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Cheaib M, Dehghani Amirabad A, Nordström KJV, Schulz MH, Simon M. Epigenetic regulation of serotype expression antagonizes transcriptome dynamics in Paramecium tetraurelia. DNA Res 2015; 22:293-305. [PMID: 26231545 PMCID: PMC4535620 DOI: 10.1093/dnares/dsv014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 06/28/2015] [Indexed: 12/31/2022] Open
Abstract
Phenotypic variation of a single genotype is achieved by alterations in gene expression patterns. Regulation of such alterations depends on their time scale, where short-time adaptations differ from permanently established gene expression patterns maintained by epigenetic mechanisms. In the ciliate Paramecium, serotypes were described for an epigenetically controlled gene expression pattern of an individual multigene family. Paradoxically, individual serotypes can be triggered in Paramecium by alternating environments but are then stabilized by epigenetic mechanisms, thus raising the question to which extend their expression follows environmental stimuli. To characterize environmental adaptation in the context of epigenetically controlled serotype expression, we used RNA-seq to characterize transcriptomes of serotype pure cultures. The resulting vegetative transcriptome resource is first analysed for genes involved in the adaptive response to the altered environment. Secondly, we identified groups of genes that do not follow the adaptive response but show co-regulation with the epigenetically controlled serotype system, suggesting that their gene expression pattern becomes manifested by similar mechanisms. In our experimental set-up, serotype expression and the entire group of co-regulated genes were stable among environmental changes and only heat-shock genes altered expression of these gene groups. The data suggest that the maintenance of these gene expression patterns in a lineage represents epigenetically controlled robustness counteracting short-time adaptation processes.
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Affiliation(s)
- Miriam Cheaib
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany
| | - Azim Dehghani Amirabad
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany Cluster of Excellence for Multimodal Computing and Interaction, Saarland University and Max Planck Institute for Informatics, Saarbrücken 66123, Germany
| | - Karl J V Nordström
- Epigenetics Department, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany
| | - Marcel H Schulz
- Cluster of Excellence for Multimodal Computing and Interaction, Saarland University and Max Planck Institute for Informatics, Saarbrücken 66123, Germany
| | - Martin Simon
- Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, Saarbrücken 66123, Germany
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2
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Ponsuwanna P, Kümpornsin K, Chookajorn T. Genome-wide prediction of the polymorphic Ser gene family in Tetrahymena thermophila based on motif analysis. PLoS One 2014; 9:e105201. [PMID: 25133747 PMCID: PMC4136848 DOI: 10.1371/journal.pone.0105201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 07/21/2014] [Indexed: 11/18/2022] Open
Abstract
Even though antigenic variation is employed among parasitic protozoa for host immune evasion, Tetrahymena thermophila, a free-living ciliate, can also change its surface protein antigens. These cysteine-rich glycosylphosphatidylinositol (GPI)-linked surface proteins are encoded by a family of polymorphic Ser genes. Despite the availability of T. thermophila genome, a comprehensive analysis of the Ser family is limited by its high degree of polymorphism. In order to overcome this problem, a new approach was adopted by searching for Ser candidates with common motif sequences, namely length-specific repetitive cysteine pattern and GPI anchor site. The candidate genes were phylogenetically compared with the previously identified Ser genes and classified into subtypes. Ser candidates were often found to be located as tandem arrays of the same subtypes on several chromosomal scaffolds. Certain Ser candidates located in the same chromosomal arrays were transcriptionally expressed at specific T. thermophila developmental stages. These Ser candidates selected by the motif analysis approach can form the foundation for a systematic identification of the entire Ser gene family, which will contribute to the understanding of their function and the basis of T. thermophila antigenic variation.
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Affiliation(s)
- Patrath Ponsuwanna
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Krittikorn Kümpornsin
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Thanat Chookajorn
- Center of Excellence in Malaria, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- * E-mail:
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3
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Arslanyolu M, Yıldız MT. Cloning, expression and characterization of a gene encoding mitogen activated protein kinase 2 (MPK2) from Tetrahymena thermophila. Gene 2014; 546:40-9. [PMID: 24858074 DOI: 10.1016/j.gene.2014.05.041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 05/13/2014] [Accepted: 05/20/2014] [Indexed: 10/25/2022]
Abstract
Environmental effects and mitogens determine cell phenotype in eukaryotes mainly through MAPK pathways. However, MAPK signaling pathways in T. thermophila have not been studied comprehensively. This study aims to express recombinant MPK2, a MAPK from T. thermophila, in E. coli to characterize its kinase activity. MPK2 was cloned by RT-PCR using degenerate oligonucleotide primers and RACE method. The full-length cDNA of the MPK2 gene is 1705bp that includes 1281bp ORF coding for a putative protein of 426 amino acids having a mass of 50.2kDa. The putative MPK2 protein contains all eleven conserved subdomains that are characteristics of serine/threonine protein kinases, and a TDY motif, which is a putative dual phosphorylation site common in Protista. MPK2 displays highest 48% overall identity to human ERK5 (MAPK7). The expression vector pGEX4T-1-MPK2 was constructed by inserting the coding region of MPK2 cDNA into pGEX4T-1 after introducing the nine point mutations, and then transformed into E. coli BL21(DE3). Autophosphorylation of 76kDa GST-MPK2 at tyrosine residues was confirmed not only by Western blot using anti-phosphotyrosine monoclonal antibody but also by in vitro kinase assay. GST-MPK2 was also able to phosphorylate the artificial substrate myelin basic protein. This study concludes that the free-living unicellular protist T. thermophila MPK2 has commonly conserved MAPK enzyme features, possibly involved in the regulation of cell survival responding to abiotic or biotic stressors, and the production and movement of haploid gametic nuclei between pairs during conjugation.
