1
|
Hopkins MD, Costello IJ, Brandeburg ZC, Slay EL, Zanders LA, Dunn CE, Derewonko CA, Davitt CL, Reeder MA, Prichard K, Chiew B, McCluskey A, Sheaff RJ, Lamar AA. Expansion of a Synthesized Library of N-Benzyl Sulfonamides Derived from an Indole Core to Target Pancreatic Cancer. ChemMedChem 2023; 18:e202300265. [PMID: 37421174 DOI: 10.1002/cmdc.202300265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 07/07/2023] [Accepted: 07/07/2023] [Indexed: 07/09/2023]
Abstract
In an effort to further investigate previously observed activity of indolyl sulfonamides towards pancreatic cancer cell lines, a library of 44 compounds has been synthesized. The biological activity of the compounds has been determined using two different screening assay techniques against 7 pancreatic cancer cell lines and 9 non-pancreatic cancer cell lines. In the first assay, the cytotoxicity of the compounds was evaluated using a traditional (48 hour compound exposure) method. An in silico investigation was conducted to determine if the compounds might be inducing cell death by inhibiting the S100A2-p53 protein-protein interaction. In the second assay, the potential role of the compounds as metabolic inhibitors of ATP production was evaluated using a rapid screening (1-2 hour compound exposure) method. IC50 values of the hit compounds were obtained and four compounds displayed sub-micromolar potency against PANC-1 cells. The investigation has provided several compounds that display selective in vitro activity toward pancreatic cancer that warrant further development.
Collapse
Affiliation(s)
- Megan D Hopkins
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Ian J Costello
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Zachary C Brandeburg
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Emily L Slay
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Levi A Zanders
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Caroline E Dunn
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Carina A Derewonko
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Colin L Davitt
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Madison A Reeder
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Kate Prichard
- Chemistry, School of Environmental & Life Sciences, The University of Newcastle, University Drive, 2308, Callaghan, NSW, Australia
| | - Beatrice Chiew
- Chemistry, School of Environmental & Life Sciences, The University of Newcastle, University Drive, 2308, Callaghan, NSW, Australia
| | - Adam McCluskey
- Chemistry, School of Environmental & Life Sciences, The University of Newcastle, University Drive, 2308, Callaghan, NSW, Australia
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| | - Angus A Lamar
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, 74104, Tulsa, OK, USA
| |
Collapse
|
2
|
Philo JE, Caudle JD, Moussa RN, Kampmeyer PM, Hasin TR, Seo DK, Sheaff RJ, Lamar AA. Synthesis and Biological Evaluation of a Library of Sulfonamide Analogs of Memantine to Target Glioblastoma. ChemMedChem 2023; 18:e202300134. [PMID: 37248422 DOI: 10.1002/cmdc.202300134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/29/2023] [Accepted: 05/29/2023] [Indexed: 05/31/2023]
Abstract
A library of 34 lipophilic sulfonamides based upon the memantine core has been synthesized to identify potential drug candidates to cross the blood-brain barrier and target glioblastoma. The library was screened for in vitro activity against 4 mammalian cell lines, including U-87 (glioblastoma). Additional synthetic variation of the active compounds has validated the importance of specific regions of the pharmacophore, with the sulfonamide functionality and S-aryl unit displaying the most significant impact. In silico investigations suggest the active compounds might target DDR1 or RET proteins. The investigation has resulted in several compounds that warrant further development for lead optimization.
Collapse
Affiliation(s)
- John E Philo
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - Jenna D Caudle
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - Reema N Moussa
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - Patrick M Kampmeyer
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - Tasfia R Hasin
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - David K Seo
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| | - Angus A Lamar
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, OK 74104, USA
| |
Collapse
|
3
|
Hopkins MD, Witt RC, Flusche AME, Philo JE, Ozmer GL, Purser GH, Sheaff RJ, Lamar AA. Synthesis and biological evaluation of N-alkyl sulfonamides derived from polycyclic hydrocarbon scaffolds using a nitrogen-centered radical approach. Org Biomol Chem 2022; 20:6680-6693. [PMID: 35950721 DOI: 10.1039/d2ob01291j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polycyclic hydrocarbons (PH) provide intriguing potential as lipophilic scaffolds within medicinal chemistry, but are currently limited by the availability of synthetic tools for predictable modification of the PH unit. Herein we report the development of new methods for installation of a sulfonamide unit to PH cores. In the first method, a xanthate ester serves as reagent for aminosulfonation using pre-formed imidoiodinane as N-source. An investigation of the reaction mechanism was performed to implicate a process involving a N-centered radical. An additional method for sulfonamide installation is described that involves the use of commercially available reagents and operationally convenient conditions. Using the new synthetic methods, 22 compounds were prepared and screened for biological activity against 6 mammalian cell lines along with Gram-positive and Gram-negative bacterial strains. Results of the viability assays have identified compounds that exhibit higher potency than other known anticancer agents such as indisulam and ABT-751. Additionally, the physicochemical and drug-likeness properties of the synthesized compounds have been determined experimentally and using in silico predictive tools. The initial exploration into sulfonamide insertion into PH cores has resulted in a number of compounds that warrant further development to produce molecules with therapeutic value.
