|
|
|
Research Papers
Department of Microbiology and Immunology, University of California, San Francisco 94143.
Abstract
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. Surprisingly, the rmm11/6 mutation only weakly affects excision of the rDNA from its germ-line location; at least 25% of cells heterozygous for this mutation correctly excise the affected rDNA allele. In heterozygotes, when this rDNA allele is excised, it is also poorly amplified. The rDNA amplification defect caused by this mutation is not overcome by delaying amplification with the DNA synthesis inhibitor aphidicolin, indicating that rDNA excision and amplification are not experimentally separable. Our experiments provide the first evidence that the capacity to amplify the rDNA is restricted in the developing macronucleus. We propose that the rmm11/6 mutation delays excision of the rDNA and that the developmental progression of the macronucleus past a restricted window for amplification is responsible for the severe amplification defect caused by this weak rDNA excision mutation.
This article has been cited by other articles:
![]() |
E. P. Hamilton, S. Williamson, S. Dunn, V. Merriam, C. Lin, L. Vong, J. Russell-Colantonio, and E. Orias The Highly Conserved Family of Tetrahymena thermophila Chromosome Breakage Elements Contains an Invariant 10-Base-Pair Core. Eukaryot. Cell, April 1, 2006; 5(4): 771 - 780. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. L. Morrison, J. S. Yakisich, D. Cassidy-Hanley, and G. M. Kapler TIF1 Represses rDNA Replication Initiation, but Promotes Normal S Phase Progression and Chromosome Transmission in Tetrahymena Mol. Biol. Cell, June 1, 2005; 16(6): 2624 - 2635. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Mohammad, R. D. York, J. Hommel, and G. M. Kapler Characterization of a Novel Origin Recognition Complex-Like Complex: Implications for DNA Recognition, Cell Cycle Control, and Locus-Specific Gene Amplification Mol. Cell. Biol., July 15, 2003; 23(14): 5005 - 5017. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. C. Marsh, E. S. Cole, and D. P. Romero The Transition From Conjugal Development to the First Vegetative Cell Division Is Dependent on RAD51 Expression in the Ciliate Tetrahymena thermophila Genetics, April 1, 2001; 157(4): 1591 - 1598. [Abstract] [Full Text] |
||||
![]() |
Q. Fan and M.-C. Yao A long stringent sequence signal for programmed chromosome breakage in Tetrahymena thermophila Nucleic Acids Res., February 15, 2000; 28(4): 895 - 900. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Mohammad, S. Saha, and G. M. Kapler Three different proteins recognize a multifunctional determinant that controls replication initiation, fork arrest and transcription in Tetrahymena Nucleic Acids Res., February 1, 2000; 28(3): 843 - 851. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. A. Nikiforov, J. F. Smothers, M. A. Gorovsky, and C. D. Allis Excision of micronuclear-specific DNA requires parental expression of Pdd2p andoccursindependentlyfromDNA replication in Tetrahymena thermophila Genes & Dev., November 1, 1999; 13(21): 2852 - 2862. [Abstract] [Full Text] |
||||
![]() |
R. C. Gallagher and E. H. Blackburn A Promoter Region Mutation Affecting Replication of the Tetrahymena Ribosomal DNA Minichromosome Mol. Cell. Biol., May 1, 1998; 18(5): 3021 - 3033. [Abstract] [Full Text] |
||||
![]() |
S. Saha, A. Nicholson, and G. M. Kapler Cloning and Biochemical Analysis of the Tetrahymena Origin Binding Protein TIF1. COMPETITIVE DNA BINDING IN VITRO AND IN VIVO TO CRITICAL rDNA REPLICATION DETERMINANTS J. Biol. Chem., November 21, 2001; 276(48): 45417 - 45426. [Abstract] [Full Text] [PDF] |
||||