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Hays M. Genetic conflicts in budding yeast: The 2μ plasmid as a model selfish element. Semin Cell Dev Biol 2024; 161-162:31-41. [PMID: 38598944 DOI: 10.1016/j.semcdb.2024.04.002] [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: 09/26/2023] [Revised: 04/02/2024] [Accepted: 04/04/2024] [Indexed: 04/12/2024]
Abstract
Antagonistic coevolution, arising from genetic conflict, can drive rapid evolution and biological innovation. Conflict can arise both between organisms and within genomes. This review focuses on budding yeasts as a model system for exploring intra- and inter-genomic genetic conflict, highlighting in particular the 2-micron (2μ) plasmid as a model selfish element. The 2μ is found widely in laboratory strains and industrial isolates of Saccharomyces cerevisiae and has long been known to cause host fitness defects. Nevertheless, the plasmid is frequently ignored in the context of genetic, fitness, and evolution studies. Here, I make a case for further exploring the evolutionary impact of the 2μ plasmid as well as other selfish elements of budding yeasts, discuss recent advances, and, finally, future directions for the field.
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Affiliation(s)
- Michelle Hays
- Department of Genetics, Stanford University, Stanford, CA, United States.
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2
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Mereshchuk A, Johnstone PS, Chew JSK, Dobson MJ. The yeast 2-micron plasmid Rep2 protein has Rep1-independent partitioning function. Nucleic Acids Res 2022; 50:10571-10585. [PMID: 36156142 PMCID: PMC9561267 DOI: 10.1093/nar/gkac810] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 08/18/2022] [Accepted: 09/08/2022] [Indexed: 11/13/2022] Open
Abstract
Equal partitioning of the multi-copy 2-micron plasmid of the budding yeast Saccharomyces cerevisiae requires association of the plasmid Rep1 and Rep2 proteins with the plasmid STB partitioning locus. Determining how the Rep proteins contribute has been complicated by interactions between the components. Here, each Rep protein was expressed fused to the DNA-binding domain of the bacterial repressor protein LexA in yeast harboring a replication-competent plasmid that had LexA-binding sites but lacked STB. Plasmid transmission to daughter cells was increased only by Rep2 fusion expression. Neither Rep1 nor a functional RSC2 complex (a chromatin remodeler required for 2-micron plasmid partitioning) were needed for the improvement. Deletion analysis showed the carboxy-terminal 65 residues of Rep2 were required and sufficient for this Rep1-independent inheritance. Mutation of a conserved basic motif in this domain impaired Rep1-independent and Rep protein/STB-dependent plasmid partitioning. Our findings suggest Rep2, which requires Rep1 and the RSC2 complex for functional association with STB, directly participates in 2-micron plasmid partitioning by linking the plasmid to a host component that is efficiently partitioned during cell division. Further investigation is needed to reveal the host factor targeted by Rep2 that contributes to the survival of these plasmids in their budding yeast hosts.
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Affiliation(s)
- Anastasiia Mereshchuk
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Peter S Johnstone
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Joyce S K Chew
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Melanie J Dobson
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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3
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The selfish yeast plasmid utilizes the condensin complex and condensed chromatin for faithful partitioning. PLoS Genet 2021; 17:e1009660. [PMID: 34270553 PMCID: PMC8318298 DOI: 10.1371/journal.pgen.1009660] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 07/28/2021] [Accepted: 06/10/2021] [Indexed: 11/19/2022] Open
Abstract
Equipartitioning by chromosome association and copy number correction by DNA amplification are at the heart of the evolutionary success of the selfish yeast 2-micron plasmid. The present analysis reveals frequent plasmid presence near telomeres (TELs) and centromeres (CENs) in mitotic cells, with a preference towards the former. Inactivation of Cdc14 causes plasmid missegregation, which is correlated to the non-disjunction of TELs (and of rDNA) under this condition. Induced missegregation of chromosome XII, one of the largest yeast chromosomes which harbors the rDNA array and is highly dependent on the condensin complex for proper disjunction, increases 2-micron plasmid missegregation. This is not the case when chromosome III, one of the smallest chromosomes, is forced to missegregate. Plasmid stability decreases when the condensin subunit Brn1 is inactivated. Brn1 is recruited to the plasmid partitioning locus (STB) with the assistance of the plasmid-coded partitioning proteins Rep1 and Rep2. Furthermore, in a dihybrid assay, Brn1 interacts with Rep1-Rep2. Taken together, these findings support a role for condensin and/or condensed chromatin in 2-micron plasmid propagation. They suggest that condensed chromosome loci are among favored sites utilized by the plasmid for its chromosome-associated segregation. By homing to condensed/quiescent chromosome locales, and not over-perturbing genome homeostasis, the plasmid may minimize fitness conflicts with its host. Analogous persistence strategies may be utilized by other extrachromosomal selfish genomes, for example, episomes of mammalian viruses that hitchhike on host chromosomes for their stable maintenance.