Collapse
Affiliation(s)
- Megan D Hopkins
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - Ryan C Witt
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - Ann Marie E Flusche
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - John E Philo
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - Garett L Ozmer
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - Gordon H Purser
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| | - Angus A Lamar
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma, 74104, USA.
| |
Collapse
|
4
|
Abebe F, Hopkins MD, Vodnala SN, Sheaff RJ, Lamar AA. Development of a Rapid In Vitro Screening Assay Using Metabolic Inhibitors to Detect Highly Selective Anticancer Agents. ACS Omega 2021; 6:18333-18343. [PMID: 34308064 PMCID: PMC8296616 DOI: 10.1021/acsomega.1c02203] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/23/2021] [Indexed: 05/06/2023]
Abstract
Traditional long exposure (24-72 h) cell viability assays for identification of potential drug compounds can fail to identify compounds that are: (a) biologically active but not toxic and (b) inactive without the addition of a synergistic additive. Herein, we report the development of a rapid (1-2 h) compound screening technique using a commercially available cell viability kit (CellTiter-Glo) that has led to the detection of compounds that were not identified as active agents using traditional cytotoxicity screening methods. These compounds, in combination with metabolic inhibitor 2-deoxyglucose, display selectivity toward a pancreatic cancer cell line. An evaluation of 11 mammalian cell lines against 30 novel compounds and two metabolic inhibitors is reported. The inclusion of metabolic inhibitors during an initial screening process, and not simply during mechanistic investigations of a previously identified hit compound, provides a rapid and sensitive tool for identifying drug candidates potentially overlooked by other methods.
Collapse
|
5
|
Hopkins MD, Ozmer GL, Witt RC, Brandeburg ZC, Rogers DA, Keating CE, Petcoff PL, Sheaff RJ, Lamar AA. PhI(OAc) 2 and iodine-mediated synthesis of N-alkyl sulfonamides derived from polycyclic aromatic hydrocarbon scaffolds and determination of their antibacterial and cytotoxic activities. Org Biomol Chem 2021; 19:1133-1144. [PMID: 33443507 DOI: 10.1039/d0ob02429e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The development of new approaches toward chemo- and regioselective functionalization of polycyclic aromatic hydrocarbon (PAH) scaffolds will provide opportunities for the synthesis of novel biologically active small molecules that exploit the high degree of lipophilicity imparted by the PAH unit. Herein, we report a new synthetic method for C-X bond substitution that is speculated to operate via a N-centered radical (NCR) mechanism according to experimental observations. A series of PAH sulfonamides have been synthesized and their biological activity has been evaluated against Gram-negative and Gram-positive bacterial strains (using a BacTiter-Glo assay) along with a series of mammalian cell lines (using CellTiter-Blue and CellTiter-Glo assays). The viability assays have resulted in the discovery of a number of bactericidal compounds that exhibit potency similar to other well-known antibacterials such as kanamycin and tetracycline, along with the discovery of a luciferase inhibitor. Additionally, the physicochemical and drug-likeness properties of the compounds were determined experimentally and using in silico approaches and the results are presented and discussed within.
Collapse
Affiliation(s)
- Megan D Hopkins
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Garett L Ozmer
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Ryan C Witt
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Zachary C Brandeburg
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - David A Rogers
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Claire E Keating
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Presley L Petcoff
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Angus A Lamar
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| |
Collapse
|
6
|
Karki AB, Ballard K, Harper C, Sheaff RJ, Fakhr MK. Staphylococcus aureus enhances biofilm formation, aerotolerance, and survival of Campylobacter strains isolated from retail meats. Sci Rep 2021; 11:13837. [PMID: 34226590 PMCID: PMC8257638 DOI: 10.1038/s41598-021-91743-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 05/26/2021] [Indexed: 02/06/2023] Open
Abstract
In retail meat products, Campylobacter jejuni, C. coli, and Staphylococcus aureus have been reported in high prevalence. The polymicrobial interaction between Campylobacter and other bacteria could enhance Campylobacter survival during the adverse conditions encountered during retail meat processing and storage. This study was designed to investigate the potential role of S. aureus from retail meats in enhancing the survival of Campylobacter exposed to low temperature, aerobic conditions, and biofilm formation. Results indicated that viable S. aureus cells and filter-sterilized cell-free media obtained from S. aureus prolonged the survival of Campylobacter at low temperature and during aerobic conditions. Biofilm formation of Campylobacter strains was significantly enhanced in the presence of viable S. aureus cells, but the results were inconclusive when extracts from cell-free media were used. In conclusion, the presence of S. aureus cells enhances survivability of Campylobacter strains in adverse conditions such as low temperature and aerobic conditions. Further investigations are warranted to understand the interaction between Campylobacter and S. aureus, and effective intervention strategies are needed to reduce the incidence of both foodborne pathogens in retail meat products.
