1
|
Reynolds MF. New insights into the signal transduction mechanism of O 2-sensing FixL and other biological heme-based sensor proteins. J Inorg Biochem 2024; 259:112642. [PMID: 38908215 DOI: 10.1016/j.jinorgbio.2024.112642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 05/24/2024] [Accepted: 06/13/2024] [Indexed: 06/24/2024]
Abstract
Recent structural and biophysical studies of O2-sensing FixL, NO-sensing soluble guanylate cyclase, and other biological heme-based sensing proteins have begun to reveal the details of their molecular mechanisms and shed light on how nature regulates important biological processes such as nitrogen fixation, blood pressure, neurotransmission, photosynthesis and circadian rhythm. The O2-sensing FixL protein from S. meliloti, the eukaryotic NO-sensing protein sGC, and the CO-sensing CooA protein from R. rubrum transmit their biological signals through gas-binding to the heme domain of these proteins, which inhibits or activates the regulatory, enzymatic domain. These proteins appear to propagate their signal by specific structural changes in the heme sensor domain initiated by the appropriate gas binding to the heme, which is then propagated through a coiled-coil linker or other domain to the regulatory, enzymatic domain that sends out the biological signal. The current understanding of the signal transduction mechanisms of O2-sensing FixL, NO-sensing sGC, CO-sensing CooA and other biological heme-based gas sensing proteins and their mechanistic themes are discussed, with recommendations for future work to further understand this rapidly growing area of biological heme-based gas sensors.
Collapse
Affiliation(s)
- Mark F Reynolds
- Department of Chemistry and Biochemistry, Saint Joseph's University, 5600 City Avenue, Philadelphia, PA 19131, United States of America.
| |
Collapse
|
2
|
Ali HS, de Visser SP. QM/MM Study Into the Mechanism of Oxidative C=C Double Bond Cleavage by Lignostilbene-α,β-Dioxygenase. Chemistry 2024; 30:e202304172. [PMID: 38373118 DOI: 10.1002/chem.202304172] [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: 12/14/2023] [Revised: 01/29/2024] [Accepted: 02/19/2024] [Indexed: 02/21/2024]
Abstract
The enzymatic biosynthesis of fragrance molecules from lignin fragments is an important reaction in biotechnology for the sustainable production of fine chemicals. In this work we investigated the biosynthesis of vanillin from lignostilbene by a nonheme iron dioxygenase using QM/MM and tested several suggested proposals via either an epoxide or dioxetane intermediate. Binding of dioxygen to the active site of the protein results in the formation of an iron(II)-superoxo species with lignostilbene cation radical. The dioxygenase mechanism starts with electrophilic attack of the terminal oxygen atom of the superoxo group on the central C=C bond of lignostilbene, and the second-coordination sphere effects in the substrate binding pocket guide the reaction towards dioxetane formation. The computed mechanism is rationalized with thermochemical cycles and valence bond schemes that explain the electron transfer processes during the reaction mechanism. Particularly, the polarity of the protein and the local electric field and dipole moments enable a facile electron transfer and an exergonic dioxetane formation pathway.
Collapse
Affiliation(s)
- Hafiz Saqib Ali
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| |
Collapse
|
3
|
Lindahl PA. Iron Homeostatic Regulation in Saccharomyces cerevisiae: Introduction to a Computational Modeling Method. Methods Mol Biol 2024; 2839:3-29. [PMID: 39008245 DOI: 10.1007/978-1-0716-4043-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Over the past 30 years, much has been learned regarding iron homeostatic regulation in budding yeast, S. cerevisiae, including the identity of many of the proteins and molecular-level regulatory mechanisms involved. Most advances have involved inferring such mechanisms based on the analysis of iron-dysregulation phenotypes arising in various genetic mutant strains. Still lacking is a cellular- or system-level understanding of iron homeostasis. These experimental advances are summarized in this review, and a method for developing cellular-level regulatory mechanisms in yeast is presented. The method employs the results of Mössbauer spectroscopy of whole cells and organelles, iron quantification of the same, and ordinary differential equation-based mathematical models. Current models are simplistic when compared to the complexity of iron homeostasis in real cells, yet they hold promise as a useful, perhaps even required, complement to the popular genetics-based approach. The fundamental problem in comprehending cellular regulatory mechanisms is that, given the complexities involved, different molecular-level mechanisms can often give rise to virtually indistinguishable cellular phenotypes. Mathematical models cannot eliminate this problem, but they can minimize it.
