1
|
Quaye JA, Ball J, Gadda G. Kinetic solvent viscosity effects uncover an internal isomerization of the enzyme-substrate complex in Pseudomonas aeruginosa PAO1 NADH:Quinone oxidoreductase. Arch Biochem Biophys 2022; 727:109342. [PMID: 35777523 DOI: 10.1016/j.abb.2022.109342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 11/02/2022]
Abstract
NAD(P)H:quinone oxidoreductases (NQOs) play an essential protective role as antioxidants in the detoxification of quinones in both Prokaryotes and Eukaryotes. NQO from Pseudomonas aeruginosa PAO1 uses FMN to catalyze the two-electron reduction of various quinones with NADH. In this study, steady-state kinetics, kinetic solvent viscosity effects, and rapid reaction kinetics were used to determine which kinetic steps control the overall turnover of the enzyme with benzoquinone or juglone. The rate constant for flavin reduction (kred) at pH 6.0 was 12.9 ± 0.3 s-1, and the Kd for NADH was at least an order of magnitude lower than 90 μM. With benzoquinone, the kcat value was 11.7 ± 0.3 s-1, consistent with flavin reduction being almost entirely rate-limiting for overall turnover. With juglone, a kcat value of 10.0 ± 0.5 s-1 was recorded. The normalized plot of the relative solvent viscosity effects on the kcat values established that hydride transfer from NADH to the FMN and quinol product release, with a calculated rate constant (kP-rel) of 52 s-1, are partially rate-limiting for the overall turnover of NQO. Kinetic solvent viscosity effects with glucose or sucrose revealed a hyperbolic dependence on the kcat and kcat/Km values with benzoquinone or juglone, respectively, consistent with the presence of a solvent-sensitive internal isomerization of the enzyme-substrate complex (ES). The data demonstrate opposing effects of benzoquinone and juglone on the equilibrium of the NQO ES isomerization with glucose or sucrose. Thus, our study demonstrates how quinol substrate properties alter the equilibrium of NQO ES isomerization.
Collapse
Affiliation(s)
- Joanna A Quaye
- Department of Chemistry, Georgia State University, P.O. Box 3965, Atlanta, GA, 30302, USA
| | - Jacob Ball
- Department of Chemistry, Georgia State University, P.O. Box 3965, Atlanta, GA, 30302, USA
| | - Giovanni Gadda
- Department of Chemistry, Georgia State University, P.O. Box 3965, Atlanta, GA, 30302, USA; Department of Biology, Georgia State University, Atlanta, GA, 30302, USA; Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, 30302, USA.
| |
Collapse
|
2
|
Darling AL, Uversky VN. Intrinsic Disorder and Posttranslational Modifications: The Darker Side of the Biological Dark Matter. Front Genet 2018; 9:158. [PMID: 29780404 PMCID: PMC5945825 DOI: 10.3389/fgene.2018.00158] [Citation(s) in RCA: 154] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 04/17/2018] [Indexed: 01/05/2023] Open
Abstract
Intrinsically disordered proteins (IDPs) and intrinsically disordered protein regions (IDPRs) are functional proteins and domains that devoid stable secondary and/or tertiary structure. IDPs/IDPRs are abundantly present in various proteomes, where they are involved in regulation, signaling, and control, thereby serving as crucial regulators of various cellular processes. Various mechanisms are utilized to tightly regulate and modulate biological functions, structural properties, cellular levels, and localization of these important controllers. Among these regulatory mechanisms are precisely controlled degradation and different posttranslational modifications (PTMs). Many normal cellular processes are associated with the presence of the right amounts of precisely activated IDPs at right places and in right time. However, wrecked regulation of IDPs/IDPRs might be associated with various human maladies, ranging from cancer and neurodegeneration to cardiovascular disease and diabetes. Pathogenic transformations of IDPs/IDPRs are often triggered by altered PTMs. This review considers some of the aspects of IDPs/IDPRs and their normal and aberrant regulation by PTMs.