Collapse
Affiliation(s)
- Anand B. Karki
- grid.267360.60000 0001 2160 264XDepartment of Biological Science, The University of Tulsa, Tulsa, OK USA
| | - Kaylee Ballard
- grid.267360.60000 0001 2160 264XDepartment of Biological Science, The University of Tulsa, Tulsa, OK USA
| | - Claudia Harper
- grid.267360.60000 0001 2160 264XDepartment of Biological Science, The University of Tulsa, Tulsa, OK USA
| | - Robert J. Sheaff
- grid.267360.60000 0001 2160 264XDepartment of Chemistry and Biochemistry, The University of Tulsa, Tulsa, OK USA
| | - Mohamed K. Fakhr
- grid.267360.60000 0001 2160 264XDepartment of Biological Science, The University of Tulsa, Tulsa, OK USA
| |
Collapse
|
7
|
Marasini D, Karki AB, Bryant JM, Sheaff RJ, Fakhr MK. Molecular characterization of megaplasmids encoding the type VI secretion system in Campylobacter jejuni isolated from chicken livers and gizzards. Sci Rep 2020; 10:12514. [PMID: 32719325 PMCID: PMC7385129 DOI: 10.1038/s41598-020-69155-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 06/29/2020] [Indexed: 01/06/2023] Open
Abstract
Megaplasmids in Campylobacter spp. likely play important roles in antibiotic resistance, virulence, and horizontal gene transfer. In this study, megaplasmids pCJDM202 (119 kb) and pCJDM67L (116 kb) from C. jejuni strains WP2-202 and OD2-67, respectively, were sequenced and characterized. These megaplasmids contained genes for tetracycline resistance [tet(O)], the Type IV secretion system, conjugative transfer and the Type VI secretion system (T6SS). The T6SS genes in Campylobacter plasmids encoded genes and proteins that were similar to those identified in Campylobacter chromosomal DNA. When the megaplasmid pCJDM202 from C. jejuni WP2-202 was transferred via conjugation to C. jejuni NCTC11168 Nal+, transconconjugants acquired tetracycline resistance and enhanced cytotoxicity towards red blood cells. A T6SS mutant of strain WP2-202 was generated and designated Δhcp3; the mutant was significantly impaired in its ability to lyse red blood cells and survive in defibrinated blood. The cytotoxicity of Campylobacter strains towards the human embryonic kidney cell line HEK 293 was not impacted by the T6SS. In summary, the T6SS encoded by Campylobacter megaplasmids mediates lysis of RBCs and likely contributes to survival on retail meats where blood cells are abundant.
Collapse
Affiliation(s)
- Daya Marasini
- Department of Biological Science, The University of Tulsa, Tulsa, OK, USA
| | - Anand B Karki
- Department of Biological Science, The University of Tulsa, Tulsa, OK, USA
| | - John M Bryant
- Department of Biological Science, The University of Tulsa, Tulsa, OK, USA
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, OK, USA
| | - Mohamed K Fakhr
- Department of Biological Science, The University of Tulsa, Tulsa, OK, USA.
| |
Collapse
|
8
|
Hopkins MD, Abebe FA, Scott KA, Ozmer GL, Sheir AA, Schroeder LJ, Sheaff RJ, Lamar AA. Synthesis and identification of heteroaromatic N-benzyl sulfonamides as potential anticancer agents. Org Biomol Chem 2019; 17:8391-8402. [PMID: 31469373 DOI: 10.1039/c9ob01694e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Sulfonamides are a crucial class of bioisosteres that are prevalent in a wide range of pharmaceuticals, however, the available methods for their production directly from heteroaryl aldehyde reagents remains surprisingly limited. A new approach for regioselective incorporation of a sulfonamide unit to heteroarene scaffolds has been developed and is reported within. As a result, a variety of primary benzylic N-alkylsulfonamides have been prepared via a two-step (one pot) formation from the in situ reduction of an intermediate N-sulfonyl imine under mild, practical conditions. The compounds have been screened against a variety of cell lines for cytotoxicity effects using a Cell Titer Blue assay. The cell viability investigation identifies a subset of N-benzylic sulfonamides derived from the indole scaffold to be targeted for further development into novel molecules with potential therapeutic value. The most cytotoxic of the compounds prepared, AAL-030, exhibited higher potency than other well-known anticancer agents Indisulam and ABT-751.
Collapse
Affiliation(s)
- Megan D Hopkins
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Felagot A Abebe
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Kristina A Scott
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Garett L Ozmer
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Alec A Sheir
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Lucas J Schroeder
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| | - Angus A Lamar
- Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, USA.