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Affiliation(s)
- Muhittin Arslanyolu
- Anadolu University, Faculty of Sciences, Department of Biology, Yunusemre Campus, 26470 Eskisehir Turkey.
| | - Mehmet Taha Yıldız
- Fatih University, Faculty of Sciences, Department of Biology, Buyukcekmece Campus, 34500 Istanbul, Turkey.
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4
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Qian Z, Meng B, Wang Q, Wang Z, Zhou C, Wang Q, Tu S, Lin L, Ma Y, Liu S. Systematic characterization of a novel gal operon in Thermoanaerobacter tengcongensis. MICROBIOLOGY-SGM 2009; 155:1717-1725. [PMID: 19372161 DOI: 10.1099/mic.0.025536-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
On the basis of the Thermoanaerobacter tengcongensis genome, a novel type of gal operon was deduced. The gene expression and biochemical properties of this operon were further characterized. RT-PCR analysis of the intergenic regions suggested that the transcription of the gal operon was continuous. With gene cloning and enzyme activity assays, TTE1929, TTE1928 and TTE1927 were identified to be GalT, GalK and GalE, respectively. Results elicited from polarimetry assays revealed that TTE1925, a hypothetical protein, was a novel mutarotase, termed MR-Tt. TTE1926 was identified as a regulator that could bind to two operators in the operon promoter. The transcriptional start sites were mapped, and this suggested that there are two promoters in this operon. Expression of the gal genes was significantly induced by galactose, whereas only MR-Tt expression was detected in glucose-cultured T. tengcongensis at both the mRNA and the protein level. In addition, the abundance of gal proteins was examined at different temperatures. At temperatures ranging from 60 to 80 degrees C, the level of MR-Tt protein was relatively stable, but that of the other gal proteins was dramatically decreased. The operator-binding complexes were isolated and identified by electrophoretic mobility shift assay-liquid chromatography (EMSA-LC) MS-MS, which suggested that several regulatory proteins, such as GalR and a sensory histidine kinase, participate in the regulation of the gal operon.
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Affiliation(s)
- Zhong Qian
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Bo Meng
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Quanhui Wang
- Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, PR China
| | - Zhuowei Wang
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Chuanqi Zhou
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Qian Wang
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Shuyang Tu
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Liang Lin
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
| | - Yanhe Ma
- Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, PR China
| | - Siqi Liu
- Beijing Proteomics Institute, Beijing 101318, PR China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 101318, PR China
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5
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Abstract
In the past decades, the major focus of antigen variation research has been on parasitic protists. However, antigenic variation occurs also in free-living protists. The antigenic systems of the ciliates Paramecium and Tetrahymena have been studied for more than 100 yr. In spite of different life strategies and distant phylogenetic relationships of free-living ciliates and parasitic protists, their antigenic systems have features in common, such as the presence of repeated protein motifs and multigene families. The function of variable surface antigens in free-living ciliates is still unknown. Up to now no detailed monitoring of antigen expression in free-living ciliates in natural habitats has been performed. Unlike stochastic switching in parasites, antigen expression in ciliates can be directed, e.g. by temperature, which holds great advantages for research on the expression mechanism. Regulated expression of surface antigens occurs in an exclusive way and the responsible mechanism is complex, involving both transcriptional and post-transcriptional features. The involvement of homology-dependent effects has been proposed several times but has not been proved yet.
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Affiliation(s)
- Martin C Simon
- Department of Ecology, University of Kaiserslautern, Building 14, Gottlieb-Daimler-Street, 67663 Kaiserslautern, Germany.
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Shiurba R, Hirabayashi T, Masuda M, Kawamura A, Komoike Y, Klitz W, Kinowaki K, Funatsu T, Kondo S, Kiyokawa S, Sugai T, Kawamura K, Namiki H, Higashinakagawa T. Cellular responses of the ciliate, Tetrahymena thermophila, to far infrared irradiation. Photochem Photobiol Sci 2006; 5:799-807. [PMID: 17047831 DOI: 10.1039/b601741j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Infrared rays from sunlight permeate the earth's atmosphere, yet little is known about their interactions with living organisms. To learn whether they affect cell structure and function, we tested the ciliated protozoan, Tetrahymena thermophila. These unicellular eukaryotes aggregate in swarms near the surface of freshwater habitats, where direct and diffuse solar radiation impinge upon the water-air interface. We report that populations irradiated in laboratory cultures grew and mated normally, but major changes occurred in cell physiology during the stationary phase. Early on, there were significant reductions in chromatin body size and the antibody reactivity of methyl groups on lysine residues 4 and 9 in histone H3. Later, when cells began to starve, messenger RNAs for key proteins related to chromatin structure, intermediary metabolism and cellular motility increased from two- to nearly nine-fold. Metabolic activity, swimming speed and linearity of motion also increased, and spindle shaped cells with a caudal cilium appeared. Our findings suggest that infrared radiation enhances differentiation towards a dispersal cell-like phenotype in saturated populations of Tetrahymena thermophila.
