scholarly journals BBX proteins promote HY5-mediated UVR8 signaling in Arabidopsis

2021 ◽  
Author(s):  
Roman Podolec ◽  
Timothee B. Wagnon ◽  
Manuela Leonardelli ◽  
Henrik Johansson ◽  
Roman Ulm
Keyword(s):  
Transcription Factors ◽  
Ubiquitin Ligase ◽  
Red Light ◽  
E3 Ubiquitin Ligase ◽  
Transcriptional Regulator ◽  
Cooperative Binding ◽  
Uv Resistance ◽  
Hypocotyl Growth ◽  
Rate Limiting ◽  
Pigment Accumulation

Plants undergo photomorphogenic development in the presence of light. Photomorphogenesis is repressed by the E3 ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), which binds substrates through their valine-proline (VP) motifs. The UV RESISTANCE LOCUS8 (UVR8) photoreceptor senses UV-B and inhibits COP1 through cooperative binding of its own VP motif mimicry and its photosensing core to COP1, thereby preventing COP1 binding to substrates, including the bZIP transcriptional regulator ELONGATED HYPOCOTYL5 (HY5). As a key promoter of visible light and UV-B photomorphogenesis, HY5 functions together with the B-box family transcription factors BBX20-22 that were recently described as HY5 rate-limiting coactivators under red light. Here we describe a hypermorphic bbx21-3D mutant with enhanced photomorphogenesis, which carries a proline-314 to leucine mutation in the VP motif that impairs interaction with and regulation through COP1. We show that BBX21 and BBX22 are UVR8-dependently stabilized after UV-B exposure, which is counteracted by a repressor induced by HY5/BBX activity. bbx20 bbx21 bbx22 mutants under UV-B are impaired in hypocotyl growth inhibition, photoprotective pigment accumulation, and expression of several HY5-dependent genes. We conclude that BBX20-22 importantly contribute to HY5 activity in a subset of UV-B responses, but that additional, presently unknown coactivators for HY5 are functional in early UVR8 signaling.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

2019 ◽  
Vol 19 (1) ◽  
pp. 51-78 ◽  
Author(s):  
Ota Fuchs
Keyword(s):  
Clinical Trials ◽  
Transcription Factors ◽  
Ubiquitin Ligase ◽  
Mononuclear Cells ◽  
E3 Ubiquitin Ligase ◽  
Lymphocytic Leukemia ◽  
Monocarboxylate Transporter ◽  
Immunomodulatory Drugs ◽  
Monocarboxylate Transporter 1 ◽  
Argonaute 2

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

scholarly journals The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Sam A Menzies ◽  
Norbert Volkmar ◽  
Dick JH van den Boomen ◽  
Richard T Timms ◽  
Anna S Dickson ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Critical Role ◽  
E3 Ubiquitin Ligase ◽  
E3 Ligase ◽  
Editorial Note ◽  
Hmg Coa Reductase ◽  
Genome Wide ◽  
Cholesterol Biosynthetic Pathway ◽  
Coa Reductase ◽  
Rate Limiting

Mammalian HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the cholesterol biosynthetic pathway and the therapeutic target of statins, is post-transcriptionally regulated by sterol-accelerated degradation. Under cholesterol-replete conditions, HMGCR is ubiquitinated and degraded, but the identity of the E3 ubiquitin ligase(s) responsible for mammalian HMGCR turnover remains controversial. Using systematic, unbiased CRISPR/Cas9 genome-wide screens with a sterol-sensitive endogenous HMGCR reporter, we comprehensively map the E3 ligase landscape required for sterol-accelerated HMGCR degradation. We find that RNF145 and gp78 independently co-ordinate HMGCR ubiquitination and degradation. RNF145, a sterol-responsive ER-resident E3 ligase, is unstable but accumulates following sterol depletion. Sterol addition triggers RNF145 recruitment to HMGCR via Insigs, promoting HMGCR ubiquitination and proteasome-mediated degradation. In the absence of both RNF145 and gp78, Hrd1, a third UBE2G2-dependent E3 ligase, partially regulates HMGCR activity. Our findings reveal a critical role for the sterol-responsive RNF145 in HMGCR regulation and elucidate the complexity of sterol-accelerated HMGCR degradation.Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (<xref ref-type="decision-letter" rid="SA1">see decision letter</xref>).