| |
Collapse
|
9
|
Elliott ML, Thomas K, Kennedy S, Koduri ND, Hussaini RS, Sheaff RJ. Identification of Novel Proteasome Inhibitors from an Enaminone Library. Chem Biol Drug Des 2015; 86:322-32. [DOI: 10.1111/cbdd.12496] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 11/20/2014] [Accepted: 11/30/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Megan L. Elliott
- Department of Chemistry and Biochemistry; The University of Tulsa; Keplinger Hall, 800 South Tucker Drive, Tulsa OK, 74104 USA
- College of Osteopathic Medicine; Oklahoma State University; 1111 W. 17th St. Tulsa OK, 74107 USA
| | - Kevin Thomas
- Department of Chemistry and Biochemistry; The University of Tulsa; Keplinger Hall, 800 South Tucker Drive, Tulsa OK, 74104 USA
| | - Steven Kennedy
- Department of Chemistry and Biochemistry; The University of Tulsa; Keplinger Hall, 800 South Tucker Drive, Tulsa OK, 74104 USA
- The University of Toronto Structural Genomics Consortium; 101 College St. MaRS South Tower, Suite 700 Toronto ON, M5G 1L7 Canada
| | - Naga D. Koduri
- Department of Chemistry and Biochemistry; The University of Tulsa; Keplinger Hall, 800 South Tucker Drive, Tulsa OK, 74104 USA
| | - R. Syed Hussaini
- Department of Chemistry and Biochemistry; The University of Tulsa; Keplinger Hall, 800 South Tucker Drive, Tulsa OK, 74104 USA
| | - Robert J. Sheaff
- Department of Chemistry and Biochemistry; The University of Tulsa; Keplinger Hall, 800 South Tucker Drive, Tulsa OK, 74104 USA
| |
Collapse
|
10
|
Caruso JF, Lutz BM, Davidson ME, Wilson K, Crane CS, Craig CE, Nissen TE, Mason ML, Coday MA, Sheaff RJ, Potter WT. Salivary Hormonal Values from High-Speed Resistive Exercise Workouts. J Strength Cond Res 2012; 26:625-32. [DOI: 10.1519/jsc.0b013e31822c7267] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
11
|
Bedford R, LePage D, Hoffmann R, Kennedy S, Gutschenritter T, Bull L, Sujijantarat N, DiCesare JC, Sheaff RJ. Luciferase inhibition by a novel naphthoquinone. Journal of Photochemistry and Photobiology B: Biology 2012; 107:55-64. [DOI: 10.1016/j.jphotobiol.2011.11.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 11/25/2011] [Accepted: 11/30/2011] [Indexed: 01/12/2023]
|
12
|
Sherwood VF, Kennedy S, Zhang H, Purser GH, Sheaff RJ. Altered UV absorbance and cytotoxicity of chlorinated sunscreen agents. Cutan Ocul Toxicol 2012; 31:273-9. [DOI: 10.3109/15569527.2011.647181] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
13
|
Carvajal D, Kennedy S, Boustani A, Lazar M, Nguyen S, DiCesare JC, Sheaff RJ. Induction of Cell Death by a Novel Naphthoquinone Containing a Modified Anthracycline Ring System. Chem Biol Drug Des 2011; 78:764-77. [DOI: 10.1111/j.1747-0285.2011.01214.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
14
|
Kennedy S, Dicesare JC, Sheaff RJ. Topoisomerase I inactivation by a novel thiol reactive naphthoquinone. Biochem Biophys Res Commun 2011; 410:152-8. [PMID: 21651895 DOI: 10.1016/j.bbrc.2011.05.131] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 05/21/2011] [Indexed: 01/17/2023]
Abstract
The naphthoquinone adduct 12,13-dihydro-N-methyl-6,11,13-trioxo-5H-benzo[4,5]cyclohepta[1,2-b]naphthalen-5,12-imine (hereafter called TU100) contains structural features of both the anthracycline and isoquinone chemotherapeutics. An initial characterization showed TU100 is cytotoxic to mammalian cells and can inhibit topoisomerase I and II. Analysis using topoisomerase I now reveals TU100 is a slow acting inhibitor targeting the enzyme in the absence of DNA. Diluting pre-incubated TU100 and topoisomerase I failed to alleviate inhibition, suggesting the enzyme is being covalently modified. Critical cysteine thiols were identified as the possible target based on the ability of reducing agents to reverse TU100 inhibition. Consistent with this idea, TU100 protected topoisomerase I from inactivation by the sulfhydryl modifying agent N-ethylmaleimide (NEM). Unlike agents nonspecifically reacting with thiols, however, TU100 is specific for topoisomerase because it failed to inhibit a cysteine dependent protease. These results indicate TU100 is a novel naphthoquinone that inactivates free topoisomerase I via alkylation of cysteine residues.
Collapse
Affiliation(s)
- Steven Kennedy
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, OK 74104, United States
| | | | | |
Collapse
|
15
|
Kennedy S, DiCesare JC, Sheaff RJ. Topoisomerase I/II inhibition by a novel naphthoquinone containing a modified anthracycline ring system. Biochem Biophys Res Commun 2011; 408:94-8. [DOI: 10.1016/j.bbrc.2011.03.126] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 03/26/2011] [Indexed: 10/18/2022]
|
16
|
Palit S, Sheaff RJ, France CR, McGlone ST, Potter WT, Harkness AR, McNulty JL, Bartley EJ, Hoffmann R, Monda JK, Rhudy JL. Serotonin transporter gene (5-HTTLPR) polymorphisms are associated with emotional modulation of pain but not emotional modulation of spinal nociception. Biol Psychol 2011; 86:360-9. [DOI: 10.1016/j.biopsycho.2011.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 01/07/2011] [Accepted: 01/24/2011] [Indexed: 12/18/2022]
|
17
|
Abstract
Disrupted cell cycle machinery is commonly thought to result in loss of proliferative control. Standard therapies target these rapidly dividing cells, yet they are ineffective against pancreatic cancer, suggesting that its development and/or progression might deviate from standard paradigms. Supposedly essential cell cycle components are actually dispensable in mice, and accumulating evidence indicates that they play more diverse roles during apoptosis, signal transduction, and cell migration. A better understanding of how pancreatic cancer cells proliferate and the contribution of disrupted cell cycle machinery would provide much needed opportunities for developing new diagnostic and therapeutic options to improve patient outcome.
