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Sanders J, Castiglione M, Shun T, Vollmer LL, Schurdak ME, Vogt A, Schwacha A. Validation of a high throughput screening assay to identify small molecules that target the eukaryotic replicative helicase. SLAS DISCOVERY : ADVANCING LIFE SCIENCES R & D 2022; 27:229-241. [PMID: 35058181 PMCID: PMC9196137 DOI: 10.1016/j.slasd.2021.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Mcm2-7 is the catalytic core of the eukaryotic replicative helicase, which together with CDC45 and the GINS complex unwind parental DNA to generate templates for DNA polymerase. Being a highly regulated and complex enzyme that operates via an incompletely understood multi-step mechanism, molecular probes of Mcm2-7 that interrogate specific mechanistic steps would be useful tools for research and potential future chemotherapy. Based upon a synthetic lethal approach, we previously developed a budding yeast multivariate cell-based high throughput screening (HTS) assay to identify putative Mcm inhibitors by their ability to specifically cause a growth defect in an mcm mutant relative to a wild-type strain[1]. Here, as proof of concept, we used this assay to screen a 1280-member compound library (LOPAC) for potential Mcm2-7 inhibitors. Primary screening and dose-dependent retesting identified twelve compounds from this library that specifically inhibited the growth of the Mcm mutant relative to the corresponding wild-type strain (0.9 % hit rate). Secondary assays were employed to rule out non-specific DNA damaging agents, establish direct protein-ligand interaction via biophysical methods, and verify in vivo DNA replication inhibition via fluorescence activated cell sorter analysis (FACS). We identified one agent (β-carboline-3-carboxylic acid N-methylamide, CMA) that physically bound to the purified Mcm2-7 complex (Kdapp119 µM), and at slightly higher concentrations specifically blocked S-phase cell cycle progression of the wild-type strain. In total, identification of Mcm2-7 as a CMA target validates our synthetic lethal HTS assay paradigm as a tool to identify chemical probes for the Mcm2-7 replicative helicase.
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Affiliation(s)
- Jordan Sanders
- The Department of Biological Sciences, University of Pittsburgh, Pittsburgh PA 15260
| | - Michael Castiglione
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
| | - Tongying Shun
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
| | - Laura L Vollmer
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
| | - Mark E Schurdak
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260; Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh PA 15260
| | - Andreas Vogt
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260; Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh PA 15260.
| | - Anthony Schwacha
- The Department of Biological Sciences, University of Pittsburgh, Pittsburgh PA 15260.
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Sausen CW, Bochman ML. Overcoming stochastic variations in culture variables to quantify and compare growth curve data. Bioessays 2021; 43:e2100108. [PMID: 34128245 DOI: 10.1002/bies.202100108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/26/2021] [Accepted: 05/31/2021] [Indexed: 11/06/2022]
Abstract
The comparison of growth, whether it is between different strains or under different growth conditions, is a classic microbiological technique that can provide genetic, epigenetic, cell biological, and chemical biological information depending on how the assay is used. When employing solid growth media, this technique is limited by being largely qualitative and low throughput. Collecting data in the form of growth curves, especially automated data collection in multi-well plates, circumvents these issues. However, the growth curves themselves are subject to stochastic variation in several variables, most notably the length of the lag phase, the doubling rate, and the maximum expansion of the culture. Thus, growth curves are indicative of trends but cannot always be conveniently averaged and statistically compared. Here, we summarize a simple method to compile growth curve data into a quantitative format that is amenable to statistical comparisons and easy to graph and display.
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Affiliation(s)
- Christopher W Sausen
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana, USA.,Pfizer Inc., Andover, Massachusetts, USA
| | - Matthew L Bochman
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana, USA
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Simmons RH, Rogers CM, Bochman ML. A deep dive into the RecQ interactome: something old and something new. Curr Genet 2021; 67:761-767. [PMID: 33961099 DOI: 10.1007/s00294-021-01190-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/21/2021] [Accepted: 04/23/2021] [Indexed: 11/26/2022]
Abstract
RecQ family helicases are found in all domains of life and play roles in multiple processes that underpin genomic integrity. As such, they are often referred to as guardians or caretakers of the genome. Despite their importance, however, there is still much we do not know about their basic functions in vivo, nor do we fully understand how they interact in organisms that encode more than one RecQ family member. We recently took a multi-omics approach to better understand the Saccharomyces cerevisiae Hrq1 helicase and its interaction with Sgs1, with these enzymes being the functional homologs of the disease-linked RECQL4 and BLM helicases, respectively. Using synthetic genetic array analyses, immuno-precipitation coupled to mass spectrometry, and RNA-seq, we found that Hrq1 and Sgs1 likely participate in many pathways outside of the canonical DNA recombination and repair functions for which they are already known. For instance, connections to transcription, ribosome biogenesis, and chromatin/chromosome organization were uncovered. These recent results are briefly detailed with respect to current knowledge in the field, and possible follow-up experiments are suggested. In this way, we hope to gain a wholistic understanding of these RecQ helicases and how their mutation leads to genomic instability.