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Yang J, Tian Y, Liu H, Kan Y, Zhou Y, Wang Y, Luo Y. Harnessing the Endogenous 2μ Plasmid of Saccharomyces cerevisiae for Pathway Construction. Front Microbiol 2021; 12:679665. [PMID: 34220765 PMCID: PMC8249740 DOI: 10.3389/fmicb.2021.679665] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 05/18/2021] [Indexed: 02/05/2023] Open
Abstract
pRS episomal plasmids are widely used in Saccharomyces cerevisiae, owing to their easy genetic manipulations and high plasmid copy numbers (PCNs). Nevertheless, their broader application is hampered by the instability of the pRS plasmids. In this study, we designed an episomal plasmid based on the endogenous 2μ plasmid with both improved stability and increased PCN, naming it p2μM, a 2μ-modified plasmid. In the p2μM plasmid, an insertion site between the REP1 promoter and RAF1 promoter was identified, where the replication (ori) of Escherichia coli and a selection marker gene of S. cerevisiae were inserted. As a proof of concept, the tyrosol biosynthetic pathway was constructed in the p2μM plasmid and in a pRS plasmid (pRS423). As a result, the p2μM plasmid presented lower plasmid loss rate than that of pRS423. Furthermore, higher tyrosol titers were achieved in S. cerevisiae harboring p2μM plasmid carrying the tyrosol pathway-related genes. Our study provided an improved genetic manipulation tool in S. cerevisiae for metabolic engineering applications, which may be widely applied for valuable product biosynthesis in yeast.
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Affiliation(s)
- Jing Yang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
| | - Yujuan Tian
- Department of Gastroenterology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Huayi Liu
- Department of Gastroenterology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yeyi Kan
- Department of Gastroenterology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yi Zhou
- Department of Gastroenterology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Ying Wang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
| | - Yunzi Luo
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China.,Department of Gastroenterology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
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Zeng BX, Yao MD, Xiao WH, Luo YZ, Wang Y, Yuan YJ. Endogenous 2μ Plasmid Editing for Pathway Engineering in Saccharomyces cerevisiae. Front Microbiol 2021; 12:631462. [PMID: 33664720 PMCID: PMC7921170 DOI: 10.3389/fmicb.2021.631462] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 01/22/2021] [Indexed: 02/05/2023] Open
Abstract
In Saccharomyces cerevisiae, conventional 2μ-plasmid based plasmid (pC2μ, such as pRS425) have been widely adopted in pathway engineering for multi-copy overexpression of key genes. However, the loss of partition and copy number control elements of yeast endogenous 2μ plasmid (pE2μ) brings the issues concerning plasmid stability and copy number of pC2μ, especially in long-term fermentation. In this study, we developed a method based on CRISPR/Cas9 to edit pE2μ and built the pE2μ multi-copy system by insertion of the target DNA element and elimination of the original pE2μ plasmid. The resulting plasmid pE2μRAF1 and pE2μREP2 demonstrated higher copy number and slower loss rate than a pC2μ control plasmid pRS425RK, when carrying the same target gene. Then, moving the essential gene TPI1 (encoding triose phosphate isomerase) from chromosome to pE2μRAF1 could increase the plasmid viability to nearly 100% and further increase the plasmid copy number by 73.95%. The expression using pE2μ multi-copy system demonstrated much smaller cell-to-cell variation comparing with pC2μ multi-copy system. With auxotrophic complementation of TPI1, the resulting plasmid pE2μRT could undergo cultivation of 90 generations under non-selective conditions without loss. Applying pE2μ multi-copy system for dihydroartemisinic acid (DHAA) biosynthesis, the production of DHAA was increased to 620.9 mg/L at shake-flask level in non-selective rich medium. This titer was 4.73-fold of the strain constructed based on pC2μ due to the more stable pE2μ plasmid system and with higher plasmid copy number. This study provides an improved expression system in yeast, and set a promising platform to construct biosynthesis pathway for valuable products.