Collapse
Affiliation(s)
- Lucas P Nacusi
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minn., USA
| | | |
Collapse
|
18
|
Abstract
BACKGROUND p27kip1 (p27) is a multifunctional protein implicated in regulation of cell cycling, signal transduction, and adhesion. Its activity is controlled in part by Phosphatylinositol-3-Kinase (PI3K)/Akt1 signaling, and disruption of this regulatory connection has been identified in human breast cancers. The serine/threonine protein kinase Akt1 directly phosphorylates p27, so identifying the modified residue(s) is essential for understanding how it regulates p27 function. Various amino acids have been suggested as potential targets, but recent attention has focused on threonine 157 (T157) because it is located in a putative Akt1 consensus site. However, T157 is not evolutionarily conserved between mouse and human. We therefore re-evaluated Akt1 phosphorylation of p27 using purified proteins and in cells. RESULTS Here we show purified Akt1 phosphorylates human and mouse p27 equally well. Phospho-peptide mapping indicates Akt1 targets multiple sites conserved in both species, while phospho-amino acid analysis identifies the targeted residues as serine rather than threonine. P27 deletion mutants localized these sites to the N-terminus, which contains the major p27 phosphorylation site in cells (serine 10). P27 phosphorylated by Akt1 was detected by a phospho-S10 specific antibody, confirming this serine was targeted. Akt1 failed to phosphorylate p27S10A despite evidence of a second site from mapping experiments. This surprising result suggested S10 phosphorylation might be required for targeting the second site. We tested this idea by replacing S10 with threonine, which as expected led to the appearance of phospho-threonine. Phospho-serine was still present, however, confirming Akt1 sequentially targets multiple serines in this region. We took two approaches in an attempt to explain why different residues were previously implicated. A kinetic analysis revealed a putative Akt1 binding site in the C-terminus, which may explain why mutations in this region affect p27 phosphorylation. Furthermore, commercially available recombinant Akt1 preparations exhibit striking differences in substrate specificity and site selectivity. To confirm S10 is a relevant site, we first showed that full-length wild type Akt1 purified from mammalian cells phosphorylates both human and mouse p27 on S10. Finally, we found that in cultured cells under physiologically relevant conditions such as oxidative stress or growth factor deprivation, endogenous Akt1 causes p27 accumulation by phosphorylating S10. CONCLUSION Identifying where Akt1 phosphorylates p27 is essential for understanding its functional implications. We found that full-length wild type Akt1--whether purified, transiently overexpressed in cells, or activated in response to cellular stress--phosphorylates p27 at S10, a noncanonical but evolutionarily conserved site known to regulate p27 activity and stability. Using recombinant Akt1 recapitulating this specificity, we showed modification of p27S10 also leads to phosphorylation of an adjacent serine. These results integrate PI3K/Akt1 signaling in response to stress with p27 regulation through its major phosphorylation site in cells, and thus identify new avenues for understanding p27 deregulation in human cancers.
Collapse
Affiliation(s)
- Lucas P Nacusi
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, Oklahoma 74104, USA
- Department of Biochemistry, molecular Biology and Biophysics, University of Minnesota Cancer Center, University of Minnesota, Minneapolis MN 55455, USA
| | - Robert J Sheaff
- Department of Chemistry and Biochemistry, The University of Tulsa, Tulsa, Oklahoma 74104, USA
- Department of Biochemistry, molecular Biology and Biophysics, University of Minnesota Cancer Center, University of Minnesota, Minneapolis MN 55455, USA
| |
Collapse
|
19
|
Abstract
Multiple proteolytic pathways are involved in the degradation of the cyclin-dependent kinase inhibitor p21(Cip1/WAF1). Timed destruction of p21(Cip1/WAF1) plays a critical role in cell-cycle progression and cellular response to DNA damage. The SCF(Skp2) complex (consisting of Rbx1, Cul1, Skp1, and Skp2) is one of the E3 ubiquitin ligases involved in ubiquitination of p21(Cip1/WAF1). Little is known about how SCF(Skp2) recruits its substrates and selects particular acceptor lysine residues for ubiquitination. In this study, we investigated the requirements for SCF(Skp2) recognition of p21(Cip1/WAF1) and lysine residues that are ubiquitinated in vitro and inside cells. We demonstrate that ubiquitination of p21(Cip1/WAF1) requires a functional interaction between p21(Cip1/WAF1) and the cyclin E-Cdk2 complex. Mutation of both the cyclin E recruitment motif (RXL) and the Cdk2-binding motif (FNF) at the N terminus of p21(Cip1/WAF1) abolishes its ubiquitination by SCF(Skp2), while mutation of either motif alone has minimal effects, suggesting either contact is sufficient for substrate recruitment. Thus, SCF(Skp2) appears to recognize a trimeric complex consisting of cyclin E-Cdk2-p21(Cip1/WAF1). Furthermore, we show that p21(Cip1/WAF1) can be ubiquitinated at four distinct lysine residues located in the carboxyl-terminal region but not two other lysine residues in the N-terminal region. Any one of these four lysine residues can be targeted for ubiquitination in the absence of the others in vitro, and three of these four lysine residues are also ubiquitinated in vivo, suggesting that there is limited specificity in the selection of ubiquitination sites. Interestingly, mutation of the carboxyl-terminal proline to lysine enables ubiquitin conjugation at the carboxyl terminus of the substrate both in vitro and in vivo. Thus, our results highlight a unique property of the ubiquitination enzymatic reaction in that substrate ubiquitination site selection can be remarkably diverse and occur in distinct spatial areas.
