The gene for the α-subunit of ATPase: a site of homologous recombination in plant mitochondrial DNA also functions in somatic hybrid cells

1992 ◽  
Vol 84 (1-2) ◽  
pp. 33-38 ◽  
Author(s):  
H. Honda ◽  
A. Hirai
Keyword(s):  
Mitochondrial Dna ◽  
Homologous Recombination ◽  
Somatic Hybrid ◽  
Hybrid Cells ◽  
Α Subunit ◽  
Plant Mitochondrial Dna ◽  
A Site

Mitochondrial DNA Amplification in Somatic Hybrid Cells of Grasses

1988 ◽  
pp. 267-268
Author(s):  
P. Ozias-Akins ◽  
Z. Tabaeizadeh ◽  
D. R. Pring ◽  
I. K. Vasil
Keyword(s):  
Mitochondrial Dna ◽  
Somatic Hybrid ◽  
Dna Amplification ◽  
Hybrid Cells

A mitochondrial retroplasmid integrates into mitochondrial DNA by a novel mechanism involving the synthesis of a hybrid cDNA and homologous recombination

1994 ◽  
Vol 14 (10) ◽  
pp. 6419-6432
Author(s):  
C C Chiang ◽  
J C Kennell ◽  
L A Wanner ◽  
A M Lambowitz
Keyword(s):  
Mitochondrial Dna ◽  
Homologous Recombination ◽  
Rrna Gene ◽  
Template Switching ◽  
Transcript Analysis ◽  
Wild Type ◽  
Mitochondrial Trna ◽  
Integration Mechanism ◽  
Circular Dnas ◽  
Simple Integration

The Mauriceville and Varkud mitochondrial plasmids of Neurospora spp. are closely related, small circular DNAs that propagate via an RNA intermediate and reverse transcription. Although the plasmids ordinarily replicate autonomously, they can also integrate into mitochondrial DNA (mtDNA), yielding defective mtDNAs that in some cases cause senescence. To investigate the integration mechanism, we analyzed four cases in which the Varkud plasmid integrated into the mitochondrial small rRNA gene, three in wild-type subcultures and one in a senescent mutant. Our analysis suggests that the integrations occurred by the plasmid reverse transcriptase template switching between the plasmid transcript and internal sequences in the mitochondrial small rRNA to yield hybrid cDNAs that circularized and recombined homologously with the mtDNA. The integrated plasmid sequences are transcribed, presumably from the mitochondrial small rRNA promoters, resulting in hybrid RNAs containing the 5' segment of the mitochondrial small rRNA linked head-to-tail to the full-length plasmid transcript. Analysis of additional senescent mutants revealed three cases in which the plasmid used the same mechanism to integrate at other locations in the mtDNA. In these cases, circular variant plasmids that had incorporated a mitochondrial tRNA or tRNA-like sequence by template switching integrated by homologous recombination at the site of the corresponding tRNA or tRNA-like sequence in mtDNA. This simple integration mechanism involving template switching to generate a hybrid cDNA that integrates homologously could have been used by primitive retroelements prior to the acquisition of a specialized integration machinery.

scholarly journals The Mitochondrial DNA (mtDNA)-Associated Protein SWIB5 Influences mtDNA Architecture and Homologous Recombination

2017 ◽  
pp. tpc.00899.2016 ◽  
Author(s):  
Jonas Blomme ◽  
Olivier Van Aken ◽  
Jelle Van Leene ◽  
Teddy Jégu ◽  
Riet Maria De Rycke ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Homologous Recombination

scholarly journals Fbh1 Limits Rad51-Dependent Recombination at Blocked Replication Forks

2009 ◽  
Vol 29 (17) ◽  
pp. 4742-4756 ◽  
Author(s):  
Alexander Lorenz ◽  
Fekret Osman ◽  
Victoria Folkyte ◽  
Sevil Sofueva ◽  
Matthew C. Whitby
Keyword(s):  
Homologous Recombination ◽  
Gene Conversion ◽  
Replication Fork ◽  
Direct Repeat ◽  
Dna Helicase ◽  
Replication Forks ◽  
Site Specific ◽  
Replicative Stress ◽  
Recombinant Formation ◽  
A Site

ABSTRACT Controlling the loading of Rad51 onto DNA is important for governing when and how homologous recombination is used. Here we use a combination of genetic assays and indirect immunofluorescence to show that the F-box DNA helicase (Fbh1) functions in direct opposition to the Rad52 orthologue Rad22 to curb Rad51 loading onto DNA in fission yeast. Surprisingly, this activity is unnecessary for limiting spontaneous direct-repeat recombination. Instead it appears to play an important role in preventing recombination when replication forks are blocked and/or broken. When overexpressed, Fbh1 specifically reduces replication fork block-induced recombination, as well as the number of Rad51 nuclear foci that are induced by replicative stress. These abilities are dependent on its DNA helicase/translocase activity, suggesting that Fbh1 exerts its control on recombination by acting as a Rad51 disruptase. In accord with this, overexpression of Fbh1 also suppresses the high levels of recombinant formation and Rad51 accumulation at a site-specific replication fork barrier in a strain lacking the Rad51 disruptase Srs2. Similarly overexpression of Srs2 suppresses replication fork block-induced gene conversion events in an fbh1Δ mutant, although an inability to suppress deletion events suggests that Fbh1 has a distinct functionality, which is not readily substituted by Srs2.