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Affiliation(s)
- Robert Shiurba
- Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
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7
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Dou Y, Bowen J, Liu Y, Gorovsky MA. Phosphorylation and an ATP-dependent process increase the dynamic exchange of H1 in chromatin. J Cell Biol 2002; 158:1161-70. [PMID: 12356861 PMCID: PMC2173238 DOI: 10.1083/jcb.200202131] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In Tetrahymena cells, phosphorylation of linker histone H1 regulates transcription of specific genes. Phosphorylation acts by creating a localized negative charge patch and phenocopies the loss of H1 from chromatin, suggesting that it affects transcription by regulating the dissociation of H1 from chromatin. To test this hypothesis, we used FRAP of GFP-tagged H1 to analyze the effects of mutations that either eliminate or mimic phosphorylation on the binding of H1 to chromatin both in vivo and in vitro. We demonstrate that phosphorylation can increase the rate of dissociation of H1 from chromatin, providing a mechanism by which it can affect H1 function in vivo. We also demonstrate a previously undescribed ATP-dependent process that has a global effect on the dynamic binding of linker histone to chromatin.
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Affiliation(s)
- Yali Dou
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
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8
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Gerber CA, Lopez AB, Shook SJ, Doerder FP. Polymorphism and selection at the SerH immobilization antigen locus in natural populations of Tetrahymena thermophila. Genetics 2002; 160:1469-79. [PMID: 11973302 PMCID: PMC1462060 DOI: 10.1093/genetics/160.4.1469] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The SerH locus of Tetrahymena thermophila is one of several paralogous loci with genes encoding variants of the major cell surface protein known as the immobilization antigen (i-ag). The locus is highly polymorphic, raising questions concerning functional equivalency and selective forces acting on its multiple alleles. Here, we compare the sequences and expression of SerH1, SerH3, SerH4, SerH5, and SerH6. The precursor i-ags are highly similar. They are rich in alanine, serine, threonine, and cysteine and they share nearly identical ER translocation and GPI addition signals. The locations of the 39 cysteines are highly conserved, particularly in the 3.5 central, imperfect tandem repeats in which 8 periodic cysteines punctuate alternating short and long stretches of amino acids. Hydrophobicity patterns are also conserved. Nevertheless, amino acid sequence identity is low, ranging from 60.7 to 82.9%. At the nucleotide level, from 9.7 to 26.7% of nucleotide sites are polymorphic in pairwise comparisons. Expression of each allele is regulated by temperature-sensitive mRNA stability. H mRNAs are stable at <36 degrees but are unstable at >36 degrees. The H5 mRNA, which is less affected by temperature, has a different arrangement of the putative mRNA destabilization motif AUUUA. Statistical analysis of SerH genes indicates that the multiple alleles are neutral. Significantly low ratios of the rates of nonsynonymous to synonymous amino acid substitutions suggest that the multiple alleles are subject to purifying (negative) selection enforcing constraints on structure.
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Affiliation(s)
- Carri A Gerber
- Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio 44115, USA
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9
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Doerder FP, Gerber CA. Molecular characterization of the SerL paralogs of Tetrahymena thermophila. Biochem Biophys Res Commun 2000; 278:621-6. [PMID: 11095959 DOI: 10.1006/bbrc.2000.3857] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the pond ciliate Tetrahymena thermophila, expression of genes encoding variant forms of the cell surface immobilization antigen (i-ag) is regulated by environmental conditions. Multiple isoforms of the L i-ags are found on the surface of cells grown at <20 degrees C as well as on the surface of rseC mutants which express SerL genes constitutively. Five cDNAs encoding variant L i-ags of rseC were sequenced and their expression studied. Two additional SerL genes from natural isolates were sequenced. Members of the SerL family encode polypeptides with 148, 316, or 371 amino acids, and the i-ags have two, five, or six imperfect repeats, respectively, flanked by putative ER translocation and GPI addition signals. Each repeat contains six periodic cysteines, in contrast to eight or ten in other i-ags of T. thermophila. At least three of the five genes constitutively expressed in rseC mutants are differentially expressed in cells expressing other i-ags. Northern analysis and RT-PCR indicate that expression of some members of the SerL family is regulated by both transcription and mRNA stability while another member is regulated primarily by mRNA stability.
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Affiliation(s)
- F P Doerder
- Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, Ohio, 44115, USA.
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10
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Doerder FP. Sequence and expression of the SerJ immobilization antigen gene of Tetrahymena thermophila regulated by dominant epistasis. Gene 2000; 257:319-26. [PMID: 11080598 DOI: 10.1016/s0378-1119(00)00380-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In ciliates, variable surface protein genes encoding the immobilization antigen (-ag) are expressed under different environmental conditions, including temperature and salt stress. These i-ags are GPI-linked and coat the entire external surface of the cell, including the cilia. In Tetrahymena thermophila-ag in natural isolates is the result of dominant epistasis masking the expression of the H i-ag ordinarily expressed at 20-36 degrees C. This report describes the expression and sequence of the Ser-ag. J is present on the cell surface up to 38 degrees C; above 38 degrees C SerSeranked by an A-rich 5' UTR and a 3' UTR containing putative mRNA destabilization motifs. The encoded J polypeptide consists of 438 amino acids and is rich in alanine, cysteine, serine and threonine. The N- and resemble signal peptide and GPI-anchor addition sites, respectively. The majority of the molecule consists of four imperfect repeats with 10 periodic cysteines per repeat in the pattern CX(6)CX(2)CX(21)CX(4)CX(13-15)CX(2)CX(18)CX(3)CX(11)CX(9-10). Although H i-ags encoded by paralogous SerH genes have 3.5 imperfect repeats with eight periodic cysteines per repeat, J nevertheless resembles H with respect to amino acid composition, codon usage, N- and C-termini, the arrangement of the cysteine periods, and regulation by mRNA stability. However, despite these similarities and epistasis, the evolutionary relationship between SerH and SerJ is unclear.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Antigens, Protozoan
- Antigens, Surface/chemistry
- Antigens, Surface/genetics
- Base Sequence
- Blotting, Northern
- Cysteine/genetics
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Complementary/isolation & purification
- DNA, Protozoan/chemistry
- DNA, Protozoan/genetics
- Epistasis, Genetic
- Gene Expression Regulation
- Molecular Sequence Data
- Protozoan Proteins
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Repetitive Sequences, Amino Acid/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Temperature
- Tetrahymena thermophila/genetics
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Affiliation(s)
- F P Doerder
- Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, USA.