Collapse
Affiliation(s)
- April L Darling
- Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Vladimir N Uversky
- Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, United States.,Laboratory of New Methods in Biology, Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Russia
| |
Collapse
|
3
|
Prolyl isomerase PIN1 regulates the stability, transcriptional activity and oncogenic potential of BRD4. Oncogene 2017; 36:5177-5188. [PMID: 28481868 PMCID: PMC5589477 DOI: 10.1038/onc.2017.137] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 02/23/2017] [Accepted: 04/04/2017] [Indexed: 12/13/2022]
Abstract
BRD4 has emerged as an important factor in tumorigenesis by promoting the transcription of genes involved in cancer development. However, how BRD4 is regulated in cancer cells remains largely unknown. Here, we report that the stability and functions of BRD4 are positively regulated by prolyl-isomerase PIN1 in gastric cancer cells. PIN1 directly binds to phosphorylated threonine (T) 204 of BRD4 as revealed by peptide binding and crystallographic studies and enhances BRD4’s stability by inhibiting its ubiquitination. PIN1 also catalyses the isomerization of proline 205 of BRD4 and induces its conformational change, which promotes its interaction with CDK9 and increases BRD4’s transcriptional activity. Substitution of BRD4 with PIN1 binding-defective BRD4-T204A mutant in gastric cancer cells reduces BRD4’s stability, attenuates BRD4-mediated gene expression by impairing its interaction with CDK9, and suppresses gastric cancer cell proliferation, migration and invasion, and tumor formation. Our results identify BRD4 as a new target of PIN1 and suggest that interfering with their interaction could be a potential therapeutic approach for cancer treatment.
Collapse
|
4
|
Lu L, Fan D, Hu CW, Worth M, Ma ZX, Jiang J. Distributive O-GlcNAcylation on the Highly Repetitive C-Terminal Domain of RNA Polymerase II. Biochemistry 2016; 55:1149-58. [PMID: 26807597 DOI: 10.1021/acs.biochem.5b01280] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
O-GlcNAcylation is a nutrient-responsive glycosylation that plays a pivotal role in transcriptional regulation. Human RNA polymerase II (Pol II) is extensively modified by O-linked N-acetylglucosamine (O-GlcNAc) on its unique C-terminal domain (CTD), which consists of 52 heptad repeats. One approach to understanding the function of glycosylated Pol II is to determine the mechanism of dynamic O-GlcNAcylation on the CTD. Here, we discovered that the Pol II CTD can be extensively O-GlcNAcylated in vitro and in cells. Efficient glycosylation requires a minimum of 20 heptad repeats of the CTD and more than half of the N-terminal domain of O-GlcNAc transferase (OGT). Under conditions of saturated sugar donor, we monitored the attachment of more than 20 residues of O-GlcNAc to the full-length CTD. Surprisingly, glycosylation on the periodic CTD follows a distributive mechanism, resulting in highly heterogeneous glycoforms. Our data suggest that initial O-GlcNAcylation can take place either on the proximal or on the distal region of the CTD, and subsequent glycosylation occurs similarly over the entire CTD with nonuniform distributions. Moreover, removal of O-GlcNAc from glycosylated CTD is also distributive and is independent of O-GlcNAcylation level. Our results suggest that O-GlcNAc cycling enzymes can employ a similar mechanism to react with other protein substrates on multiple sites. Distributive O-GlcNAcylation on Pol II provides another regulatory mechanism of transcription in response to fluctuating cellular conditions.
Collapse
Affiliation(s)
- Lei Lu
- Pharmaceutical Sciences Division, School of Pharmacy, and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| | - Dacheng Fan
- Pharmaceutical Sciences Division, School of Pharmacy, and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| | - Chia-Wei Hu
- Pharmaceutical Sciences Division, School of Pharmacy, and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| | - Matthew Worth
- Pharmaceutical Sciences Division, School of Pharmacy, and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| | - Zhi-Xiong Ma
- Pharmaceutical Sciences Division, School of Pharmacy, and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| | - Jiaoyang Jiang
- Pharmaceutical Sciences Division, School of Pharmacy, and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States
| |
Collapse
|
5
|
Mayfield JE, Burkholder NT, Zhang YJ. Dephosphorylating eukaryotic RNA polymerase II. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:372-87. [PMID: 26779935 DOI: 10.1016/j.bbapap.2016.01.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 01/11/2016] [Accepted: 01/14/2016] [Indexed: 12/20/2022]
Abstract
The phosphorylation state of the C-terminal domain of RNA polymerase II is required for the temporal and spatial recruitment of various factors that mediate transcription and RNA processing throughout the transcriptional cycle. Therefore, changes in CTD phosphorylation by site-specific kinases/phosphatases are critical for the accurate transmission of information during transcription. Unlike kinases, CTD phosphatases have been traditionally neglected as they are thought to act as passive negative regulators that remove all phosphate marks at the conclusion of transcription. This over-simplified view has been disputed in recent years and new data assert the active and regulatory role phosphatases play in transcription. We now know that CTD phosphatases ensure the proper transition between different stages of transcription, balance the distribution of phosphorylation for accurate termination and re-initiation, and prevent inappropriate expression of certain genes. In this review, we focus on the specific roles of CTD phosphatases in regulating transcription. In particular, we emphasize how specificity and timing of dephosphorylation are achieved for these phosphatases and consider the various regulatory factors that affect these dynamics.
