1
|
Higdon AL, Brar GA. Rules are made to be broken: a "simple" model organism reveals the complexity of gene regulation. Curr Genet 2020; 67:49-56. [PMID: 33130938 DOI: 10.1007/s00294-020-01121-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/14/2020] [Accepted: 10/19/2020] [Indexed: 11/27/2022]
Abstract
Global methods for assaying translation have greatly improved our understanding of the protein-coding capacity of the genome. In particular, it is now possible to perform genome-wide and condition-specific identification of translation initiation sites through modified ribosome profiling methods that selectively capture initiating ribosomes. Here we discuss our recent study applying such an approach to meiotic and mitotic timepoints in the simple eukaryote, budding yeast, as an example of the surprising diversity of protein products-many of which are non-canonical-that can be revealed by such methods. We also highlight several key challenges in studying non-canonical protein isoforms that have precluded their prior systematic discovery. A growing body of work supports expanded use of empirical protein-coding region identification, which can help relieve some of the limitations and biases inherent to traditional genome annotation approaches. Our study also argues for the adoption of less static views of gene identity and a broader framework for considering the translational capacity of the genome.
Collapse
Affiliation(s)
- Andrea L Higdon
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA
- Center for Computational Biology, University of California, Berkeley, CA, 94720, USA
| | - Gloria A Brar
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA.
- Center for Computational Biology, University of California, Berkeley, CA, 94720, USA.
| |
Collapse
|
2
|
Eisenberg AR, Higdon AL, Hollerer I, Fields AP, Jungreis I, Diamond PD, Kellis M, Jovanovic M, Brar GA. Translation Initiation Site Profiling Reveals Widespread Synthesis of Non-AUG-Initiated Protein Isoforms in Yeast. Cell Syst 2020; 11:145-160.e5. [PMID: 32710835 PMCID: PMC7508262 DOI: 10.1016/j.cels.2020.06.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/18/2020] [Accepted: 06/24/2020] [Indexed: 12/27/2022]
Abstract
Genomic analyses in budding yeast have helped define the foundational principles of eukaryotic gene expression. However, in the absence of empirical methods for defining coding regions, these analyses have historically excluded specific classes of possible coding regions, such as those initiating at non-AUG start codons. Here, we applied an experimental approach to globally annotate translation initiation sites in yeast and identified 149 genes with alternative N-terminally extended protein isoforms initiating from near-cognate codons upstream of annotated AUG start codons. These isoforms are produced in concert with canonical isoforms and translated with high specificity, resulting from initiation at only a small subset of possible start codons. The non-AUG initiation driving their production is enriched during meiosis and induced by low eIF5A, which is seen in this context. These findings reveal widespread production of non-canonical protein isoforms and unexpected complexity to the rules by which even a simple eukaryotic genome is decoded.
Collapse
Affiliation(s)
- Amy R Eisenberg
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Andrea L Higdon
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Center for Computational Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Ina Hollerer
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Alexander P Fields
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Irwin Jungreis
- MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA 02139, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Paige D Diamond
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Manolis Kellis
- MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA 02139, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Marko Jovanovic
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Gloria A Brar
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Center for Computational Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
| |
Collapse
|
3
|
Luo L, Nishi K, MacLeod E, Sabara MI. Expression and Characterization of HA1 Protein of Highly Pathogenic H5N1 Avian Influenza Virus for Use in a Serodiagnostic Assay. Transbound Emerg Dis 2015; 64:432-441. [PMID: 26040437 DOI: 10.1111/tbed.12382] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Indexed: 11/28/2022]
Abstract
The hemagglutinin ectodomain (HA1 subunit) from highly pathogenic avian influenza (HPAI) isolate (A/chicken/Vietnam/14/2005) was cloned and expressed using a baculovirus expression vector. Biosynthesis, glycosylation and secretion of the HA1 proteins, with natural or a melittin signal peptide at the N-terminus and a six-histidine (6xHis) tag at the C-terminus, were examined in insect cells. A 40-kDa unglycosylated precursor and a fully processed, mature form of the HA1 protein migrated around 52 kDa were detected by SDS-PAGE and confirmed by Western blot using H5N1-specific antibody. Treatment of tunicamycin and peptide-N-glycosidase F (PNGase F) further revealed that the recombinant HA1 proteins produced in insect cells were indeed glycosylated with N-linked oligosaccharide side chains. Time-course experiments showed that substitution of the HA natural sequence with the signal sequence from honeybee melittin promoted a high level of expression and efficient secretion of the HA1. A high yield, 37 μg/ml, of HA1 protein was obtained from recombinant baculovirus-infected cell culture supernatant. In addition, the cell surface expression of rHA1 was detected by indirect immunofluorescent staining and showed biological activity on hemadsorption assays. Recombinant HA1 protein-based ELISA was evaluated and appeared to be sensitive and specific for the rapid detection of H5 subtype-specific antibodies in serum samples. No cross-reactivity to antibodies from 15 other influenza A subtypes was detected. Taken together, the newly developed recombinant HA1-based ELISA could offer an alternative to other diagnostic approaches for the specific detection of H5 avian influenza virus infection.