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11
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Affiliation(s)
- K M Karrer
- Department of Biology, Marquette University, Milwaukee, Wisconsin 53201, USA
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12
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Svärd SG, Meng TC, Hetsko ML, McCaffery JM, Gillin FD. Differentiation-associated surface antigen variation in the ancient eukaryote Giardia lamblia. Mol Microbiol 1998; 30:979-89. [PMID: 9988475 DOI: 10.1046/j.1365-2958.1998.01125.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Encystation of Giardia lamblia is required for survival outside the host, whereas excystation initiates infection. The dormant cyst was considered an adaptation to external survival and passage through the stomach. However, we found previously that trophozoites which had recovered after completion of the life cycle had switched their major variant surface protein (VSP), called TSA 417, but neither the timing nor the molecular mechanism of switching had been elucidated. Here we demonstrate that TSA 417 predominates in cysts, but is downregulated during the stage of excystation that models cyst arrival in the small intestine. Transcripts of new VSPs appear late in encystation, and during and after excystation. Trophozoites appear to prepare for switching during encystation, when the major VSP on the cell surface diminishes and is internalized in lysosome-like vacuoles. As short-range DNA rearrangements were not detected, giardial VSP switching during differentiation appears to resemble the in situ switching of surface glycoproteins in African trypanosomes. We also report a unique extended 15 nucleotide polyadenylation signal in all VSP transcripts, but not in other known giardial genes. Antigenic variation during encystation-excystation may be a novel form of immune evasion that could help explain the common occurrence of reinfection by Giardia and other parasites with similar life cycles.
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Affiliation(s)
- S G Svärd
- Department of Pathology, University of California at San Diego, 92103-8416, USA
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13
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Deak JC, Doerder FP. High frequency intragenic recombination during macronuclear development in Tetrahymena thermophila restores the wild-type SerH1 gene. Genetics 1998; 148:1109-15. [PMID: 9539428 PMCID: PMC1460036 DOI: 10.1093/genetics/148.3.1109] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Macronuclear development in ciliates is characterized by extensive rearrangement of genetic material, including sequence elimination, chromosome fragmentation and telomere addition. Intragenic recombination is a relatively rare, but evolutionarily important phenomenon occurring in mitosis and meiosis in a wide variety of organisms. Here, we show that high frequency intragenic recombination, on the order of 30%, occurs in the developing amitotic macronucleus of the ciliate Tetrahymena thermophila. Such recombination, occurring between two nonsense transition mutations separated by 726 nucleotides, reproducibly restores wild-type expression of the SerH1 surface protein gene, thus mimicking complementation in trans heterozygotes. Recombination must be considered a potentially important aspect of macronuclear development, producing gene combinations not present in the germinal micronucleus.
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Affiliation(s)
- J C Deak
- Department of Biology, Cleveland State University, Ohio 44115, USA
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14
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DeMaria CT, Brewer G. Cell-free systems for analysis of cytoplasmic mRNA turnover. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 1997; 18:65-91. [PMID: 8994261 DOI: 10.1007/978-3-642-60471-3_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- C T DeMaria
- Department of Microbiology and Immunology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1064, USA
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15
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Abstract
In a linker histone H1 knockout strain (delta H1) of Tetrahymena thermophila, the number of mature RNAs produced by genes transcribed by pol I and pol III and of most genes transcribed by pol II remains unchanged. However, H1 is required for the normal basal repression of a gene (ngoA) in growing cells but is not required for its activated expression in starved cells. Surprisingly, H1 is required for the activated expression of another gene (CyP) in starved cells but not for its repression in growing cells. Thus, H1 does not have a major effect on global transcription but can act as either a positive or negative gene-specific regulator of transcription in vivo.
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Affiliation(s)
- X Shen
- Department of Biology University of Rochester, New York 14627, USA
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16
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CURTENAZ SOPHIE, BEISSON JANINE. In Situ Hybridization as a Method to Study the Regulation of Gene Expression in Paramecium. J Eukaryot Microbiol 1996. [DOI: 10.1111/j.1550-7408.1996.tb01392.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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17
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Bouck GB, Ngô H. Cortical structure and function in euglenoids with reference to trypanosomes, ciliates, and dinoflagellates. INTERNATIONAL REVIEW OF CYTOLOGY 1996; 169:267-318. [PMID: 8843656 DOI: 10.1016/s0074-7696(08)61988-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The membrane skeletal complex (cortex) of euglenoids generates and maintains cell form. In this review we summarize structural, biochemical, physiological, and molecular studies on the euglenoid membrane skeleton, focusing specifically on four principal components: the plasma membrane, a submembrane layer (epiplasm), cisternae of the endoplasmic reticulum, and microtubules. The data from euglenoids are compared with findings from representative organisms of three other protist groups: the trypanosomes, ciliates, and dinoflagellates. Although there are significant differences in cell form and phylogenetic affinities among these groups, there are also many similarities in the organization and possibly the function of their cortical components. For example, an epiplasmic (membrane skeletal) layer is widely used for adding strength and rigidity to the cell surface. The ER/alveolus/amphiesmal vesicle may function in calcium storage and regulation, and in mediating assembly of surface plates. GPI-linked variable surface antigens are characteristic of both ciliates and the unrelated trypanosomatids. Microtubules are ubiquitous, and cortices in trypanosomes may relay exclusively on microtubules and microtubule-associated proteins for maintaining cell form. Also, in agreement with previous suggestions, there is an apparent preservation of many cortical structures during cell duplication. In three of the four groups there is convincing evidence that part or all of the parental cortex persists during cytokinesis, thereby producing mosaics or chimeras consisting of both inherited and newly synthesized cortical components.