scholarly journals The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1

2018 ◽  
Author(s):  
Sam A. Menzies ◽  
Norbert Volkmar ◽  
Dick J. van den Boomen ◽  
Richard T. Timms ◽  
Anna S. Dickson ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Critical Role ◽  
E3 Ubiquitin Ligase ◽  
E3 Ligase ◽  
Hmg Coa Reductase ◽  
Accelerated Degradation ◽  
Genome Wide ◽  
Cholesterol Biosynthetic Pathway ◽  
Coa Reductase ◽  
Rate Limiting

ABSTRACTHMG-CoA reductase (HMGCR), the rate-limiting enzyme of the cholesterol biosynthetic pathway and the therapeutic target of statins, is post-transcriptionally regulated by sterol-accelerated degradation. Under cholesterol-replete conditions, HMGCR is ubiquitinated and degraded, but the identity of the E3 ubiquitin ligase(s) responsible for mammalian HMGCR turnover remains controversial. Using systematic, unbiased CRISPR/Cas9 genome-wide screens with a sterol-sensitive endogenous HMGCR reporter, we comprehensively map the E3 ligase landscape required for sterol-accelerated HMGCR degradation. We find that RNF145 and gp78, independently co-ordinate HMGCR ubiquitination and degradation. RNF145, a sterol-responsive ER-resident E3 ligase, is unstable but accumulates following sterol depletion. Sterol addition triggers RNF145 recruitment to HMGCR and Insig-1, promoting HMGCR ubiquitination and proteasome-mediated degradation. In the absence of both RNF145 and gp78, Hrd1, a third UBE2G2-dependent ligase partially regulates HMGCR activity. Our findings reveal a critical role for the sterol-responsive RNF145 in HMGCR regulation and elucidate the complexity of sterol-accelerated HMGCR degradation.

scholarly journals LRR1-mediated replisome disassembly promotes DNA replication by recycling replisome components

2021 ◽  
Vol 220 (8) ◽  
Author(s):  
Yilin Fan ◽  
Marielle S. Köberlin ◽  
Nalin Ratnayeke ◽  
Chad Liu ◽  
Madhura Deshpande ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Cell Division ◽  
Dna Replication ◽  
Ubiquitin Ligase ◽  
Essential Gene ◽  
E3 Ubiquitin Ligase ◽  
S Phase ◽  
Replication Forks ◽  
G2 Phase ◽  
Rate Limiting

After two converging DNA replication forks meet, active replisomes are disassembled and unloaded from chromatin. A key process in replisome disassembly is the unloading of CMG helicases (CDC45–MCM–GINS), which is initiated in Caenorhabditis elegans and Xenopus laevis by the E3 ubiquitin ligase CRL2LRR1. Here, we show that human cells lacking LRR1 fail to unload CMG helicases and accumulate increasing amounts of chromatin-bound replisome components as cells progress through S phase. Markedly, we demonstrate that the failure to disassemble replisomes reduces the rate of DNA replication increasingly throughout S phase by sequestering rate-limiting replisome components on chromatin and blocking their recycling. Continued binding of CMG helicases to chromatin during G2 phase blocks mitosis by activating an ATR-mediated G2/M checkpoint. Finally, we provide evidence that LRR1 is an essential gene for human cell division, suggesting that CRL2LRR1 enzyme activity is required for the proliferation of cancer cells and is thus a potential target for cancer therapy.

scholarly journals A Novel Degron-mediated Degradation of the RTG Pathway Regulator, Mks1p, by SCFGrr1

2005 ◽  
Vol 16 (10) ◽  
pp. 4893-4904 ◽  
Author(s):  
Zhengchang Liu ◽  
Mário Spírek ◽  
Janet Thornton ◽  
Ronald A. Butow
Keyword(s):  
Transcription Factors ◽  
Ubiquitin Ligase ◽  
Positive Charge ◽  
E3 Ubiquitin Ligase ◽  
Retrograde Signaling ◽  
Yeast Cells ◽  
Leucine Rich Repeat ◽  
Negative Regulators ◽  
Acidic Domain ◽  
Lrr Domain