Collapse
Affiliation(s)
- Wei Wang
- Department of Chemistry and Biochemistry, University of Colorado-Boulder, Boulder, Colorado 80309, USA
| | | | | | | |
Collapse
|
20
|
Moeller SJ, Sheaff RJ. G1 phase: components, conundrums, context. Results Probl Cell Differ 2006; 42:1-29. [PMID: 16903206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A eukaryotic cell must coordinate DNA synthesis and chromosomal segregation to generate a faithful replica of itself. These events are confined to discrete periods designated synthesis (S) and mitosis (M), and are separated by two gap periods (Gl and G2). A complete proliferative cycle entails sequential and regulated progression through G1, S, G2, and M phases. During G1, cells receive information from the extracellular environment and determine whether to proliferate or to adopt an alternate fate. Work in yeast and cultured mammalian cells has implicated cyclin dependent kinases (Cdks) and their cyclin regulatory partners as key components controlling G1. Unique cyclin/Cdk complexes are temporally expressed in response to extracellular signaling, whereupon they phosphorylate specific targets to promote ordered G1 progression and S phase entry. Cyclins and Cdks are thought to be required and rate-limiting for cell proliferation because manipulating their activity in yeast and cultured mammalian cells alters G1 progression. However, recent evidence suggests that these same components are not necessarily required in developing mouse embryos or cells derived from them. The implications of these intriguing observations for understanding G1 progression and its regulation are discussed.
Collapse
|
21
|
Moeller SJ, Head ED, Sheaff RJ. p27Kip1 inhibition of GRB2-SOS formation can regulate Ras activation. Mol Cell Biol 2003; 23:3735-52. [PMID: 12748278 PMCID: PMC155227 DOI: 10.1128/mcb.23.11.3735-3752.2003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2002] [Revised: 01/30/2003] [Accepted: 03/12/2003] [Indexed: 01/01/2023] Open
Abstract
p27(Kip1) (p27) is often inappropriately downregulated in aggressive human cancers. Although p27 can inhibit cyclin-dependent kinases (CDKs), low p27 does not always correlate with increased CDK activity. Furthermore, cells derived from p27(-/-) mice respond to antimitogens, maintain restriction point control, and do not deregulate CDKs. Thus, disruption of a p27 function other than CDK inhibition may contribute to the disease state. A yeast two-hybrid screen identified growth factor receptor-bound protein 2 (GRB2) as a p27 binding partner. We now demonstrate that p27 can inhibit GRB2 function by blocking its association with the guanine nucleotide exchange factor SOS. Endogenous p27 is rapidly exported from the nucleus to the cytoplasm in response to mitogen stimulation, where it binds GRB2 concomitant with a decrease in GRB2-associated SOS. As predicted, mitogen-stimulated p27(-/-) cells maintained their GRB2-SOS complexes for significantly longer. The Ras/mitogen-activated protein kinase pathway does not appear to be deregulated in cells lacking p27 despite excess GRB2-SOS, suggesting that additional control mechanisms are present. A transient-transfection approach was employed to show that p27 can inhibit Ras activation by targeting GRB2 and further revealed that the CDK and GRB2 inhibitory functions of p27 are separable and distinct. Thus, p27 downregulation may compromise control of Ras, one of the most common oncogenic events in human cancer.
Collapse
Affiliation(s)
- Stephanie J Moeller
- University of Minnesota Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | | |
Collapse
|
22
|
Nho RS, Sheaff RJ. p27kip1 contributions to cancer. Prog Cell Cycle Res 2003; 5:249-59. [PMID: 14593719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Deregulation of the tumor suppressor p27kip1 (p27) has been implicated in a variety of human cancers, suggesting it might be a viable therapeutic target. Developing p27-specific intervention strategies requires understanding its role and regulation in normal and pathologic states. Although p27 has been extensively characterized as an inhibitor of cyclin-dependent kinases, disruption of this function is inadequate to explain its role in tumorigenesis. A more comprehensive understanding of p27 biology would facilitate development of therapeutic responses to p27 disruption in human cancers.
Collapse
Affiliation(s)
- Richard Seonghun Nho
- Cancer Center, MMC 806, 420 Delaware St. SE, University of Minnesota, Minneapolis, MN 55455, USA
| | | |
Collapse
|
23
|
Abstract
The Cdk inhibitor p21Cip1 is an unstable protein. Pharmacologic inhibition of the proteasome increases the half-life of p21 from less than 30 min to more than 2 hr and results in the accumulation of p21-ubiquitin conjugates. To determine whether ubiquitination was required for proteasomal degradation of p21, we constructed mutant versions of p21 that were not ubiquitinated in vivo. Remarkably, these mutants remained unstable and increased in abundance upon proteasome inhibition, indicating that direct ubiquitination of p21 is not necessary for its turnover by the proteasome. The frequently observed correlation between protein ubiquitination and proteasomal degradation is insufficient to conclude that ubiquitination is a prerequisite for degradation.