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Affiliation(s)
- G B Bouck
- Department of Biological Sciences (M/C 066), University of Illinois at Chicago 60607, USA
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18
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Gitz DL, Pennock DG. Deciliation induces phosphorylation of a 90-kDa cortical protein in Tetrahymena thermophila. J Eukaryot Microbiol 1995; 42:742-8. [PMID: 8520589 DOI: 10.1111/j.1550-7408.1995.tb01626.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have used the anti-phosphoprotein antibody MPM-2 to examine changes in phosphorylation of cortical proteins during cilia regeneration in Tetrahymena thermophila. Although numerous cortical proteins are phosphorylated in both nondeciliated and deciliated cells, deciliation induces a dramatic increase in the phosphorylation of a 90-kDa cortical protein. The 90-kDa protein remained phosphorylated during cilia regeneration and then gradually became dephosphorylated. The 90-kDa protein was phosphorylated and dephosphorylated normally in Tetrahymena mutants that assemble short cilia, suggesting that achievement of full length is not the signal that triggers dephosphorylation of the 90-kDa protein. When initiation of cilia assembly is blocked, the 90-kDa protein becomes phosphorylated and remains phosphorylated for an extended period of time, suggesting that initiation of cilia elongation triggers eventual dephosphorylation of the 90-kDa protein, regardless of how long the cilia actually become.
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Affiliation(s)
- D L Gitz
- Department of Zoology, Miami University, Oxford, Ohio 45056, USA
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19
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Brandt A, Klein A. Transcription rates and transcript stabilities of macronuclear genes in vegetative Euplotes crassus cells. J Eukaryot Microbiol 1995; 42:691-6. [PMID: 8520583 DOI: 10.1111/j.1550-7408.1995.tb01617.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In hypotrichous ciliates such as Euplotes crassus genes in the transcriptionally active macronucleus are present on individual minichromosomes which occur in gene-specific copy numbers. This different degree of gene amplification can be understood as a means to preset the expression potential of the respective genetic information. In addition, the actual steady state transcript amounts are governed by the transcription rates and transcript stabilities. To establish the relative effects of these three parameters the copy numbers of genes transcribed by the three different polymerases were determined. The transcript levels of growing or starving vegetative cells were then determined, and nuclear run-on assays were performed to determine the transcription rates of the genes in the different nutritional states. A weak correlation between the gene copy numbers and transcription rates was found. The transcripts of genes synthesized by RNA polymerase II exhibited different stabilities upon starvation of the cells, compared to the supposedly stable ribosomal 5S and 26S RNA. Refeeding of the cells after starvation also resulted in a differential response with respect to the accumulation of the transcripts of different genes transcribed by RNA polymerase II, which can be interpreted in the context of the gene functions.
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MESH Headings
- Animals
- Base Sequence
- Biological Evolution
- Conjugation, Genetic
- Conserved Sequence
- DNA Probes
- DNA, Protozoan/genetics
- DNA, Ribosomal/genetics
- Euplotes/genetics
- Euplotes/physiology
- Gene Expression
- Genes, Protozoan
- RNA Polymerase II/metabolism
- RNA, Protozoan/biosynthesis
- RNA, Protozoan/genetics
- RNA, Ribosomal/biosynthesis
- RNA, Ribosomal/genetics
- RNA, Ribosomal, 5S/biosynthesis
- RNA, Ribosomal, 5S/genetics
- Transcription, Genetic
- Tubulin/biosynthesis
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Affiliation(s)
- A Brandt
- Department of Biology, Phillipps-University, Marburg, Germany
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20
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Deak JC, Doerder FP. Sequence, codon usage and cysteine periodicity of the SerH1 gene and in the encoded surface protein of Tetrahymena thermophila. Gene 1995; 164:163-6. [PMID: 7590308 DOI: 10.1016/0378-1119(95)00446-d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The temperature-regulated SerH1 gene coding for an immunodominant surface glycoprotein (i-Ag H1) of Tetrahymena thermophila has been sequenced. The gene is reproducibly rearranged during macronuclear development and steady state mRNA levels are present at < 36 degrees C. The deduced i-Ag H1 amino acid (aa) sequence is rich in Ser, Thr and Cys, and contains three periods each consisting of 85 aa punctuated by eight Cys with the general formula, CX6CX17CX2CX18CX2CX11CX2CX19 (where X = any aa). Such Cys periodicity is common to ciliate i-Ag. Codon usage in Tt, Paramecium primaurelia and P. tetraurelia i-Ag encoding genes is similar, with approx. 80% A+T in the 3' position which is in marked contrast to the approx. 54% 3' A+T in other ciliate genes.