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Affiliation(s)
- Robert H Simmons
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN, USA
| | - Cody M Rogers
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN, USA
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Matthew L Bochman
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN, USA.
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Ononye OE, Sausen CW, Balakrishnan L, Bochman ML. Lysine acetylation regulates the activity of nuclear Pif1. J Biol Chem 2020; 295:15482-15497. [PMID: 32878983 DOI: 10.1074/jbc.ra120.015164] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/28/2020] [Indexed: 12/16/2022] Open
Abstract
In Saccharomyces cerevisiae, the Pif1 helicase functions in both nuclear and mitochondrial DNA replication and repair processes, preferentially unwinding RNA:DNA hybrids and resolving G-quadruplex structures. We sought to determine how the various activities of Pif1 are regulated in vivo Here, we report lysine acetylation of nuclear Pif1 and demonstrate that it influences both Pif1's cellular roles and core biochemical activities. Using Pif1 overexpression toxicity assays, we determined that the acetyltransferase NuA4 and deacetylase Rpd3 are primarily responsible for the dynamic acetylation of nuclear Pif1. MS analysis revealed that Pif1 was modified in several domains throughout the protein's sequence on the N terminus (Lys-118 and Lys-129), helicase domain (Lys-525, Lys-639, and Lys-725), and C terminus (Lys-800). Acetylation of Pif1 exacerbated its overexpression toxicity phenotype, which was alleviated upon deletion of its N terminus. Biochemical assays demonstrated that acetylation of Pif1 stimulated its helicase, ATPase, and DNA-binding activities, whereas maintaining its substrate preferences. Limited proteolysis assays indicate that acetylation of Pif1 induces a conformational change that may account for its altered enzymatic properties. We propose that acetylation is involved in regulating of Pif1 activities, influencing a multitude of DNA transactions vital to the maintenance of genome integrity.
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Affiliation(s)
- Onyekachi E Ononye
- Department of Biology, School of Science, Indiana University, Purdue University Indianapolis, Indianapolis, Indiana, USA
| | - Christopher W Sausen
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, Indiana, USA
| | - Lata Balakrishnan
- Department of Biology, School of Science, Indiana University, Purdue University Indianapolis, Indianapolis, Indiana, USA.
| | - Matthew L Bochman
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, Indiana, USA.
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Nmezi B, Vollmer LL, Shun TY, Gough A, Rolyan H, Liu F, Jia Y, Padiath QS, Vogt A. Development and Optimization of a High-Content Analysis Platform to Identify Suppressors of Lamin B1 Overexpression as a Therapeutic Strategy for Autosomal Dominant Leukodystrophy. SLAS DISCOVERY : ADVANCING LIFE SCIENCES R & D 2020; 25:939-949. [PMID: 32349647 PMCID: PMC7755098 DOI: 10.1177/2472555220915821] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Autosomal dominant leukodystrophy (ADLD) is a fatal, progressive adult-onset disease characterized by widespread central nervous system (CNS) demyelination and significant morbidity. The late age of onset together with the relatively slow disease progression provides a large therapeutic window for the disorder. However, no treatment exists for ADLD, representing an urgent and unmet clinical need. We have previously shown that ADLD is caused by duplications of the lamin B1 gene causing increased expression of the lamin B1 protein, a major constituent of the nuclear lamina, and demonstrated that transgenic mice with oligodendrocyte-specific overexpression of lamin B1 exhibit temporal and histopathological features reminiscent of the human disease. As increased levels of lamin B1 are the causative event triggering ADLD, approaches aimed at reducing lamin B1 levels and associated functional consequences represent a promising strategy for discovery of small-molecule ADLD therapeutics. To this end, we have created an inducible cell culture model of lamin B1 overexpression and developed high-content analysis in connection with multivariate analysis to define, analyze, and quantify lamin B1 expression and its associated abnormal nuclear phenotype in mouse embryonic fibroblasts (MEFs). The assay has been optimized to meet high-throughput screening (HTS) criteria in multiday variability studies. To control for batch-to-batch variation in the primary MEFs, we have implemented a screening strategy that employs sentinel cells to avoid costly losses during HTS. We posit the assay will identify bona fide suppressors of lamin B1 pathophysiology as candidates for development into potential therapies for ADLD.
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Affiliation(s)
- Bruce Nmezi
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261
| | - Laura L. Vollmer
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
| | - Tong Ying Shun
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
| | - Albert Gough
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
- Department of Computational and Systems Biology, University of Pittsburgh Medical School, Pittsburgh PA 15260
| | - Harshvardhan Rolyan
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261
- Current address: Department of Internal Medicine, Yale University, New Haven, CT
| | - Fang Liu
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261
| | - Yumeng Jia
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261
| | - Quasar S. Padiath
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261
| | - Andreas Vogt
- Drug Discovery Institute, University of Pittsburgh Medical School, Pittsburgh PA 15260
- Department of Computational and Systems Biology, University of Pittsburgh Medical School, Pittsburgh PA 15260
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