scholarly journals Cis-acting requirements in flanking DNA for the programmed elimination of mse2.9: a common mechanism for deletion of internal eliminated sequences from the developing macronucleus of Tetrahymena thermophila

2001 ◽  
Vol 29 (2) ◽  
pp. 488-498 ◽  
Author(s):  
J. S. Fillingham
Keyword(s):  
Tetrahymena Thermophila ◽  
Common Mechanism ◽  
Cis Acting ◽  
Internal Eliminated Sequences

scholarly journals Functional equivalency and diversity of cis-acting elements among yeast replication origins.

1997 ◽  
Vol 17 (9) ◽  
pp. 5473-5484 ◽  
Author(s):  
S Lin ◽  
D Kowalski
Keyword(s):  
Origin Recognition Complex ◽  
Common Mechanism ◽  
Dna Unwinding ◽  
Replication Origins ◽  
Yeast Saccharomyces Cerevisiae ◽  
Autonomously Replicating Sequence ◽  
Cis Acting ◽  
Dna Elements ◽  
Functional Dna ◽  
Dna Replication Origins

The DNA replication origins of the yeast Saccharomyces cerevisiae require several short functional elements, most of which are not conserved in sequence. To better characterize ARS305, a replicator from a chromosomal origin, we swapped functional DNA elements of ARS305 with defined elements of ARS1. ARS305 contains elements that are functionally exchangeable with ARS1 A and B1 elements, which are known to bind the origin recognition complex; however, the ARS1 A element differs in that it does not require a 3' box adjacent to the essential autonomously replicating sequence consensus. At the position corresponding to ARS1 B3, ARS305 has a novel element, B4, that can functionally substitute for every type of short element (B1, B2, and B3) in the B domain. Unexpectedly, the replacement of element B4 by ARS1 B3, which binds ABF1p and is known as a replication enhancer, inhibited ARS305 function. ARS305 has no short functional element at or near positions corresponding to the B2 elements in ARS1 and ARS307 but contains an easily unwound region whose functional importance was supported by a broad G+C-rich substitution mutation. Surprisingly, the easily unwound region can functionally substitute for the ARS1 B2 element, even though ARS1 B2 was found to possess a distinct DNA sequence requirement. The functionally conserved B2 element in ARS307 contains a known sequence requirement, and helical stability analysis of linker and minilinker mutations suggested that B2 also contains a DNA unwinding element (DUE). Our findings suggest that yeast replication origins employ a B2 element or a DUE to mediate a common function, DNA unwinding during initiation, although not necessarily through a common mechanism.

scholarly journals Multiple effects of mutation on expression of alternative cell surface protein genes in Tetrahymena thermophila.

Genetics ◽  
1992 ◽  
Vol 130 (1) ◽  
pp. 97-104
Author(s):  
D L Smith ◽  
F P Doerder
Keyword(s):  
Gene Expression ◽  
Cell Surface ◽  
Tetrahymena Thermophila ◽  
Culture Media ◽  
Surface Protein ◽  
Cell Surface Protein ◽  
Wild Type ◽  
Negative Effects ◽  
Cis Acting ◽  
Antigen Gene

Abstract Genes at the SerH locus of the ciliated protist Tetrahymena thermophila specify the major (H) surface protein on cells grown at 20-36 degrees. Alternative proteins L, T, S and I are expressed under different conditions of temperature and culture media. Mutants unable to express SerH genes were examined for expression of these proteins, also called immobilization or i-antigens, at both H and non-H conditions. In all instances, one or more i-antigens were expressed in the absence of H, and, in most instances, expression of i-antigens under non-H conditions was also affected. Examples of the latter include both the continued expression of H-replacement antigens and the inability to express certain other i-antigens. Such multiple effects were observed in mutants with trans-acting (rseA, rseB, rseC, RseD) and cis-acting (H1-1 and H1-2) mutations, but not in mutants in which SerH is affected developmentally (B2092, B2101, B2103, B2107). These interactions suggest that the wild-type genes identified by mutation exert both positive and negative effects in the regulation of i-antigen gene expression.