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Affiliation(s)
- J C Deak
- Department of Biology, Cleveland State University, OH 44115, USA
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21
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Abstract
This review concerns how cytoplasmic mRNA half-lives are regulated and how mRNA decay rates influence gene expression. mRNA stability influences gene expression in virtually all organisms, from bacteria to mammals, and the abundance of a particular mRNA can fluctuate manyfold following a change in the mRNA half-life, without any change in transcription. The processes that regulate mRNA half-lives can, in turn, affect how cells grow, differentiate, and respond to their environment. Three major questions are addressed. Which sequences in mRNAs determine their half-lives? Which enzymes degrade mRNAs? Which (trans-acting) factors regulate mRNA stability, and how do they function? The following specific topics are discussed: techniques for measuring eukaryotic mRNA stability and for calculating decay constants, mRNA decay pathways, mRNases, proteins that bind to sequences shared among many mRNAs [like poly(A)- and AU-rich-binding proteins] and proteins that bind to specific mRNAs (like the c-myc coding-region determinant-binding protein), how environmental factors like hormones and growth factors affect mRNA stability, and how translation and mRNA stability are linked. Some perspectives and predictions for future research directions are summarized at the end.
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Affiliation(s)
- J Ross
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706, USA
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22
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Abstract
This review concerns how cytoplasmic mRNA half-lives are regulated and how mRNA decay rates influence gene expression. mRNA stability influences gene expression in virtually all organisms, from bacteria to mammals, and the abundance of a particular mRNA can fluctuate manyfold following a change in the mRNA half-life, without any change in transcription. The processes that regulate mRNA half-lives can, in turn, affect how cells grow, differentiate, and respond to their environment. Three major questions are addressed. Which sequences in mRNAs determine their half-lives? Which enzymes degrade mRNAs? Which (trans-acting) factors regulate mRNA stability, and how do they function? The following specific topics are discussed: techniques for measuring eukaryotic mRNA stability and for calculating decay constants, mRNA decay pathways, mRNases, proteins that bind to sequences shared among many mRNAs [like poly(A)- and AU-rich-binding proteins] and proteins that bind to specific mRNAs (like the c-myc coding-region determinant-binding protein), how environmental factors like hormones and growth factors affect mRNA stability, and how translation and mRNA stability are linked. Some perspectives and predictions for future research directions are summarized at the end.
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Affiliation(s)
- J Ross
- McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706, USA
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23
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A Tetrahymena orthologue of the mouse chaperonin subunit CCT gamma and its coexpression with tubulin during cilia recovery. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)62044-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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24
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LaCrosse GL, Doerder FP. A temperature-sensitive mutation of the temperature-regulated SerH3 i-antigen gene of Tetrahymena thermophila: implications for regulation of mutual exclusion. Genetics 1994; 138:297-301. [PMID: 7828814 PMCID: PMC1206149 DOI: 10.1093/genetics/138.2.297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The Ser genes of Tetrahymena thermophila specify alternative forms of a major cell surface glycoprotein, the immobilization or i-antigen (i-ag). Regulation of i-ag expression assures that at least one i-ag gene is expressed at all times. To learn more about the regulatory system and the possible role of i-ag itself, we studied SerH3-ts1, a temperature-sensitive allele of the temperature-regulated SerH3 gene normally expressed from 20-36 degrees. In homozygotes grown at the nonpermissive temperature (> 32 degrees), H3 is not present on the cell surface, but the gene continues to be transcribed until its 36 degrees cutoff. H3 formed at the permissive temperature is stable at nonpermissive temperatures, indicating that SerH3-ts1 is temperature-sensitive for synthesis rather than function. At nonpermissive temperatures, the S i-ag is expressed in place of H3. This result suggests that normal H protein may play a role in regulating S expression. SerH3-ts1 was isolated following mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Sequencing of SerH3-ts1 revealed a single A --> G transition at nucleotide 473, resulting in the substitution of glycine for aspartate. The affected residue is conserved in the internal repeats comprising the H protein, and the charge difference correlates with changes in electrophoretic mobility of the H3 protein.
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Affiliation(s)
- G L LaCrosse
- Department of Biology, Cleveland State University, Ohio 44115
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25
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Amaral MD, Galego L, Rodrigues-Pousada C. Heat-shock-induced protein synthesis is responsible for the switch-off of hsp70 transcription in Tetrahymena. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1174:133-42. [PMID: 8357830 DOI: 10.1016/0167-4781(93)90107-o] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We had previously described that new RNA synthesis is required for expression of the heat shock protein HSP70. Here, we find that the HSP70 mRNA decreases its levels under stress conditions, heat shock (HS) or arsenite (As), and that its levels start to decline at the same time as maximal HSPs synthesis (including HSP70) occurs. This suggests that regulation of the hsp70 gene is mainly exerted at the transcriptional level. Accumulation of the HSP70 mRNA in cells stressed in presence of cycloheximide (CHX), indicates that (a) protein(s) non-existent before stress, possibly HSP70 itself (which is shown here to be relatively stable), is involved in negatively regulating hsp70 expression. Since degradation of the HSP70 mRNA is also shown to occur in cells heat-shocked under CHX, as seen from decay of its levels upon addition of actinomycin D (AMD), the protein(s) must repress hsp70 expression at the transcriptional level. Other conditions that affect normal protein synthesis, namely the translation inhibitor puromycin and the arginine-analog canavanine (shown here to be stress inducers in Tetrahymena pyriformis), also cause a delay in transcription-arrest of the HSP70 mRNA. Under severe stress conditions of HS (36 degrees C) or As (350 microM), the levels of HSP70 mRNA are higher than under mild stress conditions, however, no significant difference is seen in the pattern of HSP70 mRNA decay.