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Affiliation(s)
- Bo-Xuan Zeng
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
| | - Ming-Dong Yao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
| | - Wen-Hai Xiao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
| | - Yun-Zi Luo
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Department of Gastroenterology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Ying Wang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
| | - Ying-Jin Yuan
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
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Ma CH, Su BY, Maciaszek A, Fan HF, Guga P, Jayaram M. A Flp-SUMO hybrid recombinase reveals multi-layered copy number control of a selfish DNA element through post-translational modification. PLoS Genet 2019; 15:e1008193. [PMID: 31242181 PMCID: PMC6594588 DOI: 10.1371/journal.pgen.1008193] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 05/13/2019] [Indexed: 12/30/2022] Open
Abstract
Mechanisms for highly efficient chromosome-associated equal segregation, and for maintenance of steady state copy number, are at the heart of the evolutionary success of the 2-micron plasmid as a stable multi-copy extra-chromosomal selfish DNA element present in the yeast nucleus. The Flp site-specific recombination system housed by the plasmid, which is central to plasmid copy number maintenance, is regulated at multiple levels. Transcription of the FLP gene is fine-tuned by the repressor function of the plasmid-coded partitioning proteins Rep1 and Rep2 and their antagonist Raf1, which is also plasmid-coded. In addition, the Flp protein is regulated by the host’s post-translational modification machinery. Utilizing a Flp-SUMO fusion protein, which functionally mimics naturally sumoylated Flp, we demonstrate that the modification signals ubiquitination of Flp, followed by its proteasome-mediated degradation. Furthermore, reduced binding affinity and cooperativity of the modified Flp decrease its association with the plasmid FRT (Flp recombination target) sites, and/or increase its dissociation from them. The resulting attenuation of strand cleavage and recombination events safeguards against runaway increase in plasmid copy number, which is deleterious to the host—and indirectly—to the plasmid. These results have broader relevance to potential mechanisms by which selfish genomes minimize fitness conflicts with host genomes by holding in check the extra genetic load they pose. Plasmids of budding yeasts, exemplified by the 2-micron plasmid of Saccharomyces cerevisiae, and mammalian papilloma and gammaherpes viruses typify eukaryotic extra-chromosomal selfish DNA elements. The plasmid and the viral episomes, despite the long evolutionary divergence of their hosts, share striking similarities in lifestyles. These include the ability to segregate to daughter cells by hitchhiking on chromosomes and to switch from cell cycle regulated replication to iterative replication for copy number maintenance. While selfish elements, including those integrated into chromosomes, rely on their hosts’ genetic potential for long-term survival, their genetic load is carefully regulated to minimize fitness conflicts with the hosts. Our study focuses on the Flp site-specific recombinase, which is central to the copy number control of the 2-micron plasmid and whose steady state levels are regulated through transcriptional control by plasmid coded proteins and through post-translational modification by the host’s sumoylation machinery. We demonstrate that sumoylation, in addition, attenuates the catalytic activity of Flp by diminishing its DNA binding affinity and inter-monomer cooperativity, providing another layer of protection against runaway increase in plasmid copy number. Population control by self-imposed and host-mediated mechanisms is likely a general strategy among selfish elements to ensure nearly conflict-free coexistence with host genomes.