Collapse
Affiliation(s)
- R J Sheaff
- University of Minnesota Cancer Center and Department of Biochemistry, University of Minnesota, Minneapolis 55455, USA
| | | | | | | | | | | |
Collapse
|
24
|
Affiliation(s)
- R J Sheaff
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
| | | |
Collapse
|
25
|
Abstract
CDK inhibitors are thought to prevent cell proliferation by negatively regulating cyclin-CDK complexes. We propose that the opposite is also true, that cyclin-CDK complexes in mammmalian cells can promote cell cycle progression by directly down-regulating CDK inhibitors. We show that expression of cyclin E-CDK2 in murine fibroblasts causes phosphorylation of the CDK inhibitor p27Kip1 on T187, and that cyclin E-CDK2 can directly phosphorylate p27 T187 in vitro. We further show that cyclin E-CDK2-dependent phosphorylation of p27 results in elimination of p27 from the cell, allowing cells to transit from G1 to S phase. Moreover, mutation of T187 in p27 to alanine creates a p27 protein that causes a G1 block resistant to cyclin E and whose level of expression is not modulated by cyclin E. A kinetic analysis of the interaction between p27 and cyclin E-CDK2 explains how p27 can be regulated by the same enzyme it targets for inhibition. We show that p27 interacts with cyclin E-CDK2 in at least two distinct ways: one resulting in p27 phosphorylation and release, the other in tight binding and cyclin E-CDK2 inhibition. The binding of ATP to the CDK governs which state predominates. At low ATP (< 50 microM) p27 is primarily a CDK inhibitor, but at ATP concentrations approaching physiological levels (> 1 mM) p27 is more likely to be a substrate. Thus, we have identified p27 as a biologically relevant cyclin E-CDK2 substrate, demonstrated the physiological consequences of p27 phosphorylation, and developed a kinetic model to explain how p27 can be both an inhibitor and a substrate of cyclin E-CDK2.
Collapse
Affiliation(s)
- R J Sheaff
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center (FHCRC), Seattle, Washington 98104, USA
| | | | | | | | | |
Collapse
|
26
|
Affiliation(s)
- R J Sheaff
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA
| |
Collapse
|
27
|
Abstract
Cyclin-dependent kinase inhibitors (CKIs) are crucial regulators of cell-cycle progression. The CKI Sic1 controls the timing of DNA replication by inhibiting Clb-Cdc28 kinase. Phosphorylation of Sic1 by CIn-Cdc28 kinase alleviates this inhibition by targeting Sic1 for degradation through the ubiquitin-mediated proteolytic pathway.
Collapse
Affiliation(s)
- R J Sheaff
- Department of Basic Sciences, Fred Hutchinson Cancer Research Center, 1124 Columbia Street, Seattle, WA 98104, USA
| | | |
Collapse
|
28
|
Clurman BE, Sheaff RJ, Thress K, Groudine M, Roberts JM. Turnover of cyclin E by the ubiquitin-proteasome pathway is regulated by cdk2 binding and cyclin phosphorylation. Genes Dev 1996; 10:1979-90. [PMID: 8769642 DOI: 10.1101/gad.10.16.1979] [Citation(s) in RCA: 385] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cyclin E is a mammalian G1 cyclin that is both required and rate limiting for entry into S phase. The expression of cyclin E is periodic, peaking at the G1-S transition and then decaying as S phase progresses. To understand the mechanisms underlying cyclin E periodicity, we have investigated the regulation of cyclin E degradation. We find that cyclin E is degraded by the ubiquitin-proteasome system, and that this degradation is regulated by both cdk2 binding and cdk2 catalytic activity. Free cyclin E is readily ubiquitinated and degraded by the proteasome. Binding to cdk2 protects cyclin E from ubiquitination, and this protection is reversed by cdk2 activity in a process that involves phosphorylation of cyclin E itself. The data are most consistent with a model in which cdk2 activity initiates cyclin E degradation by promoting the disassembly of cyclin E-cdk2 complexes, followed by the ubiquitination and degradation of free cyclin E.
Collapse
Affiliation(s)
- B E Clurman
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA
| | | | | | | | | |
Collapse
|
29
|
Abstract
The interactions of calf thymus DNA polymerase alpha (pol alpha) with primer/templates were examined. Simply changing the primer from DNA to RNA had little effect on primer/template binding or dNTP polymerization (Km, Vmax and processivity). Surprisingly, however, adding a 5'-triphosphate to the primer greatly changed its interactions with pol alpha (binding, Vmax and Km and processivity). While changing the primer from DNA to RNA greatly altered the abilit of pol alpha to discriminate against nucleotide analogs, it did not compromise the ability of pol alpha to discriminate against non-cognate dNTPs. Thus the nature of the primer appears to affect 'sugar fidelity', without altering 'base fidelity'. DNase protection assays showed that pol alpha strongly protected 9 nt of the primer strand, 13 nt of the duplex template strand and 14 nt of the single-stranded template from hydrolysis by DNase I and weakly protected several bases outside this core region. This large DNA binding domain may account for the ability of a 5'-triphosphate on RNA primers to alter the catalytic properties of pol alpha.