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Affiliation(s)
- M D Amaral
- Laboratório de Genética Molecular, Instituto Gulbenkian de Ciência, Oeiras, Portugal
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26
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Smith DL, Doerder FP. Exceptions to mutual exclusion among cell surface i-antigens of Tetrahymena thermophila during salt stress and stationary phase. THE JOURNAL OF PROTOZOOLOGY 1992; 39:628-35. [PMID: 1522546 DOI: 10.1111/j.1550-7408.1992.tb04862.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In ciliates, only one of the alternative forms of the immunodominant membrane glycoprotein usually coats the external surface of the cell. Such mutual exclusion is regulated at the pretranslational level by mechanisms that result in the expression of a single protein gene. In the holotrich Tetrahymena thermophila five alternative cell surface immobilization proteins (i-antigens) are expressed under different conditions of temperature (L, H, T) and culture media (I, S). Using polyclonal and monoclonal antibodies to these proteins and a cDNA probe derived from the SerH3 gene, we have reinvestigated expression of i-antigens in media supplemented with 0.2 M NaCl. We find that in addition to S, the H and L antigens are also present on the cell surface. While all three i-antigens may be simultaneously present on the cell surface, the combinations S/L and S/H are more frequent. Compared to cells expressing H and L singly, the level of H3 mRNA is diminished, and a subset of the L family of polypeptides is variably expressed. The expression of S begins within 30 min after transfer to NaCl-supplemented medium, while the expression of L begins three days to several weeks after transfer. When cells are transferred out of NaCl-supplemented medium, S is turned off within 24 h, and L is expressed for at least 1 wk prior to the return of full H expression. Although these differences in kinetics suggest differences in control mechanism(s), the absence of I and T on the surface of NaCl-grown cells suggests that there is also a common regulatory link among H, S and L.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D L Smith
- Department of Biology, Cleveland State University, Ohio 44115
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27
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Lin TL, Dickerson HW. Purification and partial characterization of immobilization antigens from Ichthyophthirius multifiliis. THE JOURNAL OF PROTOZOOLOGY 1992; 39:457-63. [PMID: 1383510 DOI: 10.1111/j.1550-7408.1992.tb04832.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ichthyophthirius multifiliis, a parasitic ciliate of freshwater fishes, was found to have surface antigens (Ag) which elicited immobilizing antibodies (Ab) when injected into rabbits. An effort was made to purify and characterize these Ag (referred to as immobilization Ag) because of their potential role in protective immunity in fishes. Mice immunized with theront cilia were used for production of immobilizing monoclonal antibodies (MAb). Hybridomas were screened by indirect immunofluorescent light microscopy and immobilization of live parasites. Six hybridomas producing immobilizing MAb were cloned. Immobilizing MAb were used to affinity purify Ag solubilized with Triton X-114 and Na deoxycholate. Two membrane protein Ag of approximately 48 and 60 kDa were identified. Immobilizing MAb failed to react with these Ag on Western blots and, conversely, MAb that reacted with the Ag on Western blots did not immobilize live organisms. These results suggest that immobilization required native conformational epitopes which were altered by Western blotting procedures. Individual MAb reactive on Western blots recognized both the 48- and 60-kDa proteins indicating the presence of common epitopes. Affinity purified Ag elicited immobilizing antisera when injected into rabbits, mice, and channel catfish.
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Affiliation(s)
- T L Lin
- Fujian Academy of Agricultural Sciences, People's Republic of China
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28
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Clayton C. Developmental regulation of nuclear gene expression in Trypanosoma brucei. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1992; 43:37-66. [PMID: 1410447 DOI: 10.1016/s0079-6603(08)61043-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- C Clayton
- Zentrum für Molekulare Biologie, Heidelberg, Germany
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29
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Soares H, Cyrne L, Barahona I, Rodrigues-Pousada C. Different patterns of expression of beta-tubulin genes in Tetrahymena pyriformis during reciliation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 197:291-9. [PMID: 1902785 DOI: 10.1111/j.1432-1033.1991.tb15910.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The ciliate Tetrahymena pyriformis contains one alpha-tubulin (alpha TT) and two beta-tubulin (beta TT1 and beta TT2) genes. The specific expression of these genes was investigated by Northern blot hybridization using oligonucleotide probes complementary to beta TT1 and beta TT2 genes and the coding region of the alpha-tubulin gene. The three genes are expressed producing 1.8-kb mRNAs but the level of beta TT1 mRNA is much higher than that of beta TT2 mRNA. During cilia regeneration, we found that the expression patterns of the alpha TT and beta TT1 genes are similar whereas that of the beta TT2 gene is different. The alpha TT and beta TT1 transcripts reached higher values between 60-120 min after the onset of reciliation than in exponentially growing cells, while beta TT2 transcripts were maintained at low levels during the whole period. The differences in the amounts of steady-state populations of the both beta-tubulin mRNAs do not correspond to the copy number per haploid genome. These differences could result from the fact that the promoter region of beta TT2 may contain highly structured sequences which would affect the binding of the respective trans-acting factor(s). The apparent transcription rate revealed a significant increase at 15 min of reciliation which could be responsible for the high levels of alpha TT and beta TT1 transcripts in the cytoplasm between 60-120 min of reciliation. This coordinated response to cilia regeneration of the alpha TT and beta TT1 tubulin genes is also a relevant aspect of our findings. Several conserved motifs found in their promoter regions led us to think that some of them may function as cis-elements in the specific binding of nuclear protein factor(s).
