scholarly journals Fine‐Tuning of an Evolutionarily Conserved Histone Chaperone, FACT, by Ubiquitin‐Proteasome System, and its Targeting to the Active Gene by mRNA Capping Machinery to Regulate Transcriptional Elongation

2018 ◽  
Vol 32 (S1) ◽  
Author(s):  
Amala Kaja ◽  
Rwik Sen ◽  
Jannatul Ferdoush ◽  
Shweta Lahudkar ◽  
Priyanka Barman ◽  
...  
Keyword(s):  
Ubiquitin Proteasome System ◽  
Histone Chaperone ◽  
Fine Tuning ◽  
Transcriptional Elongation ◽  
Active Gene ◽  
Evolutionarily Conserved ◽  
Mrna Capping ◽  
Ubiquitin Proteasome

scholarly journals Fine-Tuning of FACT by the Ubiquitin Proteasome System in Regulation of Transcriptional Elongation

2016 ◽  
Vol 36 (11) ◽  
pp. 1691-1703 ◽  
Author(s):  
Rwik Sen ◽  
Jannatul Ferdoush ◽  
Amala Kaja ◽  
Sukesh R. Bhaumik
Keyword(s):  
Rna Polymerase Ii ◽  
Ubiquitin Proteasome System ◽  
Optimal Level ◽  
26S Proteasome ◽  
Fine Tuning ◽  
Transcriptional Elongation ◽  
Cellular Functions ◽  
Evolutionarily Conserved ◽  
Ubiquitin Proteasome ◽  
First Time

FACT (facilitateschromatintranscription), an evolutionarily conserved histone chaperone involved in transcription and other DNA transactions, is upregulated in cancers, and its downregulation is associated with cellular death. However, it is not clearly understood how FACT is fine-tuned for normal cellular functions. Here, we show that the FACT subunit Spt16 is ubiquitylated by San1 (an E3 ubiquitin ligase) and degraded by the 26S proteasome. Enhanced abundance of Spt16 in the absence of San1 impairs transcriptional elongation. Likewise, decreased abundance of Spt16 also reduces transcription. Thus, an optimal level of Spt16 is required for efficient transcriptional elongation, which is maintained by San1 via ubiquitylation and proteasomal degradation. Consistently, San1 associates with the coding sequences of active genes to regulate Spt16's abundance. Further, we found that enhanced abundance of Spt16 in the absence of San1 impairs chromatin reassembly at the coding sequence, similarly to the results seen following inactivation of Spt16. Efficient chromatin reassembly enhances the fidelity of transcriptional elongation. Taken together, our results demonstrate for the first time a fine-tuning of FACT by a ubiquitin proteasome system in promoting chromatin reassembly in the wake of elongating RNA polymerase II and transcriptional elongation, thus revealing novel regulatory mechanisms of gene expression.

scholarly journals The p97-UBXN1 complex regulates aggresome formation

2020 ◽  
Author(s):  
Sirisha Mukkavalli ◽  
Jacob Aaron Klickstein ◽  
Betty Ortiz ◽  
Peter Juo ◽  
Malavika Raman
Keyword(s):  
Protein Aggregation ◽  
Mammalian Cells ◽  
Proteasome Inhibition ◽  
Adaptor Proteins ◽  
Ubiquitin Proteasome System ◽  
Aaa Atpase ◽  
Evolutionarily Conserved ◽  
Ubiquitin Proteasome ◽  
Aggresome Formation

AbstractThe recognition and disposal of misfolded proteins are essential for the maintenance of cellular homeostasis. Perturbations in the pathways that promote degradation of aberrant proteins contribute to a variety of protein aggregation disorders broadly termed proteinopathies. It is presently unclear how diverse disease-relevant aggregates are recognized and processed for degradation. The p97 AAA-ATPase in combination with a host of adaptor proteins functions to identify ubiquitylated proteins and target them for degradation by the ubiquitin-proteasome system or through autophagy. Mutations in p97 cause multi-system proteinopathies; however, the precise defects underlying these disorders are unclear given the large number of pathways that rely on p97 function. Here, we systematically investigate the role of p97 and its adaptors in the process of formation of aggresomes which are membrane-less structures containing ubiquitylated proteins that arise upon proteasome inhibition. We demonstrate that p97 mediates both aggresome formation and clearance in proteasome-inhibited cells. We identify a novel and specific role for the p97 adaptor UBXN1 in the process of aggresome formation. UBXN1 is recruited to ubiquitin-positive aggresomes and UBXN1 knockout cells are unable to form a single aggresome, and instead display dispersed ubiquitin aggregates. Furthermore, loss of p97-UBXN1 results in the increase in Huntingtin polyQ aggregates both in mammalian cells as well as in a C.elegans model of Huntington’s Disease. Together our work identifies evolutionarily conserved roles for p97 and its adaptor UBXN1 in the disposal of protein aggregates.

scholarly journals Proteasomal regulation of mammalian SPT16 in controlling transcription.

