Gene Amplification

Publication Title: 
Cell

The amplification of ribosomal DNA during development of the somatic macronucleus in Tetrahymena thermophila was analyzed by genetic and molecular biological techniques. We have identified an alternate form of the rDNA, structurally distinguishable from the wild-type by an extra cutting site for Bam HI in its nontranscribed spacer. The altered rDNA was inherited in crosses in a simple Mendelian fashion, consistent with the presence of only one rRNA gene copy per haploid genome in the micronucleus.

Author(s): 
Pan, W. C.
Orias, E.
Flacks, M.
Blackburn, E. H.
Publication Title: 
Cell

A novel form of extrachromosomal rDNA has been identified in conjugating Tetrahymena cells. This rDNA consists of 11 kb linear double-stranded DNA molecules, each containing a single rRNA gene copy. The DNA sequence, tandemly repeated CCCCAA (Blackburn and Gall, 1978) found at the termini of extrachromosomal palindromic rDNA (the macronuclear form found in vegetatively growing cells), is also present at the corresponding terminus of the 11 kb rDNA.

Author(s): 
Pan, W. C.
Blackburn, E. H.
Publication Title: 
Cell

A novel form of extrachromosomal rDNA has been identified in conjugating Tetrahymena cells. This rDNA consists of 11 kb linear double-stranded DNA molecules, each containing a single rRNA gene copy. The DNA sequence, tandemly repeated CCCCAA (Blackburn and Gall, 1978) found at the termini of extrachromosomal palindromic rDNA (the macronuclear form found in vegetatively growing cells), is also present at the corresponding terminus of the 11 kb rDNA.

Author(s): 
Pan, W. C.
Blackburn, E. H.
Publication Title: 
Genes & Development

During development of the somatic macronucleus of Tetrahymena thermophila, the rDNA is excised from its germ-line chromosome, rearranged into a palindrome, and amplified to 10(4) copies. We have identified a cis-acting germ-line mutation, rmm11/6, that prevents amplification of the rDNA in all but approximately 1 in 10(5) cells when it is the only rDNA allele in the developing macronucleus. The rmm11/6 mutation resides in a conserved element required for excision, the chromosome breakage sequence (Cbs) flanking the 3' end of the rDNA.

Author(s): 
Kapler, G. M.
Blackburn, E. H.
Publication Title: 
Molecular and Cellular Biology

The macronuclear rRNA genes (rDNA) in the ciliate Tetrahymena thermophila are normally palindromic linear replicons, containing two copies of the replication origin region in inverted orientation. A circular plasmid containing a single Tetrahymena rRNA gene (one half palindrome) joined to a tandem repeat of a 1.9-kilobase (kb) rDNA segment encompassing the rDNA replication origin and known replication control elements was used to transform Tetrahymena macronuclei by microinjection.

Author(s): 
Yu, G. L.
Blackburn, E. H.
Publication Title: 
Cold Spring Harbor Symposia on Quantitative Biology
Author(s): 
Yao, M. C.
Blackburn, E.
Gall, J. G.
Publication Title: 
Proceedings of the National Academy of Sciences of the United States of America

A mutation that confers resistance to the drug paromomycin is shown to be in the structural gene that codes for the ribosomal RNA in Tetrahymena. This observation was made by exploiting a variant of the ribosomal DNA that distorts amplification of this locus when a new somatic nucleus develops during conjugation. Because the allelic forms of this locus have a restriction endonuclease site polymorphism, it was possible to correlate drug resistance with presence of a specific allele. The genetic results have been confirmed by sequence analysis (presented elsewhere).

Author(s): 
Bruns, P. J.
Katzen, A. L.
Martin, L.
Blackburn, E. H.
Publication Title: 
Cell

A novel genetic scheme was used to isolate mutants altered in the formation or maintenance of amplified rDNA in the Tetrahymena macronucleus. One such mutant had a cis-acting rDNA mutation that affected the ability of mutant rDNA molecules to replicate in macronuclei in the presence of a wild-type (B strain) rDNA. The mutant rDNA was lost from these heterozygous macronuclei during vegetative cell divisions, although it was maintained normally in the homozygous or hemizygous state.

Author(s): 
Larson, D. D.
Blackburn, E. H.
Yaeger, P. C.
Orias, E.
Publication Title: 
Tropical medicine & international health: TM & IH

OBJECTIVES: Many countries are now adopting artemisinin-based combination therapy (ACT) for treatment of Plasmodium falciparum malaria. In multi-drug resistant areas in South East Asia amplifications of the pfmdr1 gene are frequent and tentatively associated with reduced susceptibility to the common quinoline partner drugs mefloquine and lumefantrine. In Africa where amodiaquine is one of the favoured quinoline partner drugs in ACT, studies on multi-drug resistance associated pfmdr1 gene amplifications are urgent.

Author(s): 
Holmgren, Gabrielle
Björkman, Anders
Gil, José Pedro
Publication Title: 
Tropical medicine & international health: TM & IH

OBJECTIVE: Artemether-lumefantrine (AL), presently the most favoured combination therapy against uncomplicated Plasmodium falciparum malaria in Africa, has recently shown to select for the pfmdr1 86N allele. The objective of this study was to search for the selection of other mutations potentially involved in artemether-lumefantrine tolerance and/or resistance, i.e. pfmdr1 gene amplification, pfmdr1 Y184F, S1034C, N1042D, D1246Y, pfcrt S163R and PfATP6 S769N.

Author(s): 
Sisowath, Christin
Ferreira, Pedro E.
Bustamante, Leyla Y.
Dahlstrom, Sabina
Mårtensson, Andreas
Björkman, Anders
Krishna, Sanjeev
Gil, José P.

Pages

Subscribe to RSS - Gene Amplification