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Affiliation(s)
- H Soares
- Laboratorio de Genetica Molecular, Instituto Gulbenkian de Ciencia, Portugal
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30
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Schulman IG, Wang TT, Stargell LA, Gorovsky MA, Allis CD. Cell-cell interactions trigger the rapid induction of a specific high mobility group-like protein during early stages of conjugation in Tetrahymena. Dev Biol 1991; 143:248-57. [PMID: 1991550 DOI: 10.1016/0012-1606(91)90075-e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Conjugation in Tetrahymena represents an ordered developmental pathway which represents the sexual phase of the ciliate life cycle. This pathway is initiated when starved cells of opposite mating types are mixed and are allowed to make a series of cell-cell contacts (a period termed costimulation) which lead to the formation of mating pairs. Here, we demonstrate that two previously described abundant high mobility group (HMG)-like proteins, HMG B and HMG C, whose synthesis appeared to be coordinately regulated in vegetative cells, are not required during the same stages of conjugation. The level of mRNA for both HMG B and HMG C is high during vegetative growth and during the development of new macronuclei. However, specific induction of HMG B mRNA is observed soon after cells of opposite mating types are mixed. Thus, the genes which encode HMG B and HMG C in Tetrahymena can be controlled independently or coordinately. Nuclear run-on experiments show that a significant factor underlying the rapid induction of HMG B message early in the sexual cycle is an increase in the transcriptional activity of the HMG B gene. Experiments are presented which show that this induction of HMG B message requires protein synthesis and is dependent upon the cell-cell contacts made during costimulation. Essentially all of the HMG B protein, which is newly synthesized during this period, is targeted to parental macronuclei where it serves an as yet undetermined function(s).
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Affiliation(s)
- I G Schulman
- Department of Biology, Syracuse University, New York 13244-1220
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31
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Karrer KM, Stein-Gavens S. Constancy of adenine methylation in Tetrahymena macronuclear DNA. THE JOURNAL OF PROTOZOOLOGY 1990; 37:409-14. [PMID: 2213654 DOI: 10.1111/j.1550-7408.1990.tb01165.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Macronuclear DNA from Tetrahymena was examined in order to determine whether the pattern of adenine methylation changed with the transcriptional activity of nearby genes. The DNA from growing, starved and conjugating cells was digested with six restriction enzymes which are sensitive to methylation of adenine within their recognition site. Southern blots of the restricted DNAs were probed with seven cDNA clones and one genomic clone which are homologous to polyA+ RNAs, whose transcriptional activity varies with the physiological state of the cell. One of the cDNA clones, BC11, had not been described previously. It hybridized to a 1.3 kb transcript which was present in populations of starved and conjugating, but not in growing cells. On Southern blots of genomic DNA it hybridized to a complex pattern of bands which was highly polymorphic between the DNAs of closely related strains. It was estimated that between 137 and 272 sites were assayed for changes in methylation, including at least 27 sites which were known to be methylated. No differences were seen in the size of restriction fragments from cells in different physiological states. The data suggested that the methylation pattern, which is determined during macronuclear development, does not vary with the physiological state of the cell.
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Affiliation(s)
- K M Karrer
- Department of Biology, Marquette University, Milwaukee, Wisconsin 53233
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32
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Affiliation(s)
- A J Brown
- Biotechnology Unit, Institute of Genetics, University of Glasgow, U.K
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33
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Affiliation(s)
- J R Preer
- Department of Biology, Indiana University, Bloomington 47405
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34
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Tondravi MM. DNA rearrangements associated with the H3 surface antigen gene of Tetrahymena thermophila that occur during macronuclear development. Curr Genet 1988; 14:617-26. [PMID: 2854007 DOI: 10.1007/bf00434088] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The surfaces of Tetrahymena thermophila cells grown between 20 and 35 degrees C are covered by one or more variants of H antigens. A cDNA clone, pC6, has previously been identified that hybridizes to a unique polyA+ RNA that appears to code for the SerH3 variant of the H antigens. pC6 and a subclone of it, pGpC6.295, were used to analyze the genomic organization of the corresponding gene(s) in both the macronucleus and the micronucleus. It was determined that pC6 hybridizes to a small family of sequences in the macronucleus, only one of which also hybridizes to pGpC6.295. The latter is a strong candidate for the gene encoding the SerH3 antigen. Sequences homologous to pC6 - but not to pGpC6.295 - are present in strains carrying the other SerH alleles. Shifts in antigen switching during vegetative growth do not result in any detectable DNA rearrangements in the vicinity of the pC6-hybridizing sequence family. Analysis of micronuclear DNA from a homozygous SerH3 strain revealed that it also contains a family of sequences that are homologous to pC6; but, in contrast to the macronuclear DNA, two members of this micronuclear sequence family hybridize to pGpC6.295. Comparison of micro- and macronuclear DNA indicate that some members of the pC6-positive sequence family rearrange during macronuclear development. These rearrangements fall into two classes: those which occur reproducibly, and those which show variability. The gene homologous to pGp6.295 falls into the former category.
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Affiliation(s)
- M M Tondravi
- Department of Biology, Washington University, St. Louis, MO 63130
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