Yeast cells respond to mitochondrial dysfunction by altering the expression of a subset of nuclear genes, a process known as retrograde signaling (RS). RS terminates with two transcription factors, Rtg1p and Rtg3p. One positive regulator, Rtg2p, and four negative regulators, Lst8p, Mks1p, and the redundant 14-3-3 proteins, Bmh1p and Bmh2p, control RS upstream of Rtg1/3p. Mks1p is negatively regulated by binding to Rtg2p and positively regulated when bound to Bmh1/2p. Here we report that Grr1p, a component of the SCFGrr1 E3 ubiquitin ligase, modulates RS by affecting Mks1p levels. Grr1p polyubiquitinates Mks1p not bound to either Rtg2p or to Bmh1/2p, targeting it for degradation. An acidic domain region of Mks1p constitutes the portable Mks1p degron sequence. We have isolated dominant mutations in Grr1p leading to increased Mks1p degradation. These mutations result in a gain of positive charge on the concave surface of the leucine rich repeat (LRR) domain of Grr1p, the proposed substrate binding site. We propose that Mks1p is a central player of RS and is acted upon by multiple regulators of the pathway.

scholarly journals The Human Adenovirus Type 5 E4orf6/E1B55K E3 Ubiquitin Ligase Complex Can Mimic E1A Effects on E2F

mSphere ◽  
2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Frédéric Dallaire ◽  
Sabrina Schreiner ◽  
G. Eric Blair ◽  
Thomas Dobner ◽  
Philip E. Branton ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Dna Synthesis ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Viral Gene Expression ◽  
Adenovirus Vector ◽  
Human Adenovirus ◽  
Viral Gene ◽  
E2f Transcription Factors

ABSTRACT During the course of work on the adenovirus E3 ubiquitin ligase formed by the viral E4orf6 and E1B55K proteins, we found, very surprisingly, that expression of these species was sufficient to permit low levels of replication of an adenovirus vector lacking E1A, the central regulator of infection. E1A products uncouple E2F transcription factors from Rb repression complexes, thus stimulating viral gene expression and cell and viral DNA synthesis. We found that the E4orf6/E1B55K ligase mimics these functions. This finding is of significance because it represents an entirely new function for the ligase in regulating adenovirus replication. The human adenovirus E4orf6/E1B55K E3 ubiquitin ligase is well known to promote viral replication by degrading an increasing number of cellular proteins that inhibit the efficient production of viral progeny. We report here a new function of the adenovirus 5 (Ad5) viral ligase complex that, although at lower levels, mimics effects of E1A products on E2F transcription factors. When expressed in the absence of E1A, the E4orf6 protein in complex with E1B55K binds E2F, disrupts E2F/retinoblastoma protein (Rb) complexes, and induces hyperphosphorylation of Rb, leading to induction of viral and cellular DNA synthesis as well as stimulation of early and late viral gene expression and production of viral progeny of E1/E3-defective adenovirus vectors. These new and previously undescribed functions of the E4orf6/E1B55K E3 ubiquitin ligase could play an important role in promoting the replication of wild-type viruses. IMPORTANCE During the course of work on the adenovirus E3 ubiquitin ligase formed by the viral E4orf6 and E1B55K proteins, we found, very surprisingly, that expression of these species was sufficient to permit low levels of replication of an adenovirus vector lacking E1A, the central regulator of infection. E1A products uncouple E2F transcription factors from Rb repression complexes, thus stimulating viral gene expression and cell and viral DNA synthesis. We found that the E4orf6/E1B55K ligase mimics these functions. This finding is of significance because it represents an entirely new function for the ligase in regulating adenovirus replication.

scholarly journals BLADE-ON-PETIOLE proteins act in an E3 ubiquitin ligase complex to regulate PHYTOCHROME INTERACTING FACTOR 4 abundance

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Bo Zhang ◽  
Mattias Holmlund ◽  
Severine Lorrain ◽  
Mikael Norberg ◽  
László Bakó ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Flower Development ◽  
Red Light ◽  
E3 Ubiquitin Ligase ◽  
Plant Responses ◽  
Signaling Mechanism ◽  
Ubiquitin Ligase Complex ◽  
Molecular Determinants ◽  
Subsequent Degradation