Collapse
Affiliation(s)
- L Luo
- National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - K Nishi
- National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - E MacLeod
- National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - M I Sabara
- National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| |
Collapse
|
4
|
Dunn JG, Foo CK, Belletier NG, Gavis ER, Weissman JS. Ribosome profiling reveals pervasive and regulated stop codon readthrough in Drosophila melanogaster. eLife 2013; 2:e01179. [PMID: 24302569 PMCID: PMC3840789 DOI: 10.7554/elife.01179] [Citation(s) in RCA: 265] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Ribosomes can read through stop codons in a regulated manner, elongating rather than terminating the nascent peptide. Stop codon readthrough is essential to diverse viruses, and phylogenetically predicted to occur in a few hundred genes in Drosophila melanogaster, but the importance of regulated readthrough in eukaryotes remains largely unexplored. Here, we present a ribosome profiling assay (deep sequencing of ribosome-protected mRNA fragments) for Drosophila melanogaster, and provide the first genome-wide experimental analysis of readthrough. Readthrough is far more pervasive than expected: the vast majority of readthrough events evolved within D. melanogaster and were not predicted phylogenetically. The resulting C-terminal protein extensions show evidence of selection, contain functional subcellular localization signals, and their readthrough is regulated, arguing for their importance. We further demonstrate that readthrough occurs in yeast and humans. Readthrough thus provides general mechanisms both to regulate gene expression and function, and to add plasticity to the proteome during evolution. DOI: http://dx.doi.org/10.7554/eLife.01179.001.
Collapse
Affiliation(s)
- Joshua G Dunn
- California Institute of Quantitative Biosciences, San Francisco, United States
| | | | | | | | | |
Collapse
|
5
|
Palazzo AF, Mahadevan K, Tarnawsky SP. ALREX-elements and introns: two identity elements that promote mRNA nuclear export. WILEY INTERDISCIPLINARY REVIEWS-RNA 2013; 4:523-33. [PMID: 23913896 DOI: 10.1002/wrna.1176] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 04/24/2013] [Accepted: 04/26/2013] [Indexed: 11/09/2022]
Abstract
The mechanisms that dictate whether a particular mRNA is exported from the nucleus are still poorly defined. However, it has become increasingly clear that these mechanisms act to promote the expression of protein-coding mRNAs over the high levels of spurious transcription that is endemic to most eukaryotic genomes. For example, mRNA processing events that are associated with protein-coding transcripts, such as splicing, act as mRNA identity elements that promote nuclear export of these transcripts. Six years ago, we made the serendipitous discovery that regions within the open reading frame of an mRNA that encode short secretory or mitochondrial-targeting peptides can also act as an mRNA identity element which promotes an alternative mRNA nuclear export (ALREX) pathway. These regions are enriched in protein coding genes and have particular features that can be used to identify this class of protein-coding mRNA. In this article we review our current knowledge of how mRNA export evolved in response to particular events that occurred at the base of the eukaryotic tree. We will then focus on our current understanding of ALREX and compare its features to splicing-dependent export, the main mRNA export pathway in metazoans.