Collapse
Affiliation(s)
- Paul A Lindahl
- Departments of Chemistry and of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA.
| |
Collapse
|
4
|
Zhou Y, Chen J, Pu W, Cai N, Che B, Yang J, Wang M, Zhong S, Zuo X, Wang D, Wang Y, Zheng P, Sun J. Development of a growth-coupled selection platform for directed evolution of heme biosynthetic enzymes in Corynebacterium glutamicum. Front Bioeng Biotechnol 2023; 11:1236118. [PMID: 37654705 PMCID: PMC10465345 DOI: 10.3389/fbioe.2023.1236118] [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: 06/07/2023] [Accepted: 08/04/2023] [Indexed: 09/02/2023] Open
Abstract
Heme is an important tetrapyrrole compound, and has been widely applied in food and medicine industries. Although microbial production of heme has been developed with metabolic engineering strategies during the past 20 years, the production levels are relatively low due to the multistep enzymatic processes and complicated regulatory mechanisms of microbes. Previous studies mainly adopted the strategies of strengthening precursor supply and product transportation to engineer microbes for improving heme biosynthesis. Few studies focused on the engineering and screening of efficient enzymes involved in heme biosynthesis. Herein, a growth-coupled, high-throughput selection platform based on the detoxification of Zinc-protoporphyrin IX (an analogue of heme) was developed and applied to directed evolution of coproporphyrin ferrochelatase, catalyzing the insertion of metal ions into porphyrin ring to generate heme or other tetrapyrrole compounds. A mutant with 3.03-fold increase in k cat/K M was selected. Finally, growth-coupled directed evolution of another three key enzymes involved in heme biosynthesis was tested by using this selection platform. The growth-coupled selection platform developed here can be a simple and effective strategy for directed evolution of the enzymes involved in the biosynthesis of heme or other tetrapyrrole compounds.
Collapse
Affiliation(s)
- Yingyu Zhou
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Jiuzhou Chen
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| | - Wei Pu
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| | - Ningyun Cai
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Bin Che
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| | - Jinxing Yang
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Mengmeng Wang
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Shasha Zhong
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Xingtao Zuo
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Depei Wang
- College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China
| | - Yu Wang
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| | - Ping Zheng
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| | - Jibin Sun
- Key Laboratory of Engineering Biology for Low-Carbon Manufacturing, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- National Technology Innovation Center of Synthetic Biology, Tianjin, China
| |
Collapse
|
5
|
Freeman SL, Oliveira ASF, Gallio AE, Rosa A, Simitakou MK, Arthur CJ, Mulholland AJ, Cherepanov P, Raven EL. Heme binding to the SARS-CoV-2 spike glycoprotein. J Biol Chem 2023; 299:105014. [PMID: 37414149 PMCID: PMC10416065 DOI: 10.1016/j.jbc.2023.105014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/12/2023] [Accepted: 07/01/2023] [Indexed: 07/08/2023] Open
Abstract
The target for humoral immunity, SARS-CoV-2 spike glycoprotein, has become the focus of vaccine research and development. Previous work demonstrated that the N-terminal domain (NTD) of SARS-CoV-2 spike binds biliverdin-a product of heme catabolism-causing a strong allosteric effect on the activity of a subset of neutralizing antibodies. Herein, we show that the spike glycoprotein is also able to bind heme (KD = 0.5 ± 0.2 μM). Molecular modeling indicated that the heme group fits well within the same pocket on the SARS-CoV-2 spike NTD. Lined by aromatic and hydrophobic residues (W104, V126, I129, F192, F194, I203, and L226), the pocket provides a suitable environment to stabilize the hydrophobic heme. Mutagenesis of N121 has a substantive effect on heme binding (KD = 3000 ± 220 μM), confirming the pocket as a major heme binding location of the viral glycoprotein. Coupled oxidation experiments in the presence of ascorbate indicated that the SARS-CoV-2 glycoprotein can catalyze the slow conversion of heme to biliverdin. The heme trapping and oxidation activities of the spike may allow the virus to reduce levels of free heme during infection to facilitate evasion of the adaptive and innate immunity.
Collapse
Affiliation(s)
- Samuel L Freeman
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, United Kingdom
| | - A Sofia F Oliveira
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, United Kingdom
| | - Andrea E Gallio
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, United Kingdom
| | - Annachiara Rosa
- Chromatin Structure and Mobile DNA Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Maria K Simitakou
- Chromatin Structure and Mobile DNA Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Christopher J Arthur
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, United Kingdom
| | - Adrian J Mulholland
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, United Kingdom
| | - Peter Cherepanov
- Chromatin Structure and Mobile DNA Laboratory, The Francis Crick Institute, London, United Kingdom; Department of Infectious Disease, St-Mary's Campus, Imperial College London, United Kingdom.
| | - Emma L Raven
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, United Kingdom.