2021 ◽  
Author(s):  
Amala Kaja ◽  
Abhinav Adhikari ◽  
Saswati Karmakar ◽  
Wanwei Zhang ◽  
Gerson Rothschild ◽  
...  
Keyword(s):  
Proteolytic Activity ◽  
Kidney Cancer ◽  
Ubiquitin Proteasome System ◽  
Proteasomal Degradation ◽  
C2c12 Cells ◽  
Hek293 Cells ◽  
Human Embryonic Kidney ◽  
Physiological Relevance ◽  
Evolutionarily Conserved ◽  
Ubiquitin Proteasome

FACT (Facilitates Chromatin Transcription), an essential and evolutionarily conserved heterodimer from yeast to humans, controls transcription and is found to be upregulated in various cancers. However, the basis for such upregulation is not clearly understood. Our recent results deciphering a new ubiquitin-proteasome system regulation of the FACT subunit, SPT16, in orchestrating transcription in yeast hint to the involvement of the proteasome in controlling FACT in humans with a link to cancer. To test this, we carried out experiments in human embryonic kidney (HEK293) cells, which revealed that human SPT16 undergoes ubiquitylation and its abundance is increased following inhibition of the proteolytic activity of the proteasome, thus implying proteasomal regulation of human SPT16. Further, we find that increased abundance/expression of SPT16 in HEK293 cells alters the transcription of genes including ones associated with cancer, and proteasomal degradation of SPT16 is impaired in kidney cancer (Caki-2) cells to upregulate SPT16. Like human SPT16, murine SPT16 in C2C12 cells also undergoes ubiquitylation and proteasomal degradation to regulate transcription. Collectively, our results reveal a proteasomal regulation of mammalian SPT16 with physiological relevance in controlling transcription, and implicate such proteasomal control in the upregulation of SPT16 in cancer.

Ubiquitin–Proteasome System Regulation of an Evolutionarily Conserved RNA Polymerase II-Associated Factor 1 Involved in Pancreatic Oncogenesis

Biochemistry ◽  
2017 ◽  
Vol 56 (46) ◽  
pp. 6083-6086 ◽  
Author(s):  
Jannatul Ferdoush ◽  
Saswati Karmakar ◽  
Priyanka Barman ◽  
Amala Kaja ◽  
Bhawana Uprety ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ubiquitin Proteasome System ◽  
Associated Factor ◽  
Evolutionarily Conserved ◽  
Ubiquitin Proteasome

Abstract P043: The COP9 Signalosome Regulates Autophagy

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Huabo Su ◽  
Faqian Li ◽  
Mark J Ranek ◽  
Ning Wei ◽  
Xuejun (XJ) Wang
Keyword(s):  
Premature Death ◽  
Ubiquitin Proteasome System ◽  
Reciprocal Relationship ◽  
Cop9 Signalosome ◽  
Autophagic Flux ◽  
Selective Autophagy ◽  
Protein Levels ◽  
Evolutionarily Conserved ◽  
Ubiquitin Proteasome ◽  
Lc3 Puncta

By indiscriminately degrading portions of cytoplasm for self-supply of nutrients, non-selective autophagy helps the cell to survive starvation. Selective autophagy, however, removes defective/surplus organelles and protein aggregates, thereby playing an important role in quality control in the cell. A utophagy is involved in the pathophysiology of a variety of disease, including common forms of heart disease. Mechanisms regulating autophagy, especially selective autophagy, remain poorly understood. The COP9 signalosome (CSN) is an evolutionarily conserved protein complex consisting of 8 subunits (CSN1 through CSN8). CSN was purported to regulate ubiquitin-proteasome system (UPS) mediated proteolysis. We recently reported UPS malfunction and the accumulation of ubiquitin positive aggregates in the cardiomyocytes of mice with perinatal cardiomyocyte-restricted Csn8 knockout (CR-Csn8KO), which displayed massive cardiomyocyte necrosis, congestive heart failure, and premature death. Here we report that Csn8/CSN is required for the removal of autophagosomes in cardiomyocytes, an exciting discovery that has not been reported in any types of cells. CR-Csn8KO mouse hearts show marked increases in LC3-II, indicative of increased autophagosomes. The increase in LC-II is accompanied by a significant increase in p62 protein levels, which is evident as early as 1 week of age, long before the accumulation of a surrogate UPS substrate becomes discernible. The increase in autophagosomes is confirmed by probing with a transgenic GFP-LC3 and by electron microscopy. Autophagic flux assessments reveal that the removal of autophagosomes in cardiomyocytes is impaired by Csn8 deficiency and the defective fusion between autophagosomes and lysosomes may be responsible. Rab7 transcript and protein levels in the heart are significantly decreased by Csn8 deficiency. Confocal microscopy reveals a striking reciprocal relationship between increases in GFP-LC3 puncta and the decreased Rab7 expression. Rab7 knockdown impairs the removal of autophagosomes in cultured cardiomyocytes. Hence, Csn8/CSN is a central regulator in not only the UPS but also autophagy. Csn8/CSN supports autophagosome-lysosome fusion likely by stimulating Rab7 expression.