Collapse
Affiliation(s)
- H C Thompson
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215, USA
| | | | | |
Collapse
|
30
|
Abstract
Increasingly, biochemical and genetic evidence indicates that mutations in the gene encoding p16, an inhibitor of cyclin-dependent kinases, may play a role in some forms of hereditary and sporadic tumors.
Collapse
Affiliation(s)
- R J Sheaff
- Department of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104
| | | |
Collapse
|
31
|
Sheaff RJ, Kuchta RD. Misincorporation of nucleotides by calf thymus DNA primase and elongation of primers containing multiple noncognate nucleotides by DNA polymerase alpha. J Biol Chem 1994; 269:19225-31. [PMID: 8034683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Misincorporation of nucleotides by calf thymus DNA primase was examined using synthetic DNA templates of defined sequence. Primase seldom misincorporated NTPs during initiation of a new primer (i.e. polymerization of two NTPs to generate the dinucleotide). Following dinucleotide formation, however, primase readily misincorporated NTPs. Although the rate of misincorporation varied according to both the identity of the mismatch and the template sequence, primase is by far the least accurate nucleotide-polymerizing enzyme known. In some cases primase discriminated against incorrect NTPs by less than a factor of 100. After primase incorporated a noncognate nucleotide into the primer, the next correct NTP was readily added. Remarkably, primase could also polymerize consecutive noncognate nucleotides and generate primers containing multiple mismatches. Generation of a correctly base-paired primer-template negatively regulated further primer synthesis; however, generation of a primer-template containing multiple mismatches did not. After primase synthesized a primer containing multiple mismatches, the primer was transferred to the polymerase alpha active site via an intramolecular mechanism. Importantly, polymerase alpha readily elongated this primer if dNTPs were present. These data are discussed with respect to the question of why primase is required for DNA replication.
Collapse
Affiliation(s)
- R J Sheaff
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215
| | | |
Collapse
|
32
|
Sheaff RJ, Kuchta RD, Ilsley D. Calf thymus DNA polymerase alpha-primase: "communication" and primer-template movement between the two active sites. Biochemistry 1994; 33:2247-54. [PMID: 8117681 DOI: 10.1021/bi00174a035] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The DNA polymerase alpha-primase complex replicates single-stranded DNA by first synthesizing a short RNA primer (primase) which is then further elongated by the incorporation of dNTPs (DNA polymerase alpha). While primase and pol alpha function independently prior to synthesis of an RNA primer, the two activities become coordinated after primer synthesis. After primase generates a primer-template, it moves from the primase active site to the pol alpha active site for further elongation without dissociating into solution. Intramolecular transfer occurs immediately after primer synthesis and is employed on both long templates such as poly(dT) and short synthetic templates (< or = 60 nucleotides). Primer-template transfer and elongation by pol alpha are rapid compared to primer synthesis. After pol alpha elongates the primer, primase reinitiates primer synthesis, and the cycle is repeated. However, if dNTPs are absent such that primer elongation cannot occur, further primase activity is inhibited after a single round of primer synthesis. This "negative regulation" of primase activity is mediated by the newly generated primer-template provided the following conditions are met: (1) Primase synthesizes the primer; (2) the primer is 7-10 nucleotides long and remains bound to the template; (3) the template is of sufficient length; (4) the primer-template dissociates slowly from the enzyme complex; and (5) the primer-template interacts with the pol alpha active site. Polymerization of multiple dNTPs by pol alpha rapidly reactivates primase; hence, negative regulation of primase activity likely ensures a new primer is not synthesized until the previous one has been elongated by pol alpha.
Collapse
Affiliation(s)
- R J Sheaff
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215
| | | | | |
Collapse
|
33
|
Abstract
The mechanism by which calf thymus DNA primase synthesizes RNA primers was examined. Primase first binds a single-stranded DNA template (KD << 100 nM) and can then slide along the DNA in order to find a start for initiating primer synthesis. NTP binding appears ordered, such that the NTP which eventually becomes the second nucleotide of the primer binds the E.DNA complex first. The NTP that becomes the second nucleotide of the primer thereby influences where primase initiates. Primer synthesis is remarkably slow (0.0027 s-1 at 20 microM NTP). The rate-limiting step is after formation of the E.DNA.NTP.NTP complex and before or during dinucleotide synthesis. After synthesis of the dinucleotide, additional NTPs are rapidly polymerized. Primase products are 2-10 nucleotides long. If the enzyme fails to synthesize a primer at least 7 nucleotides long, it reinitiates rather than dissociating from the template. Once a primer at least 7 nucleotides long has been generated, however, subsequent primase activity is inhibited. This inhibition is due to the generation of a stable primer-template complex, which likely remains associated with pol alpha.primase. The role of primase is to synthesize primers that pol alpha can elongate. The ability of primase to distinguish between primers at least 7 nucleotides long and shorter products therefore likely reflects the fact that pol alpha only utilizes primers at least 7 nucleotides long.
Collapse
Affiliation(s)
- R J Sheaff
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215
| | | |
Collapse
|