| |
Collapse
|
6
|
Wang M, Wang Y, Wang M, Liu M, Cheng A. Heme acquisition and tolerance in Gram-positive model bacteria: An orchestrated balance. Heliyon 2023; 9:e18233. [PMID: 37501967 PMCID: PMC10368836 DOI: 10.1016/j.heliyon.2023.e18233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/26/2023] [Accepted: 07/12/2023] [Indexed: 07/29/2023] Open
Abstract
As a nutrient, heme is important for various cellular processes of organism. Bacteria can obtain heme via heme biosynthesis or/and uptake of exogenous heme from the host. On the other side, absorption of excess heme is cytotoxic to bacteria. Thus, bacteria have developed systems to relieve heme toxicity and contribute to the maintenance of heme homeostasis. In the past decades, the mechanisms underlying heme acquisition and tolerance have been well studied in Gram-positive model bacteria, such as Staphylococcus, Streptococcus and other Gram-positive bacteria. Here, we review the elaborate mechanisms by which these bacteria acquire heme and resist heme toxicity. Since both the heme utilization system and the heme tolerance system contribute to bacterial virulence, this review is not only helpful for a comprehensive understanding of the heme homeostasis mechanism in Gram-positive bacteria but also provides a theoretical basis for the development of antimicrobial agents.
Collapse
Affiliation(s)
- Mengying Wang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu 611130, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu 611130, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu 611130, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
| | - Yuwei Wang
- Mianyang Academy of Agricultural Sciences, Institute of Livestock Research, Mianyang 621023, China
| | - Mingshu Wang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu 611130, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu 611130, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu 611130, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
| | - Mafeng Liu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu 611130, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu 611130, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu 611130, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
| | - Anchun Cheng
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu 611130, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu 611130, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu 611130, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
| |
Collapse
|
7
|
Abstract
Ferric heme b (= ferric protoporphyrin IX = hemin) is an important prosthetic group of different types of enzymes, including the intensively investigated and widely applied horseradish peroxidase (HRP). In HRP, hemin is present in monomeric form in a hydrophobic pocket containing among other amino acid side chains the two imidazoyl groups of His170 and His42. Both amino acids are important for the peroxidase activity of HRP as an axial ligand of hemin (proximal His170) and as an acid/base catalyst (distal His42). A key feature of the peroxidase mechanism of HRP is the initial formation of compound I under heterolytic cleavage of added hydrogen peroxide as a terminal oxidant. Investigations of free hemin dispersed in aqueous solution showed that different types of hemin dimers can form, depending on the experimental conditions, possibly resulting in hemin crystallization. Although it has been recognized already in the 1970s that hemin aggregation can be prevented in aqueous solution by using micelle-forming amphiphiles, it remains a challenge to prepare hemin-containing micellar and vesicular systems with peroxidase-like activities. Such systems are of interest as cheap HRP-mimicking catalysts for analytical and synthetic applications. Some of the key concepts on which research in this fascinating and interdisciplinary field is based are summarized, along with major accomplishments and possible directions for further improvement. A systematic analysis of the physico-chemical properties of hemin in aqueous micellar solutions and vesicular dispersions must be combined with a reliable evaluation of its catalytic activity. Future studies should show how well the molecular complexity around hemin in HRP can be mimicked by using micelles or vesicles. Because of the importance of heme b in virtually all biological systems and the fact that porphyrins and hemes can be obtained under potentially prebiotic conditions, ideas exist about the possible role of heme-containing micellar and vesicular systems in prebiotic times.
Collapse
|
8
|
Vávra J, Sergunin A, Jeřábek P, Shimizu T, Martínková M. Signal transduction mechanisms in heme-based globin-coupled oxygen sensors with a focus on a histidine kinase ( AfGcHK) and a diguanylate cyclase (YddV or EcDosC). Biol Chem 2022; 403:1031-1042. [PMID: 36165459 DOI: 10.1515/hsz-2022-0185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 09/08/2022] [Indexed: 01/19/2023]
Abstract
Heme is a vital cofactor of proteins with roles in oxygen transport (e.g. hemoglobin), storage (e.g. myoglobin), and activation (e.g. P450) as well as electron transfer (e.g. cytochromes) and many other functions. However, its structural and functional role in oxygen sensing proteins differs markedly from that in most other enzymes, where it serves as a catalytic or functional center. This minireview discusses the mechanism of signal transduction in two heme-based oxygen sensors: the histidine kinase AfGcHK and the diguanylate cyclase YddV (EcDosC), both of which feature a heme-binding domain containing a globin fold resembling that of hemoglobin and myoglobin.
