scholarly journals Genetic and molecular analysis of the SOE1 gene: a tRNA(3Glu) missense suppressor of yeast cdc8 mutations.

Genetics ◽  
1990 ◽  
Vol 124 (3) ◽  
pp. 523-531 ◽  
Author(s):  
J Y Su ◽  
L Belmont ◽  
R A Sclafani
Keyword(s):  
Mitochondrial Dna ◽  
Dna Replication ◽  
Kinase Activity ◽  
Gene Dosage ◽  
Temperature Sensitive ◽  
Permissive Temperature ◽  
Chromosome X ◽  
Mitochondrial Functions ◽  
Mitochondrial Dna Replication

Abstract The CDC8 gene of Saccharomyces cerevisiae encodes deoxythymidylate (dTMP) kinase and is required for nuclear and mitochondrial DNA replication in both the mitotic and meiotic cell cycles. All cdc8 temperature-sensitive mutants are partially defective in meiotic and mitochondrial functions at the permissive temperature. In a study of revertants of temperature-sensitive cdc8 mutants, the SOE201 and SOE1 mutants were isolated. The SOE201 mutant is a disome of chromosome X to which the cdc8 gene maps. Using the chromosome X aneuploids to vary cdc8 gene dosage, we demonstrate that different levels of dTMP kinase activity are required for mitotic, meiotic or mitochondrial DNA replication. The SOE1 mutant contains a dominant suppressor that suppresses five different cdc8 alleles but does not suppress a complete cdc8 deletion. The SOE1 gene is located less than 1.5 cM from the CYH2 gene on chromosome VII and is adjacent to the TSM437-CYH2 region, with the gene order being SOE1-TSM437-CYH2. SOE1 is an inefficient suppressor that can neither suppress the cdc8 hypomorphic phenotype nor restore dTMP kinase activity in vitro. SOE1 is a single C to T mutation in the anticodon of a tRNA(3Glu) gene and thereby, produces a missense suppressor tRNA capable of recognizing AAA lysine codons. We propose that the resultant lysine to glutamate change stabilizes thermo-labile dTMP kinase molecules in the cell.

scholarly journals In Vitro-Reconstituted Nucleoids Can Block Mitochondrial DNA Replication and Transcription

Cell Reports ◽  
2014 ◽  
Vol 8 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Géraldine Farge ◽  
Majda Mehmedovic ◽  
Marian Baclayon ◽  
Siet M.J.L. van den Wildenberg ◽  
Wouter H. Roos ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Dna Replication ◽  
Mitochondrial Dna Replication

scholarly journals Twinkle is not the mitochondrial DNA replicative helicase in C. elegans, but may have alternate mitochondrial functions

2019 ◽  
Author(s):  
Hope R. Henderson ◽  
Liliya Euro ◽  
Anu Suomalainen ◽  
Andrew Dillin
Keyword(s):  
Mitochondrial Dna ◽  
Caenorhabditis Elegans ◽  
Dna Replication ◽  
Mitochondrial Fission ◽  
Mitochondrial Diseases ◽  
Inner Mitochondrial Membrane ◽  
Replicative Helicase ◽  
Mitochondrial Functions ◽  
Alternative Function ◽  
Mitochondrial Dna Replication

ABSTRACTDysfunction of mitochondrial DNA replication machinery is a common cause of mitochondrial diseases. The minimal mammalian replisome is made up of DNA polymerase gamma, replicative helicase Twinkle, and single-stranded DNA binding protein. The replisome is localized to the inner mitochondrial membrane and serves as the site of mitochondrial DNA replication and mitochondrial fission. Recently, a sequence homolog of Twinkle was uncovered in the nematode Caenorhabditis elegans. Here, we characterized this homolog, twnk-1, and report that twnk-1 does not function as the primary mitochondrial DNA replicative helicase in this species, as loss of twnk-1 does not result in reduce mitochondrial DNA levels, or result in other expected mitochondrial dysfunctions such as reduced oxygen consumption rates, increased sensitivity to metabolic perturbations, or reduced muscle function. Instead, twnk-1 mutants have increased mitochondrial DNA as they age, and exhibit phenotypes associated with mitochondrial stress, including reduced fecundity, an activation of the mitochondrial unfolded protein response, and mitochondrial fragmentation. Our results suggest in Caenorhabditis elegans, twnk-1 does not function as the mitochondrial DNA replicative helicase, but has an alternative function in regulating mitochondrial function.

