35 (Chk2S3A) showed impaired dimerization, defective auto- and trans-phosphorylation activities, and reduced ability to promote degradation of Hdmx, a phosphorylation target of Chk2 and regulator of p53 activity. Besides, Chk2S3A failed to inhibit cell growth and, in response to IR, to arrest G1/S progression. These findings underscore the critical roles of S19, S33, and S35 and argue that these phosphoresidues may serve to fine-tune the ATM-dependent response of Chk2 to increasing amounts of DNA damage.

Sa1797 Cell Cycle Arrest, DNA Damage and Remodeling of the Colonic Epithelial Barrier Composition and Function Underlies DSS-Induced Colitis

2013 ◽  
Vol 144 (5) ◽  
pp. S-308
Author(s):  
Rizwan Ahmad ◽  
Zhimin Chen ◽  
Rupesh Chaturvedi ◽  
Keith T. Wilson ◽  
Punita Dhawan ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Arrest ◽  
Epithelial Barrier ◽  
Cycle Arrest ◽  
And Function

scholarly journals MDMX is essential for the regulation of p53 protein levels in the absence of a functional MDM2 C-terminal tail

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Jack D. Sanford ◽  
Jing Yang ◽  
Jing Han ◽  
Laura A. Tollini ◽  
Aiwen Jin ◽  
...  
Keyword(s):  
Dna Damage ◽  
Protein Expression ◽  
P53 Protein ◽  
Critical Role ◽  
E3 Ligase ◽  
Mouse Embryonic Fibroblast ◽  
Protein Levels ◽  
P53 Protein Expression ◽  
C Terminus

Abstract Background MDM2 is an E3 ubiquitin ligase that is able to ubiquitinate p53, targeting it for proteasomal degradation. Its homologue MDMX does not have innate E3 activity, but is able to dimerize with MDM2. Although mouse models have demonstrated both MDM2 and MDMX are individually essential for p53 regulation, the significance of MDM2-MDMX heterodimerization is only partially understood and sometimes controversial. MDM2C462A mice, where the C462A mutation abolishes MDM2 E3 ligase activity as well as its ability to dimerize with MDMX, die during embryogenesis. In contrast, the MDM2Y487A mice, where the Y487A mutation at MDM2 C-terminus significantly reduces its E3 ligase activity without disrupting MDM2-MDMX binding, survive normally even though p53 is expressed to high levels. This indicates that the MDM2-MDMX heterodimerization plays a critical role in the regulation of p53. However, it remains unclear whether MDMX is essential for the regulation of p53 protein levels in the context of an endogenous MDM2 C-terminal tail mutation. Results Here, we studied the significance of MDM2-MDMX binding in an MDM2 E3 ligase deficient context using the MDM2Y487A mouse embryonic fibroblast (MEF) cells. Surprisingly, down-regulation of MDMX in MDM2Y487A MEFs resulted in a significant increase of p53 protein levels. Conversely, ectopic overexpression of MDMX reduced p53 protein levels in MDM2Y487A MEFs. Mutations of the RING domain of MDMX prevented MDMX-MDM2 binding, and ablated MDMX-mediated suppression of p53 protein expression. Additionally, DNA damage treatment and nuclear sequestration of MDMX inhibited MDMX activity to suppress p53 protein expression. Conclusions These results suggest that MDMX plays a key role in suppressing p53 protein expression in the absence of normal MDM2 E3 ligase activity. We found that the ability of MDMX to suppress p53 levels requires MDM2 binding and its cytoplasmic localization, and this ability is abrogated by DNA damage. Hence, MDMX is essential for the regulation of p53 protein levels in the context of an MDM2 C-terminal mutation that disrupts its E3 ligase activity but not MDMX binding. Our study is the first to examine the role of MDMX in the regulation of p53 in the context of endogenous MDM2 C-terminal mutant MEF cells.

scholarly journals MDM2 Promotes Ubiquitination and Degradation of MDMX

2003 ◽  
Vol 23 (15) ◽  
pp. 5113-5121 ◽  
Author(s):  
Yu Pan ◽  
Jiandong Chen
Keyword(s):  
Dna Damage ◽  
Tumor Suppressor ◽  
E3 Ligase ◽  
Adenovirus Infection ◽  
Down Regulation ◽  
Present Evidence ◽  
Mdm2 Expression ◽  
Important Regulator ◽  
Stress Signals ◽  
Ligase Function

ABSTRACT The p53 tumor suppressor is regulated by MDM2-mediated ubiquitination and degradation. Mitogenic signals activate p53 by induction of ARF expression, which inhibits p53 ubiquitination by MDM2. Recent studies showed that the MDM2 homolog MDMX is also an important regulator of p53. We present evidence that MDM2 promotes MDMX ubiquitination and degradation by the proteasomes. This effect is stimulated by ARF and correlates with the ability of ARF to bind MDM2. Promotion of MDM2-mediated MDMX ubiquitination requires the N-terminal domain of ARF, which normally inhibits MDM2 ubiquitination of p53. An intact RING domain of MDM2 is also required, both to interact with MDMX and to provide E3 ligase function. Increase of MDM2 and ARF levels by DNA damage, recombinant ARF adenovirus infection, or inducible MDM2 expression leads to proteasome-mediated down-regulation of MDMX levels. Therefore, MDMX and MDM2 are coordinately regulated by stress signals. The ARF tumor suppressor differentially regulates the ability of MDM2 to promote p53 and MDMX ubiquitination and activates p53 by targeting both members of the MDM2 family.