Accurate processing and amplification of cloned germ line copies of ribosomal DNA injected into developing nuclei of Tetrahymena thermophila

1989 ◽  
Vol 9 (3) ◽  
pp. 1092-1099
Author(s):  
M C Yao ◽  
C H Yao
Keyword(s):  
Developmental Stages ◽  
Transformation Efficiency ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Rrna Genes ◽  
Somatic Nucleus ◽  
Dna Breakage ◽  
Cis Acting ◽  
Palindromic Structure ◽  
Rdna Amplification

The ciliate Tetrahymena thermophila contains a chromosomally integrated copy of the rRNA genes (rDNA) in its germinal (micronuclear) genome. These genes are excised from the chromosome through a process involving site-specific DNA breakage, become linear palindromic molecules with added telomeres, and are greatly amplified during development of the somatic nucleus (macronucleus). In this study, we cloned a 15-kilobase segment of the germ line DNA containing these genes and injected it into developing macronuclei of T. thermophila. Up to 11% of injected cells were transformed to the paromomycin-resistant phenotype specified by the injected DNA. Transformation efficiency was dependent on the developmental stages of the injected cells and the integrity of the injected DNA but not the DNA concentration or conformation. The injected DNA was apparently processed and amplified correctly to produce rDNA molecules with the expected linear palindromic structure which carried the appropriate physical markers. Thus, the 15-kilobase DNA contained all cis-acting sequences sufficient for the DNA-processing events leading to rDNA amplification in T. thermophila.

scholarly journals Accurate processing and amplification of cloned germ line copies of ribosomal DNA injected into developing nuclei of Tetrahymena thermophila.

1989 ◽  
Vol 9 (3) ◽  
pp. 1092-1099 ◽  
Author(s):  
M C Yao ◽  
C H Yao
Keyword(s):  
Developmental Stages ◽  
Transformation Efficiency ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Rrna Genes ◽  
Somatic Nucleus ◽  
Dna Breakage ◽  
Cis Acting ◽  
Palindromic Structure ◽  
Rdna Amplification

The ciliate Tetrahymena thermophila contains a chromosomally integrated copy of the rRNA genes (rDNA) in its germinal (micronuclear) genome. These genes are excised from the chromosome through a process involving site-specific DNA breakage, become linear palindromic molecules with added telomeres, and are greatly amplified during development of the somatic nucleus (macronucleus). In this study, we cloned a 15-kilobase segment of the germ line DNA containing these genes and injected it into developing macronuclei of T. thermophila. Up to 11% of injected cells were transformed to the paromomycin-resistant phenotype specified by the injected DNA. Transformation efficiency was dependent on the developmental stages of the injected cells and the integrity of the injected DNA but not the DNA concentration or conformation. The injected DNA was apparently processed and amplified correctly to produce rDNA molecules with the expected linear palindromic structure which carried the appropriate physical markers. Thus, the 15-kilobase DNA contained all cis-acting sequences sufficient for the DNA-processing events leading to rDNA amplification in T. thermophila.

scholarly journals Regulatory sequences for the amplification and replication of the ribosomal DNA minichromosome in Tetrahymena thermophila.

1997 ◽  
Vol 17 (12) ◽  
pp. 7237-7247 ◽  
Author(s):  
P Blomberg ◽  
C Randolph ◽  
C H Yao ◽  
M C Yao
Keyword(s):  
Transcription Initiation ◽  
Tetrahymena Thermophila ◽  
Initiation Site ◽  
Core Region ◽  
Rrna Gene ◽  
Regulatory Sequences ◽  
Coding Region ◽  
Cis Acting ◽  
Rrna Transcription ◽  
Stable Maintenance

We have analyzed the cis-acting sequences that regulate rRNA gene (rDNA) replication in Tetrahymena thermophila. The macronucleus of this ciliated protozoan contains 9,000 copies of a 21-kbp minichromosome in the form of a palindrome comprising two copies of the rDNA. These are derived from a single chromosomally integrated copy during conjugation through selective amplification and are maintained by replicating once per cell cycle during vegetative growth. We have developed a transformation vector and carried out a deletion analysis to determine the minimal sequences required for replication, amplification, and/or stable maintenance of the rDNA molecule. Using constructs containing progressively longer deletions, we show that only a small portion (approximately 900 bp) of the rDNA is needed for extrachromosomal replication and stable maintenance of this molecule. This core region is very near but does not include the rRNA transcription initiation site or its putative promoter, indicating that replication is not dependent on normal rRNA transcription. It includes two nearly identical nuclease-sensitive domains (D1 and D2), one of which (D1) corresponds to the physical origin of replication determined previously. Deletion of both domains abolishes replication, whereas deletion of either domain allows the molecules to replicate, indicating that only one domain is required. In addition to this core region, we have found several DNA segments, including a tandem array of a 21-nucleotide repeat (type II repeats) and sequences within the rRNA coding region, that play distinctive and important roles in maintaining the rDNA at a high copy number.

scholarly journals Tetrahymena thermophila mutants defective in the developmentally programmed maturation and maintenance of the rDNA minichromosome.