scholarly journals Identification of Amino Acid Residues in the α, β, and γ Subunits of the Epithelial Sodium Channel (ENaC) Involved in Amiloride Block and Ion Permeation

1997 ◽  
Vol 109 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Laurent Schild ◽  
Estelle Schneeberger ◽  
Ivan Gautschi ◽  
Dmitri Firsov
Keyword(s):  
Amino Acid ◽  
Ion Selectivity ◽  
Site Directed Mutagenesis ◽  
Ion Permeation ◽  
Amino Acid Residues ◽  
Α Subunit ◽  
Na Ions ◽  
Membrane Spanning ◽  
A Site ◽  
Epithelial Sodium Channel Enac

The amiloride-sensitive epithelial Nachannel (ENaC) is a heteromultimeric channel made of three αβγ subunits. The structures involved in the ion permeation pathway have only been partially identified, and the respective contributions of each subunit in the formation of the conduction pore has not yet been established. Using a site-directed mutagenesis approach, we have identified in a short segment preceding the second membrane-spanning domain (the pre-M2 segment) amino acid residues involved in ion permeation and critical for channel block by amiloride. Cys substitutions of Gly residues in β and γ subunits at position βG525 and γG537 increased the apparent inhibitory constant (Ki) for amiloride by >1,000-fold and decreased channel unitary current without affecting ion selectivity. The corresponding mutation S583 to C in the α subunit increased amiloride Ki by 20-fold, without changing channel conducting properties. Coexpression of these mutated αβγ subunits resulted in a nonconducting channel expressed at the cell surface. Finally, these Cys substitutions increased channel affinity for block by externalZn2+ ions, in particular the αS583C mutant showing a Ki for Zn2+of 29 μM. Mutations of residues αW582L or βG522D also increased amiloride Ki, the later mutation generating a Ca2+blocking site located 15% within the membrane electric field. These experiments provide strong evidence that αβγ ENaCs are pore-forming subunits involved in ion permeation through the channel. The pre-M2 segment of αβγ subunits may form a pore loop structure at the extracellular face of the channel, where amiloride binds within the channel lumen. We propose that amiloride interacts with Na+ions at an external Na+binding site preventing ion permeation through the channel pore.

Preparation Of Factor IX-Deficient Human Plasma Using RFF-IX/1 Monoclonal Antibody

1981 ◽  
Author(s):  
F Rotblat ◽  
A H Goodall ◽  
G Janossy ◽  
G Kemble ◽  
D P O’Brien ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Cell Line ◽  
Factor Ix ◽  
Hybrid Cells ◽  
Spleen Cells ◽  
High Affinity ◽  
A Cell ◽  
A Site ◽  
Monoclonal Cell Line ◽  
Mouse Myeloma

A cell line that secretes a monoclonal antibody to factor IX has been produced by fusing spleen cells from a mouse that had been hyper immunised to purified factor IX with mouse myeloma cells (line P3-NSI/I-Ag4-1). Hybrid cells were selected and a monoclonal cell line has been established in culture. This cell line secretes an IgGl(k) antibody (RFF-IX/1) with high affinity for a site related to the coagulant function of factor IX.Monoclonal antibody was partially purified from ascitic fluid from mice implanted with the RFF-IX/1 secreting cells by precipitation at 50% saturation with ammonium sulphate. This fraction has typically 630 NIH units/ml anti IX activity and 13.5 mg/ml protein. It was coupled to cyanogen bromide activated Sepharose 2B in the ratio of 9 mg. protein/1 ml gel. A column containing 10 ml of this gel removed all the assayable factor IX from the first 280 ml of normal ci.trated plasma that was passed over it. After that volume small amounts of factor IX could be detected in the effluent. Subsequently 10-20% of the factor IX activity adsorbed could be recovered by eluting the column with 3 M potassium iodide.Immuno-affinity depleted plasma could be used as substrate in a one-stage factor IX assay under routine laboratory conditions and was undistinguishable for that purpose from severe Christmas disease plasma.

scholarly journals Homologous recombination in plant cells is enhanced byin vivoinduction of double strand breaks into DNA by a site-specific endonuclease

1993 ◽  
Vol 21 (22) ◽  
pp. 5034-5040 ◽  
Author(s):  
Holger Puchta ◽  
Bernard Dujon ◽  
Barbara Hohn
Keyword(s):  
Homologous Recombination ◽  
Plant Cells ◽  
Double Strand Breaks ◽  
Site Specific ◽  
Strand Breaks ◽  
A Site

Surface H-2 antigen concentration requirement of somatic hybrid cells for IgM-mediated cytotoxicity

Nature ◽  
1974 ◽  
Vol 249 (5456) ◽  
pp. 461-463 ◽  
Author(s):  
NAZARIO RUBIO
Keyword(s):  
Somatic Hybrid ◽  
Hybrid Cells ◽  
Antigen Concentration

Cytological identification of colony formation of intergeneric somatic hybrid cells

PROTOPLASMA ◽  
1978 ◽  
Vol 96 (1-2) ◽  
pp. 23-38 ◽  
Author(s):  
G. Gosch ◽  
J. Reinert
Keyword(s):  
Somatic Hybrid ◽  
Colony Formation ◽  
Hybrid Cells ◽  
Intergeneric Somatic Hybrid
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