DNA damage and osmotic regulation in the kidney

2005 ◽  
Vol 289 (1) ◽  
pp. F2-F7 ◽  
Author(s):  
Natalia I. Dmitrieva ◽  
Maurice B. Burg ◽  
Joan D. Ferraris
Keyword(s):  
Dna Damage ◽  
Cultured Cells ◽  
Osmotic Regulation ◽  
Dna Double Strand Breaks ◽  
Dna Breaks ◽  
Atm Kinase ◽  
Strand Breaks ◽  
Cycle Arrest ◽  
And Function

Renal medullary cells normally are exposed to extraordinarily high interstitial NaCl concentration as part of the urinary concentrating mechanism, yet they survive and function. Acute elevation of NaCl to a moderate level causes transient cell cycle arrest in culture. Higher levels of NaCl, within the range found in the inner medulla, cause apoptosis. Recently, it was surprising to discover that even moderately high levels of NaCl cause DNA double-strand breaks. The DNA breaks persist in cultured cells that are proliferating rapidly after adaptation to high NaCl, and DNA breaks normally are present in the renal inner medulla in vivo. High NaCl inhibits repair of broken DNA both in culture and in vivo, but the DNA is rapidly repaired if the level of NaCl is reduced. The inhibition of DNA repair is associated with suppressed activity of some DNA damage-response proteins like Mre11, Chk1, and H2AX but not that of others, like GADD45, p53, ataxia telangiectasia-mutated kinase (ATM), and Ku86. In this review, we consider possible mechanisms by which the renal cells escape the known dangerous consequences of persistent DNA damage. Furthermore, we consider that the persistent DNA damage may be a sensor of hypertonicity that activates ATM kinase to provide a signal that contributes to protective osmotic regulation.

scholarly journals Ubiquitin–proteasome degradation of serum- and glucocorticoid-regulated kinase-1 (SGK-1) is mediated by the chaperone-dependent E3 ligase CHIP

2006 ◽  
Vol 400 (2) ◽  
pp. 235-244 ◽  
Author(s):  
Larissa Belova ◽  
Sanjay Sharma ◽  
Deanna R. Brickley ◽  
Jeremy R. Nicolarsen ◽  
Cam Patterson ◽  
...  
Keyword(s):  
Insulin Signalling ◽  
Critical Role ◽  
E3 Ligase ◽  
Proteasomal Degradation ◽  
Interacting Protein ◽  
Protein Levels ◽  
C Terminus ◽  
Ubiquitin Proteasome ◽  
Steady State Levels ◽  
Phosphoinositide 3 Kinase

SGK-1 (serum- and glucocorticoid-regulated kinase-1) is a stress-induced serine/threonine kinase that is phosphorylated and activated downstream of PI3K (phosphoinositide 3-kinase). SGK-1 plays a critical role in insulin signalling, cation transport and cell survival. SGK-1 mRNA expression is transiently induced following cellular stress, and SGK-1 protein levels are tightly regulated by rapid proteasomal degradation. In the present study we report that SGK-1 forms a complex with the stress-associated E3 ligase CHIP [C-terminus of Hsc (heat-shock cognate protein) 70-interacting protein]; CHIP is required for both the ubiquitin modification and rapid proteasomal degradation of SGK-1. We also show that CHIP co-localizes with SGK-1 at or near the endoplasmic reticulum. CHIP-mediated regulation of SGK-1 steady-state levels alters SGK-1 kinase activity. These data suggest a model that integrates CHIP function with regulation of the PI3K/SGK-1 pathway in the stress response.

scholarly journals Posttranslational Modifications of Tubulin and the Polarized Transport of Kinesin-1 in Neurons

2010 ◽  
Vol 21 (4) ◽  
pp. 572-583 ◽  
Author(s):  
Jennetta W. Hammond ◽  
Chun-Fang Huang ◽  
Stefanie Kaech ◽  
Catherine Jacobson ◽  
Gary Banker ◽  
...  
Keyword(s):  
Posttranslational Modifications ◽  
Hippocampal Neurons ◽  
Neuronal Development ◽  
Glycogen Synthase ◽  
Morphological Differentiation ◽  
Tubulin Acetylation ◽  
Microtubule Stability ◽  
Polarized Transport ◽  
And Function ◽  
Selective Accumulation

Polarized transport by microtubule-based motors is critical for neuronal development and function. Selective translocation of the Kinesin-1 motor domain is the earliest known marker of axonal identity, occurring before morphological differentiation. Thus, Kinesin-1–mediated transport may contribute to axonal specification. We tested whether posttranslational modifications of tubulin influence the ability of Kinesin-1 motors to distinguish microtubule tracks during neuronal development. We detected no difference in microtubule stability between axons and minor neurites in polarized stage 3 hippocampal neurons. In contrast, microtubule modifications were enriched in a subset of neurites in unpolarized stage 2 cells and the developing axon in polarized stage 3 cells. This enrichment correlated with the selective accumulation of constitutively active Kinesin-1 motors. Increasing tubulin acetylation, without altering the levels of other tubulin modifications, did not alter the selectivity of Kinesin-1 accumulation in polarized cells. However, globally enhancing tubulin acetylation, detyrosination, and polyglutamylation by Taxol treatment or inhibition of glycogen synthase kinase 3β decreased the selectivity of Kinesin-1 translocation and led to the formation of multiple axons. Although microtubule acetylation enhances the motility of Kinesin-1, the preferential translocation of Kinesin-1 on axonal microtubules in polarized neuronal cells is not determined by acetylation alone but is probably specified by a combination of tubulin modifications.

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