Collapse
Affiliation(s)
- Jakub Vávra
- Department of Biochemistry, Faculty of Science, Charles University, Prague 2, 128 43 Czech Republic
| | - Artur Sergunin
- Department of Biochemistry, Faculty of Science, Charles University, Prague 2, 128 43 Czech Republic
| | - Petr Jeřábek
- Department of Biochemistry, Faculty of Science, Charles University, Prague 2, 128 43 Czech Republic
| | - Toru Shimizu
- Department of Biochemistry, Faculty of Science, Charles University, Prague 2, 128 43 Czech Republic
| | - Markéta Martínková
- Department of Biochemistry, Faculty of Science, Charles University, Prague 2, 128 43 Czech Republic
| |
Collapse
|
9
|
Krüger A, Frunzke J. A pseudokinase version of the histidine kinase ChrS promotes high heme tolerance of Corynebacterium glutamicum. Front Microbiol 2022; 13:997448. [PMID: 36160252 PMCID: PMC9491836 DOI: 10.3389/fmicb.2022.997448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 08/18/2022] [Indexed: 11/21/2022] Open
Abstract
Heme is an essential cofactor for almost all living cells by acting as prosthetic group for various proteins or serving as alternative iron source. However, elevated levels are highly toxic for cells. Several corynebacterial species employ two paralogous, heme-responsive two-component systems (TCS), ChrSA and HrrSA, to cope with heme stress and to maintain intracellular heme homeostasis. Significant cross-talk at the level of phosphorylation between these systems was previously demonstrated. In this study, we have performed a laboratory evolution experiment to adapt Corynebacterium glutamicum to increasing heme levels. Isolated strains showed a highly increased tolerance to heme growing at concentrations of up to 100 μM. The strain featuring the highest heme tolerance harbored a frameshift mutation in the catalytical and ATPase-domain (CA-domain) of the chrS gene, converting it into a catalytically-inactive pseudokinase (ChrS_CA-fs). Reintroduction of the respective mutation in the parental C. glutamicum strain confirmed high heme tolerance and showed a drastic upregulation of hrtBA encoding a heme export system, conserved in Firmicutes and Actinobacteria. The strain encoding the ChrS pseudokinase variant showed significantly higher heme tolerance than a strain lacking chrS. Mutational analysis revealed that induction of hrtBA in the evolved strain is solely mediated via the cross-phosphorylation of the response regulator (RR) ChrA by the kinase HrrS and BACTH assays revealed the formation of heterodimers between HrrS and ChrS. Overall, our results emphasize an important role of the ChrS pseudokinase in high heme tolerance of the evolved C. glutamicum and demonstrate the promiscuity in heme-dependent signaling of the paralogous two-component systems facilitating fast adaptation to changing environmental conditions.
Collapse
|
10
|
Liao R, Bresnick EH. Heme as a differentiation-regulatory transcriptional cofactor. Int J Hematol 2022; 116:174-181. [PMID: 35776402 PMCID: PMC10170499 DOI: 10.1007/s12185-022-03404-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/03/2022] [Accepted: 06/07/2022] [Indexed: 01/10/2023]
Abstract
The hematopoietic transcription factor GATA1 induces heme accumulation during erythropoiesis by directly activating genes mediating heme biosynthesis. In addition to its canonical functions as a hemoglobin prosthetic group and enzyme cofactor, heme regulates gene expression in erythroid cells both transcriptionally and post-transcriptionally. Heme binding to the transcriptional repressor BACH1 triggers its proteolytic degradation. In heme-deficient cells, BACH1 accumulates and represses transcription of target genes, including α- and β-like globin genes, preventing the accumulation of cytotoxic free globin chains. A recently described BACH1-independent mechanism of heme-dependent transcriptional regulation is associated with a DNA motif termed heme-regulated motif (HERM), which resides at the majority of loci harboring heme-regulated chromatin accessibility sites. Progress on these problems has led to a paradigm in which cell type-specific transcriptional mechanisms determine the expression of enzymes mediating the synthesis of small molecules, which generate feedback loops, converging upon the transcription factor itself and the genome. This marriage between transcription factors and the small molecules that they control is predicted to be a canonical attribute of regulatory networks governing cell state transitions such as differentiation in the hematopoietic system and more broadly.
Collapse
Affiliation(s)
- Ruiqi Liao
- Wisconsin Blood Cancer Research Institute, Department of Cell and Regenerative Biology, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, 4009 WIMR, Madison, WI, 53705, USA
| | - Emery H Bresnick
- Wisconsin Blood Cancer Research Institute, Department of Cell and Regenerative Biology, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, 4009 WIMR, Madison, WI, 53705, USA.
| |
Collapse
|