Genetics ◽  
1994 ◽  
Vol 137 (2) ◽  
pp. 455-466 ◽  
Author(s):  
G M Kapler ◽  
E Orias ◽  
E H Blackburn
Keyword(s):  
De Novo ◽  
Tetrahymena Thermophila ◽  
Single Copy ◽  
Rrna Gene ◽  
Cis Acting ◽  
New Class ◽  
Controlled Processing ◽  
Sequence Elements ◽  
High Level ◽  
Processing Steps

Abstract The abundant rDNA minichromosome of Tetrahymena thermophila is generated by a series of developmentally controlled processing steps, termed rDNA maturation, during the formation of the new macronucleus in conjugating cells. rDNA maturation involves excision of a region encoding the single copy rRNA gene (rDNA) from its germline location, rearrangement of the rDNA into a palindromic minichromosome, de novo telomere addition, and amplification to approximately 10(4) copies. The rDNA is maintained at this high level in vegetatively growing cells. Using a previously developed genetic scheme for studying rDNA maturation and maintenance, we report the isolation of a new class of mutants defective for rDNA maturation. Several new rDNA maintenance mutants were also obtained. The maturation mutant, rmm10, is severely defective for the production of both monomeric and palindromic rDNA in the developing macronucleus. The mm10 mutation is recessive-lethal and cis-acting. None of the previously identified DNA sequence elements that control rDNA maturation or maintenance is mutated in rmm10. Therefore, additional cis-acting sequence elements must be required for rDNA maturation. Based on our current understanding of rDNA maturation processes, we suggest that the rmm10 mutation affects rDNA excision rather than subsequent rDNA amplification/replication.

scholarly journals Evolutionary Conservation of Sequences Directing Chromosome Breakage and rDNA Palindrome Formation in Tetrahymenine Ciliates

Genetics ◽  
1996 ◽  
Vol 144 (4) ◽  
pp. 1479-1487 ◽  
Author(s):  
Robert S Coyne ◽  
Meng-Chao Yao
Keyword(s):  
Dna Sequence ◽  
Tetrahymena Thermophila ◽  
Chromosome Breakage ◽  
Evolutionary Conservation ◽  
Rdna Locus ◽  
Inverted Repeats ◽  
Ciliated Protozoa ◽  
Evolutionary Time ◽  
Additional Species ◽  
Cis Acting

Extensive, programmed chromosome breakage occurs during formation of the somatic macronucleus of ciliated protozoa. The cis-acting signal directing breakage has been most rigorously defined in Tetrahymena thermophila, where it consists of a 15-bp DNA sequence known as Cbs, for chromosome breakage sequence. We have identified sequences identical or nearly identical to the T. thermophila Cbs at sites of breakage flanking the germline micronuclear rDNA locus of six additional species of Tetrahymena as well as members of two related genera. Other general features of the breakage site are also conserved, but surprisingly, the orientation and number of copies of Cbs are not always conserved, suggesting the occurrence of germline rearrangement events over evolutionary time. At one end of the T. thermophila micronuclear rDNA locus, a pair of short inverted repeats adjacent to Cbs directs the formation of a giant palindromic molecule. We have examined the corresponding sequences from two other Tetrahymena species. We find the sequence to be partially conserved, as previously implied from analysis of macronuclear rDNA, but of variable length and organization.

scholarly journals Elimination of Foreign DNA during Somatic Differentiation in Tetrahymena thermophila Shows Position Effect and Is Dosage Dependent

2005 ◽  
Vol 4 (2) ◽  
pp. 421-431 ◽  
Author(s):  
Yifan Liu ◽  
Xiaoyuan Song ◽  
Martin A. Gorovsky ◽  
Kathleen M. Karrer
Keyword(s):  
Transposable Elements ◽  
Dna Sequences ◽  
Copy Number ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Position Effect ◽  
Dna Elimination ◽  
Internal Eliminated Sequences ◽  
Somatic Genome ◽  
Foreign Dna

ABSTRACT In the ciliate Tetrahymena thermophila, approximately 15% of the germ line micronuclear DNA sequences are eliminated during formation of the somatic macronucleus. The vast majority of the internal eliminated sequences (IESs) are repeated in the micronuclear genome, and several of them resemble transposable elements. Thus, it has been suggested that DNA elimination evolved as a means for removing invading DNAs. In the present study, bacterial neo genes introduced into the germ line micronuclei were eliminated from the somatic genome. The efficiency of elimination from two different loci increased dramatically with the copy number of the neo genes in the micronuclei. The timing of neo elimination is similar to that of endogenous IESs, and they both produce bidirectional transcripts of the eliminated element, suggesting that the deletion of neo occurred by the same mechanism as elimination of endogenous IESs. These results indicate that repetition of an element in the micronucleus enhances the efficiency of its elimination from the newly formed somatic genome of Tetrahymena thermophila. The implications of these data in relation to the function and mechanism of IES elimination are discussed.

Sign in / Sign up

Export Citation Format

Share Document