Both light and temperature have dramatic effects on plant development. Phytochrome photoreceptors regulate plant responses to the environment in large part by controlling the abundance of PHYTOCHROME INTERACTING FACTOR (PIF) transcription factors. However, the molecular determinants of this essential signaling mechanism still remain largely unknown. Here, we present evidence that the BLADE-ON-PETIOLE (BOP) genes, which have previously been shown to control leaf and flower development in Arabidopsis, are involved in controlling the abundance of PIF4. Genetic analysis shows that BOP2 promotes photo-morphogenesis and modulates thermomorphogenesis by suppressing PIF4 activity, through a reduction in PIF4 protein level. In red-light-grown seedlings PIF4 ubiquitination was reduced in the bop2 mutant. Moreover, we found that BOP proteins physically interact with both PIF4 and CULLIN3A and that a CULLIN3-BOP2 complex ubiquitinates PIF4 in vitro. This shows that BOP proteins act as substrate adaptors in a CUL3BOP1/BOP2 E3 ubiquitin ligase complex, targeting PIF4 proteins for ubiquitination and subsequent degradation.

scholarly journals Functions of COP1/SPA E3 Ubiquitin Ligase Mediated by MpCRY in the Liverwort Marchantia Polymorpha under Blue Light

2021 ◽  
Vol 23 (1) ◽  
pp. 158
Author(s):  
Li Zhang ◽  
Tianhong Li ◽  
Shengzhong Su ◽  
Hao Peng ◽  
Sudi Li ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Blue Light ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Land Plants ◽  
Marchantia Polymorpha ◽  
Regulatory Pathway ◽  
Knock Out

COP1/SPA1 complex in Arabidopsis inhibits photomorphogenesis through the ubiquitination of multiple photo-responsive transcription factors in darkness, but such inhibiting function of COP1/SPA1 complex would be suppressed by cryptochromes in blue light. Extensive studies have been conducted on these mechanisms in Arabidopsis whereas little attention has been focused on whether another branch of land plants bryophyte utilizes this blue-light regulatory pathway. To study this problem, we conducted a study in the liverwort Marchantia polymorpha and obtained a MpSPA knock-out mutant, in which Mpspa exhibits the phenotype of an increased percentage of individuals with asymmetrical thallus growth, similar to MpCRY knock-out mutant. We also verified interactions of MpSPA with MpCRY (in a blue light-independent way) and with MpCOP1. Concomitantly, both MpSPA and MpCOP1 could interact with MpHY5, and MpSPA can promote MpCOP1 to ubiquitinate MpHY5 but MpCRY does not regulate the ubiquitination of MpHY5 by MpCOP1/MpSPA complex. These data suggest that COP1/SPA ubiquitinating HY5 is conserved in Marchantia polymorpha, but dissimilar to CRY in Arabidopsis, MpCRY is not an inhibitor of this process under blue light.

scholarly journals Targeting oncoproteins with a positive selection assay for protein degraders

2021 ◽  
Vol 7 (6) ◽  
pp. eabd6263
Author(s):  
Vidyasagar Koduri ◽  
Leslie Duplaquet ◽  
Benjamin L. Lampson ◽  
Adam C. Wang ◽  
Amin H. Sabet ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Small Molecules ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Signal To Noise ◽  
Independent Manner ◽  
Intracellular Proteins ◽  
Oncogenic Transcription Factor

Most intracellular proteins lack hydrophobic pockets suitable for altering their function with drug-like small molecules. Recent studies indicate that some undruggable proteins can be targeted by compounds that can degrade them. For example, thalidomide-like drugs (IMiDs) degrade the critical multiple myeloma transcription factors IKZF1 and IKZF3 by recruiting them to the cereblon E3 ubiquitin ligase. Current loss of signal (“down”) assays for identifying degraders often exhibit poor signal-to-noise ratios, narrow dynamic ranges, and false positives from compounds that nonspecifically suppress transcription or translation. Here, we describe a gain of signal (“up”) assay for degraders. In arrayed chemical screens, we identified novel IMiD-like IKZF1 degraders and Spautin-1, which, unlike the IMiDs, degrades IKZF1 in a cereblon-independent manner. In a pooled CRISPR-Cas9–based screen, we found that CDK2 regulates the abundance of the ASCL1 oncogenic transcription factor. This methodology should facilitate the identification of drugs that directly or indirectly degrade undruggable proteins.

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