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Affiliation(s)
- Chien-Hui Ma
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, United States of America
| | - Bo-Yu Su
- Department of Life Sciences and Institute of Genome Sciences, Biophotonics and Molecular Imaging Research Center, National Yang-Ming University, Taipei City, Taiwan
| | - Anna Maciaszek
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry, Lodz, Poland
| | - Hsiu-Fang Fan
- Department of Life Sciences and Institute of Genome Sciences, Biophotonics and Molecular Imaging Research Center, National Yang-Ming University, Taipei City, Taiwan
| | - Piotr Guga
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry, Lodz, Poland
| | - Makkuni Jayaram
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, United States of America
- * E-mail:
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Insights into the DNA sequence elements required for partitioning and copy number control of the yeast 2-micron plasmid. Curr Genet 2019; 65:887-892. [PMID: 30915516 DOI: 10.1007/s00294-019-00958-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 03/15/2019] [Accepted: 03/16/2019] [Indexed: 10/27/2022]
Abstract
The yeast 2-micron plasmid is an almost perfect selfish DNA. The entire coding capacity of the plasmid is dedicated to ensuring its own inheritance, with no benefit to its host. Despite high copy number, the plasmid confers no phenotype. It manages this feat by possessing mechanisms for plasmid copy-number control and for partitioning. The former increases plasmid numbers when they fall, but is repressed at high copy number, while the latter ensures 2-micron copies are equally partitioned during host cell division. Although the plasmid amplification mechanism is well established, the partitioning system and the means by which the 2-micron plasmid partitioning proteins, Rep1 and Rep2, regulate plasmid copy number remain incompletely understood. This review focuses on recent efforts to determine the nature of Rep protein complexes formed at the plasmid stability locus (STB) and at plasmid gene promoters, the identity of DNA sequence elements required for Rep protein association, and the mechanism by which the Rep proteins manage their dual roles of plasmid partitioning and plasmid gene repression.
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Hohnholz R, Achstetter T. Recombinant multicopy plasmids in yeast – interactions with the endogenous 2 μm. FEMS Yeast Res 2019; 19:5425451. [DOI: 10.1093/femsyr/foz001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 02/09/2019] [Indexed: 12/16/2022] Open
Abstract
ABSTRACT
Flp-mediated site specific intramolecular recombination in Saccharomyces cerevisiae is considered responsible for amplification of the endogenous 2 μm plasmid. For YEp-type vectors, a similar mechanism can be imagined by which such plasmids achieve high copy numbers, a trait desired for many research applications and necessary for industrial production. We have cultivated yeast carrying one of six isomeric YEp-type model expression plasmids under two different conditions and back transformed the shuttle vectors into Escherichia coli. Our analysis of 586 ampR clones represents a high-resolution snapshot of plasmid forms present in the transformed yeast cells with a detection limit of structural changes of <2%. Altered forms summed up to about 11%, constituting likely a lower limit. We have observed two categories of recombination events. One is Flp based, with products of intermolecular recombination with the 2 μm, likely intermediates that are prerequisites for YEp-type plasmid amplification. The other type is based on Flp-independent homologous recombination leading to oligomerization of such plasmids also in a 2μm-free [cir°] strain, i.e. in the absence of Flp. Beyond the general maintenance and its functional sequences, only the gene of interest and its expression might have an impact on the physiology of the host.