scholarly journals Proteasome homeostasis is essential for a robust cauliflower mosaic virus infection

2021 ◽  
Author(s):  
Aayushi Shukla ◽  
Suayib Ustun ◽  
Anders Hafrén
Keyword(s):  
Mosaic Virus ◽  
Viral Infections ◽  
Plant Immunity ◽  
Ubiquitin Proteasome System ◽  
Cauliflower Mosaic Virus ◽  
Fine Tuning ◽  
Cellular Processes ◽  
Ubiquitin Proteasome ◽  
Specific Virus ◽  
And Shifts

SummaryThe ubiquitin-proteasome system (UPS) is essential for the maintenance and shifts in protein homeostasis, and thereby forms a founding pillar in virtually all cellular processes including plant immunity and viral infections. According to its importance in fine-tuning the complex plant immune response, proteasomal defects result in divergent outcomes including both resistance and susceptibility phenotypes in response to viruses. The final outcome will largely depend on the specific virus and its specific co-adaptation with the UPS as well as the immune system. Here, we show that cauliflower mosaic virus (CaMV) relies on the proteasome for robust infection. The proteasome system is induced during infection via SA and supports systemic accumulation of the virus as well as plant growth performance during infection. This establishes the UPS as a win-win pathway for the plant and the virus, and together with our demonstration of a proteasome-suppressing viral effector, the intimacy between the proteasome and CaMV is fortified.

scholarly journals An mRNA Capping Enzyme Targets FACT to the Active Gene To Enhance the Engagement of RNA Polymerase II into Transcriptional Elongation

2017 ◽  
Vol 37 (13) ◽  
Author(s):  
Rwik Sen ◽  
Amala Kaja ◽  
Jannatul Ferdoush ◽  
Shweta Lahudkar ◽  
Priyanka Barman ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcriptional Elongation ◽  
Regulatory Pathway ◽  
Pol Ii ◽  
Content Type ◽  
Active Gene ◽  
Mrna Capping ◽  
Capping Enzyme ◽  
Pol Ii Pausing

ABSTRACT We have recently demonstrated that an mRNA capping enzyme, Cet1, impairs promoter-proximal accumulation/pausing of RNA polymerase II (Pol II) independently of its capping activity in Saccharomyces cerevisiae to control transcription. However, it is still unknown how Pol II pausing is regulated by Cet1. Here, we show that Cet1's N-terminal domain (NTD) promotes the recruitment of FACT (facilitates chromatin transcription that enhances the engagement of Pol II into transcriptional elongation) to the coding sequence of an active gene, ADH1, independently of mRNA-capping activity. Absence of Cet1's NTD decreases FACT targeting to ADH1 and consequently reduces the engagement of Pol II in transcriptional elongation, leading to promoter-proximal accumulation of Pol II. Similar results were also observed at other genes. Consistently, Cet1 interacts with FACT. Collectively, our results support the notion that Cet1's NTD promotes FACT targeting to the active gene independently of mRNA-capping activity in facilitating Pol II's engagement in transcriptional elongation, thus deciphering a novel regulatory pathway of gene expression.

The ubiquitin–proteasome system and skeletal muscle wasting

2005 ◽  
Vol 41 ◽  
pp. 173-186 ◽  
Author(s):  
Didier Attaix ◽  
Sophie Ventadour ◽  
Audrey Codran ◽  
Daniel Béchet ◽  
Daniel Taillandier ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Wasting ◽  
Proteolytic Enzymes ◽  
Cathepsin L ◽  
Ubiquitin Proteasome System ◽  
Complete Breakdown ◽  
Skeletal Muscle Proteins ◽  
Ubiquitin Proteasome ◽  
Tripeptidyl Peptidase Ii ◽  
F Box Protein

The ubiquitin–proteasome system (UPS) is believed to degrade the major contractile skeletal muscle proteins and plays a major role in muscle wasting. Different and multiple events in the ubiquitination, deubiquitination and proteolytic machineries are responsible for the activation of the system and subsequent muscle wasting. However, other proteolytic enzymes act upstream (possibly m-calpain, cathepsin L, and/or caspase 3) and downstream (tripeptidyl-peptidase II and aminopeptidases) of the UPS, for the complete breakdown of the myofibrillar proteins into free amino acids. Recent studies have identified a few critical proteins that seem necessary for muscle wasting {i.e. the MAFbx (muscle atrophy F-box protein, also called atrogin-1) and MuRF-1 [muscle-specific RING (really interesting new gene) finger 1] ubiquitin–protein ligases}. The characterization of their signalling pathways is leading to new pharmacological approaches that can be useful to block or partially prevent muscle wasting in human patients.

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