Collapse
Affiliation(s)
- Joshua E Mayfield
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Nathaniel T Burkholder
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Yan Jessie Zhang
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
| |
Collapse
|
6
|
Post-Translational Modifications and RNA-Binding Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 907:297-317. [PMID: 27256391 DOI: 10.1007/978-3-319-29073-7_12] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
RNA-binding proteins affect cellular metabolic programs through development and in response to cellular stimuli. Though much work has been done to elucidate the roles of a handful of RNA-binding proteins and their effect on RNA metabolism, the progress of studies to understand the effects of post-translational modifications of this class of proteins is far from complete. This chapter summarizes the work that has been done to identify the consequence of post-translational modifications to some RNA-binding proteins. The effects of these modifications have been shown to increase the panoply of functions that a given RNA-binding protein can assume. We will survey the experimental methods that are used to identify the presence of several protein modifications and methods that attempt to discern the consequence of these modifications.
Collapse
|
7
|
Abstract
The RNA polymerase II transcription cycle is often divided into three major stages: initiation, elongation, and termination. Research over the last decade has blurred these divisions and emphasized the tightly regulated transitions that occur as RNA polymerase II synthesizes a transcript from start to finish. Transcription termination, the process that marks the end of transcription elongation, is regulated by proteins that interact with the polymerase, nascent transcript, and/or chromatin template. The failure to terminate transcription can cause accumulation of aberrant transcripts and interfere with transcription at downstream genes. Here, we review the mechanism, regulation, and physiological impact of a termination pathway that targets small noncoding transcripts produced by RNA polymerase II. We emphasize the Nrd1-Nab3-Sen1 pathway in yeast, in which the process has been extensively studied. The importance of understanding small RNA termination pathways is underscored by the need to control noncoding transcription in eukaryotic genomes.
Collapse
Affiliation(s)
- Karen M Arndt
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260;
| | | |
Collapse
|
8
|
Niklas KJ, Bondos SE, Dunker AK, Newman SA. Rethinking gene regulatory networks in light of alternative splicing, intrinsically disordered protein domains, and post-translational modifications. Front Cell Dev Biol 2015; 3:8. [PMID: 25767796 PMCID: PMC4341551 DOI: 10.3389/fcell.2015.00008] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/26/2015] [Indexed: 11/16/2022] Open
Abstract
Models for genetic regulation and cell fate specification characteristically assume that gene regulatory networks (GRNs) are essentially deterministic and exhibit multiple stable states specifying alternative, but pre-figured cell fates. Mounting evidence shows, however, that most eukaryotic precursor RNAs undergo alternative splicing (AS) and that the majority of transcription factors contain intrinsically disordered protein (IDP) domains whose functionalities are context dependent as well as subject to post-translational modification (PTM). Consequently, many transcription factors do not have fixed cis-acting regulatory targets, and developmental determination by GRNs alone is untenable. Modeling these phenomena requires a multi-scale approach to explain how GRNs operationally interact with the intra- and intercellular environments. Evidence shows that AS, IDP, and PTM complicate gene expression and act synergistically to facilitate and promote time- and cell-specific protein modifications involved in cell signaling and cell fate specification and thereby disrupt a strict deterministic GRN-phenotype mapping. The combined effects of AS, IDP, and PTM give proteomes physiological plasticity, adaptive responsiveness, and developmental versatility without inefficiently expanding genome size. They also help us understand how protein functionalities can undergo major evolutionary changes by buffering mutational consequences.
Collapse
Affiliation(s)
- Karl J Niklas
- Plant Biology Section, School of Integrative Plant Science, Cornell University Ithaca, NY, USA
| | - Sarah E Bondos
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College Station, TX, USA
| | - A Keith Dunker
- Center for Computational Biology and Bioinformatics, School of Medicine, Indiana University Indianapolis, IN, USA
| | - Stuart A Newman
- Department of Cell Biology and Anatomy, New York Medical College Valhalla, NY, USA
| |
Collapse
|