Collapse
|
6
|
Mahadevan K, Zhang H, Akef A, Cui XA, Gueroussov S, Cenik C, Roth FP, Palazzo AF. RanBP2/Nup358 potentiates the translation of a subset of mRNAs encoding secretory proteins. PLoS Biol 2013; 11:e1001545. [PMID: 23630457 PMCID: PMC3635865 DOI: 10.1371/journal.pbio.1001545] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 03/07/2013] [Indexed: 12/14/2022] Open
Abstract
After nuclear export, mRNAs encoding secretory proteins interact with RanBP2/Nup358 on the cytoplasmic face of the nuclear pore, a step that is required for the efficient translation of these mRNAs. In higher eukaryotes, most mRNAs that encode secreted or membrane-bound proteins contain elements that promote an alternative mRNA nuclear export (ALREX) pathway. Here we report that ALREX-promoting elements also potentiate translation in the presence of upstream nuclear factors. These RNA elements interact directly with, and likely co-evolved with, the zinc finger repeats of RanBP2/Nup358, which is present on the cytoplasmic face of the nuclear pore. Finally we show that RanBP2/Nup358 is not only required for the stimulation of translation by ALREX-promoting elements, but is also required for the efficient global synthesis of proteins targeted to the endoplasmic reticulum (ER) and likely the mitochondria. Thus upon the completion of export, mRNAs containing ALREX-elements likely interact with RanBP2/Nup358, and this step is required for the efficient translation of these mRNAs in the cytoplasm. ALREX-elements thus act as nucleotide platforms to coordinate various steps of post-transcriptional regulation for the majority of mRNAs that encode secreted proteins. About one-fifth of the protein-coding genes in the human genome code for secreted and/or membrane-bound proteins. In the nucleus these genes are transcribed into messenger RNAs (mRNAs), which are then exported to the cytoplasm. These mRNAs are then transported to the surface of the endoplasmic reticulum where they are translated into proteins destined for the secretory pathway. Most of these mRNAs contain signal sequence coding regions (SSCRs), which code for short hydrophobic polypeptides that target the newly synthesized proteins for translocation across the endoplasmic reticulum membrane. Previously, we found that many SSCRs also act as RNA elements that promote the efficient nuclear export of mRNAs. Here we present evidence that upon the completion of nuclear export, SSCR-containing mRNAs interact with RanBP2/Nup358, a large protein found on the cytoplasmic face of the nuclear pore. This interaction is mediated by direct binding between the SSCR and zinc finger repeats found within RanBP2/Nup358, and is ultimately required for the efficient translation of SSCR-containing mRNAs into secretory and/or membrane-bound proteins. Our work demonstrates that SSCRs act as nucleotide platforms that recruit various factors to the mRNA throughout its life to regulate distinct events, such as nuclear export and translation.
Collapse
Affiliation(s)
- Kohila Mahadevan
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Hui Zhang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Abdalla Akef
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Xianying A. Cui
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Serge Gueroussov
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Can Cenik
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Department of Biochemistry and Molecular Pharmacology University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Frederick P. Roth
- Department of Biological Chemistry & Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
- Samuel Lunenfeld Research Institute, Mt. Sinai Hospital, Toronto, Ontario, Canada
| | - Alexander F. Palazzo
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
| |
Collapse
|
7
|
Tartakoff AM, Tao T. Comparative and evolutionary aspects of macromolecular translocation across membranes. Int J Biochem Cell Biol 2009; 42:214-29. [PMID: 19643202 DOI: 10.1016/j.biocel.2009.07.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/21/2009] [Accepted: 07/21/2009] [Indexed: 01/10/2023]
Abstract
Membrane barriers preserve the integrity of organelles of eukaryotic cells, yet the genesis and ongoing functions of the same organelles requires that their limiting membranes allow import and export of selected macromolecules. Multiple distinct mechanisms are used for this purpose, only some of which have been traced to prokaryotes. Some can accommodate both monomeric and also large heterooligomeric cargoes. The best characterized of these is nucleocytoplasmic transport. This synthesis compares the unidirectional and bidirectional mechanisms of macromolecular transport of the endoplasmic reticulum, mitochondria, peroxisomes and the nucleus, calls attention to the powerful experimental approaches which have been used for their elucidation, discusses their regulation and evolutionary origins, and highlights relatively unexplored areas.
Collapse
Affiliation(s)
- Alan M Tartakoff
- Department of Pathology & Cell Biology Program, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
| | | |
Collapse
|
8
|
Karniely S, Rayzner A, Sass E, Pines O. Alpha-complementation as a probe for dual localization of mitochondrial proteins. Exp Cell Res 2006; 312:3835-46. [PMID: 17034789 DOI: 10.1016/j.yexcr.2006.08.021] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 08/12/2006] [Accepted: 08/15/2006] [Indexed: 11/23/2022]
Abstract
There are a growing number of proteins which are reported to reside in multiple compartments within the eukaryotic cell. However, lack of appropriate methods limits our knowledge on the true extent of this phenomenon. In this study, we demonstrate a novel application of beta-galactosidase alpha-complementation to study dual distribution of proteins in yeast cells. Using a simple colony color phenotype, we show that alpha-complementation depends on co-compartmentalization of alpha and omega fragments and exploit this to probe dual localization of proteins between the cytosol and mitochondria in yeast. The quality of our assay was assessed by analysis of the known dual targeted enzyme fumarase and several mutant derivatives, which are exclusively localized to one or the other of these subcellular compartments. Addition of the alpha fragment did not abolish the enzymatic activity of the tagged proteins nor did it affect their localization. By examining 10 yeast gene products for distribution between the cytosol and the mitochondria, we demonstrate the potential of alpha-complementation to screen the mitochondrial proteome for dual distribution. Our data indicate the distribution of two uncharacterized proteins--Bna3 and Nif3--between the cytosol and the mitochondria.