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Affiliation(s)
- Ruben Hohnholz
- Department of Industrial Microbiology, City University of Applied Sciences Bremen, Neustadtswall 30, D-28199 Bremen, Germany
| | - Tilman Achstetter
- Department of Industrial Microbiology, City University of Applied Sciences Bremen, Neustadtswall 30, D-28199 Bremen, Germany
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Sau S, Ghosh SK, Liu YT, Ma CH, Jayaram M. Hitchhiking on chromosomes: A persistence strategy shared by diverse selfish DNA elements. Plasmid 2019; 102:19-28. [PMID: 30726706 DOI: 10.1016/j.plasmid.2019.01.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 01/29/2019] [Accepted: 01/31/2019] [Indexed: 12/12/2022]
Abstract
An underlying theme in the segregation of low-copy bacterial plasmids is the assembly of a 'segrosome' by DNA-protein and protein-protein interactions, followed by energy-driven directed movement. Analogous partitioning mechanisms drive the segregation of host chromosomes as well. Eukaryotic extra-chromosomal elements, exemplified by budding yeast plasmids and episomes of certain mammalian viruses, harbor partitioning systems that promote their physical association with chromosomes. In doing so, they indirectly take advantage of the spindle force that directs chromosome movement to opposite cell poles. Molecular-genetic, biochemical and cell biological studies have revealed several unsuspected aspects of 'chromosome hitchhiking' by the yeast 2-micron plasmid, including the ability of plasmid sisters to associate symmetrically with sister chromatids. As a result, the plasmid overcomes the 'mother bias' experienced by plasmids lacking a partitioning system, and elevates itself to near chromosome status in equal segregation. Chromosome association for stable propagation, without direct energy expenditure, may also be utilized by a small minority of bacterial plasmids-at least one case has been reported. Given the near perfect accuracy of chromosome segregation, it is not surprising that elements residing in evolutionarily distant host organisms have converged upon the common strategy of gaining passage to daughter cells as passengers on chromosomes.
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Affiliation(s)
- Soumitra Sau
- Amity Institute of Biotechnology, Amity University Kolkata, Kolkata 700135, India
| | - Santanu Kumar Ghosh
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Yen-Ting Liu
- Department of Molecular Biosciences, UT Austin, Austin, TX TX7 8712, USA
| | - Chien-Hui Ma
- Department of Molecular Biosciences, UT Austin, Austin, TX TX7 8712, USA
| | - Makkuni Jayaram
- Department of Molecular Biosciences, UT Austin, Austin, TX TX7 8712, USA.
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Rizvi SMA, Prajapati HK, Ghosh SK. The 2 micron plasmid: a selfish genetic element with an optimized survival strategy within Saccharomyces cerevisiae. Curr Genet 2017; 64:25-42. [PMID: 28597305 DOI: 10.1007/s00294-017-0719-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 05/29/2017] [Accepted: 05/30/2017] [Indexed: 11/27/2022]
Abstract
Since its discovery in the early 70s, the 2 micron plasmid of Saccharomyces cerevisiae continues to intrigue researchers with its high protein-coding capacity and a selfish nature yet high stability, earning it the title of a 'miniaturized selfish genetic element'. It codes for four proteins (Rep1, Rep2, Raf1, and Flp) vital for its own survival and recruits several host factors (RSC2, Cohesin, Cse4, Kip1, Bik1, Bim1, and microtubules) for its faithful segregation during cell division. The plasmid maintains a high-copy number with the help of Flp-mediated recombination. The plasmids organize in the form of clusters that hitch-hike the host chromosomes presumably with the help of the plasmid-encoded Rep proteins and host factors such as microtubules, Kip1 motor, and microtubule-associated proteins Bik1 and Bim1. Although there is no known yeast cell phenotype associated with the 2 micron plasmid, excessive copies of the plasmid are lethal for the cells, warranting a tight control over the plasmid copy number. This control is achieved through a combination of feedback loops involving the 2 micron encoded proteins. Thus, faithful segregation and a concomitant tightly controlled plasmid copy number ensure an optimized benign parasitism of the 2 micron plasmid within budding yeast.
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Affiliation(s)
- Syed Meraj Azhar Rizvi
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Bombay, Powai, Mumbai, 400076, India
| | - Hemant Kumar Prajapati
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Bombay, Powai, Mumbai, 400076, India
| | - Santanu Kumar Ghosh
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Bombay, Powai, Mumbai, 400076, India.
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