scholarly journals A function for the mitochondrial chaperonin Hsp60 in the structure and transmission of mitochondrial DNA nucleoids in Saccharomyces cerevisiae

2003 ◽  
Vol 163 (3) ◽  
pp. 457-461 ◽  
Author(s):  
Brett A. Kaufman ◽  
Jill E. Kolesar ◽  
Philip S. Perlman ◽  
Ronald A. Butow
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitochondrial Dna ◽  
High Resolution ◽  
Temperature Sensitive ◽  
Permissive Temperature ◽  
Wild Type ◽  
Template Strand ◽  
Daughter Cells ◽  
Ts Mutant

The yeast mitochondrial chaperonin Hsp60 has previously been implicated in mitochondrial DNA (mtDNA) transactions: it is found in mtDNA nucleoids associated with single-stranded DNA; it binds preferentially to the template strand of active mtDNA ori sequences in vitro; and wild-type (ρ+) mtDNA is unstable in hsp60 temperature-sensitive (ts) mutants grown at the permissive temperature. Here we show that the mtDNA instability is caused by a defect in mtDNA transmission to daughter cells. Using high resolution, fluorescence deconvolution microscopy, we observe a striking alteration in the morphology of mtDNA nucleoids in ρ+ cells of an hsp60-ts mutant that suggests a defect in nucleoid division. We show that ρ− petite mtDNA consisting of active ori repeats is uniquely unstable in the hsp60-ts mutant. This instability of ori ρ− mtDNA requires transcription from the canonical promoter within the ori element. Our data suggest that the nucleoid dynamics underlying mtDNA transmission are regulated by the interaction between Hsp60 and mtDNA ori sequences.

Selective inhibition of mutant human mitochondrial DNA replication in vitro by peptide nucleic acids

1997 ◽  
Vol 15 (2) ◽  
pp. 212-215 ◽  
Author(s):  
Robert W. Taylor ◽  
Patrick F. Chinnery ◽  
Douglass M. Turnbull ◽  
Robert N. Lightowlers
Keyword(s):  
Mitochondrial Dna ◽  
Dna Replication ◽  
Nucleic Acids ◽  
Peptide Nucleic Acids ◽  
Selective Inhibition ◽  
Human Mitochondrial Dna ◽  
Mitochondrial Dna Replication

scholarly journals GSP1 and GSP2, genetic suppressors of the prp20-1 mutant in Saccharomyces cerevisiae: GTP-binding proteins involved in the maintenance of nuclear organization.

1993 ◽  
Vol 13 (4) ◽  
pp. 2152-2161 ◽  
Author(s):  
P Belhumeur ◽  
A Lee ◽  
R Tam ◽  
T DiPaolo ◽  
N Fortin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
Essential Gene ◽  
Negative Control ◽  
Temperature Sensitive ◽  
Vitro Assay ◽  
Gtp Binding ◽  
Genetic Suppressors ◽  
Multicopy Suppressors

The temperature-sensitive mutation prp20-1 of Saccharomyces cerevisiae exhibits a pleiotropic phenotype associated with a general failure to maintain a proper organization of the nucleus. Its mammalian homolog, RCC1, is not only reported to be involved in the negative control of chromosome condensation but is also believed to assist in the coupling of DNA replication to the entry into mitosis. Recent studies on Xenopus RCC1 have strongly suggested a further role for this protein in the formation or maintenance of the DNA replication machinery. To elucidate the nature of the various components required for this PRP20 control pathway in S. cerevisiae, we undertook a search for multicopy suppressors of a prp20 thermosensitive mutant. Two genes, GSP1 and GSP2, were identified that encode almost identical polypeptides of 219 and 220 amino acids. Sequence analyses of these proteins show them to contain the ras consensus domains involved in GTP binding and metabolism. The levels of the GSP1 transcript are about 10-fold those of GSP2. As for S. cerevisiae RAS2, GSP2 expression exhibits carbon source dependency, while GSP1 expression does not. GSP1 is an essential gene, and GSP2 is not required for cell viability. We show that GSP1p is nuclear, that it can bind GTP in an in vitro assay, and finally, that a mutation in GSP1p which activates small ras-like proteins by increasing the stability of the GTP-bound form causes a dominant lethal phenotype. We believe that these two gene products may serve in regulating the activities of the multicomponent PRP20 complex.

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