Collapse
Affiliation(s)
- Sharon Karniely
- Department of Molecular Biology, Hebrew University Medical School, Jerusalem 91120, Israel
| | | | | | | |
Collapse
|
9
|
Dalton JP, Brindley PJ, Knox DP, Brady CP, Hotez PJ, Donnelly S, O'Neill SM, Mulcahy G, Loukas A. Helminth vaccines: from mining genomic information for vaccine targets to systems used for protein expression. Int J Parasitol 2003; 33:621-40. [PMID: 12782060 DOI: 10.1016/s0020-7519(03)00057-2] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The control of helminth diseases of people and livestock continues to rely on the widespread use of anti-helminthic drugs. However, concerns with the appearance of drug resistant parasites and the presence of pesticide residues in food and the environment, has given further incentive to the goal of discovering molecular vaccines against these pathogens. The exponential rate at which gene and protein sequence information is accruing for many helminth parasites requires new methods for the assimilation and analysis of the data and for the identification of molecules capable of inducing immunological protection. Some promising vaccine candidates have been discovered, in particular cathepsin L proteases from Fasciola hepatica, aminopeptidases from Haemonchus contortus, and aspartic proteases from schistosomes and hookworms, all of which are secreted into the host tissues or into the parasite intestine where they play important roles in host-parasite interactions. Since secreted proteins, in general, are exposed to the immune system of the host they represent obvious candidates at which vaccines could be targeted. Therefore, in this article, we consider the potential values and uses of algorithms for characterising cDNAs amongst the collated helminth genomic information that encode secreted proteins, and methods for their selective isolation and cloning. We also review the variety of prokaryotic and eukaryotic cell expression systems that have been employed for the production and downstream purification of recombinant proteins in functionally active form, and provide an overview of the parameters that must be considered if these recombinant proteins are to be commercialised as vaccine therapeutics in humans and/or animals.
Collapse
Affiliation(s)
- John P Dalton
- School of Biotechnology, Dublin City University, Glasnevin, Dublin 9, Ireland.
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Darsow T, Odorizzi G, Emr SD. Invertase fusion proteins for analysis of protein trafficking in yeast. Methods Enzymol 2001; 327:95-106. [PMID: 11044977 DOI: 10.1016/s0076-6879(00)27270-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- T Darsow
- Department of Biology, University of California, San Diego, La Jolla 92093-0668, USA
| | | | | |
Collapse
|
11
|
Jeffery CJ, Koshland DE. The Escherichia coli aspartate receptor: sequence specificity of a transmembrane helix studied by hydrophobic-biased random mutagenesis. PROTEIN ENGINEERING 1999; 12:863-72. [PMID: 10556247 DOI: 10.1093/protein/12.10.863] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The Escherichia coli aspartate receptor is a dimer with two transmembrane sequences per monomer that connect a periplasmic ligand binding domain to a cytoplasmic signaling domain. The method of 'hydrophobic-biased' random mutagenesis, that we describe here, was used to construct mutant aspartate receptors in which either the entire transmembrane sequence or seven residues near the center of the transmembrane sequence were replaced with hydrophobic and polar random residues. Some of these receptors responded to aspartate in an in vivo chemotaxis assay, while others did not. The acceptable substitutions included hydrophobic to polar residues, small to larger residues, and large to smaller residues. However, one mutant receptor that had only a few hydrophobic substitutions did not respond to aspartate. These results add to our understanding of sequence specificity in the transmembrane regions of proteins with more than one transmembrane sequence. This work also demonstrates a method of constructing families of mutant proteins containing random residues with chosen characteristics.
Collapse
Affiliation(s)
- C J Jeffery
- Department of Molecular and Cell Biology, 329 Stanley Hall, University of California, Berkeley, CA 94720, USA
| | | |
Collapse
|
12
|
Abstract
Protein sorting signals provide good examples of peptides that can be studied both from a chemical and a biochemical perspective. Their simple designs and low degree of sequence conservation suggest that they are involved in rather non-specific peptide-lipid interactions, yet their ability to discriminate efficiently between the import machineries of different subcellular compartments rather points to the importance of peptide-receptor interactions. The study of protein sorting signals thus invites a cross-disciplinary approach.
Collapse
Affiliation(s)
- G von Heijne
- Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden
| |
Collapse
|
13
|
Abstract
We have developed assays using cells and isolated membranes to identify factors mediating fusion of the ER-nuclear membrane network in yeast. When cells containing distinctly tagged ER-nuclear envelope membranes are observed during mating, the markers of both parental membranes become colocalized in a process sharing a genetic requirement with karyogamy. Using isolated membranes, we find that fusion between ER compartments requires ATP, but not cytosol, Sec17p (alpha-SNAP), or Sec18p (NSF), the latter two being required at the fusion step in vesicular transport. Proteins tightly associated with the ER membrane are essential for fusion, as is Kar2p (BiP), an ER lumenal hsp70 homolog. BiP may activate an ER-localized fusogen, allowing nuclear fusion and karyogamy in yeast.
Collapse
Affiliation(s)
- M Latterich
- Howard Hughes Medical Institute, University of California, Berkeley 94720
| | | |
Collapse
|
14
|
Larriba G. Translocation of proteins across the membrane of the endoplasmic reticulum: a place for Saccharomyces cerevisiae. Yeast 1993; 9:441-63. [PMID: 8391742 DOI: 10.1002/yea.320090502] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Affiliation(s)
- G Larriba
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| |
Collapse
|
15
|
Preuss D, Mulholland J, Kaiser CA, Orlean P, Albright C, Rose MD, Robbins PW, Botstein D. Structure of the yeast endoplasmic reticulum: localization of ER proteins using immunofluorescence and immunoelectron microscopy. Yeast 1991; 7:891-911. [PMID: 1803815 DOI: 10.1002/yea.320070902] [Citation(s) in RCA: 152] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The endoplasmic reticulum (ER) and other secretory compartments of Saccharomyces cerevisiae have biochemical functions that closely parallel those described in higher eukaryotic cells, yet the morphology of the yeast organelles is quite distinct. In order to associate ER functions with the corresponding cellular structures, we localized several proteins, each of which is expected to be associated with the ER on the basis of enzymatic activity, biological function, or oligosaccharide content. These marker proteins were visualized by immunofluorescence or immunoelectron microscopy, allowing definition of the S. cerevisiae ER structure, both in intact cells and at the ultrastructural level. Each marker protein was most abundant within the membranes that envelop the nucleus and several were also found in extensions of the ER that frequently juxtapose the plasma membrane. Double-labeling experiments were entirely consistent with the idea that the marker proteins reside within the same compartment. This analysis has permitted, for the first time, a detailed characterization of the ER morphology as yeast cells proceed through their growth and division cycles.
Collapse
Affiliation(s)
- D Preuss
- Department of Genetics, Stanford University Medical Center, CA 94305
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Tessier DC, Thomas DY, Khouri HE, Laliberté F, Vernet T. Enhanced secretion from insect cells of a foreign protein fused to the honeybee melittin signal peptide. Gene 1991; 98:177-83. [PMID: 2016060 DOI: 10.1016/0378-1119(91)90171-7] [Citation(s) in RCA: 217] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The baculovirus/insect cell system has been remarkably successful in yielding high levels of synthesis of many proteins which have been difficult to synthesize in other host/vector systems. The system is also capable of secreting heterologous proteins, but with generally low efficiency. We have increased the efficiency of secretion of the system by using signal peptides of insect origin to direct the secretion of a foreign protein. The precursor of the plant cysteine protease papain (propapain) has been used as a report enzyme to compare secretion efficiency. Insect cells infected with a baculovirus recombined with the gene encoding propapain fused to the sequence encoding the honeybee melittin signal peptide secreted over five times more papain precursor than the wild-type prepropapain which used the plant signal peptide. Based on these results, we have assembled pVT-Bac, an Autographa californica nuclear polyhedrosis virus transfer vector that may enhance secretion of other foreign proteins from insect cells. The vector incorporates a number of features: phage f1 ori to facilitate site-directed mutagenesis, the strong polyhedrin promoter upstream from the melittin signal peptide-encoding sequence, and eight unique restriction sites to facilitate fusion of heterologous genes.
Collapse
Affiliation(s)
- D C Tessier
- Genetic Engineering Section, National Research Council of Canada, Montréal Québec
| | | | | | | | | |
Collapse
|
17
|
|