scholarly journals Contrasting Roles of Checkpoint Proteins as Recombination Modulators at Fob1-Ter Complexes with or without Fork Arrest

2009 ◽  
Vol 8 (4) ◽  
pp. 487-495 ◽  
Author(s):  
Bidyut K. Mohanty ◽  
Narendra K. Bairwa ◽  
Deepak Bastia
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna ◽  
Replication Fork ◽  
Intergenic Spacer ◽  
Sensor Kinase ◽  
Adapter Proteins ◽  
Widespread Occurrence ◽  
Checkpoint Proteins ◽  
Nontranscribed Spacer ◽  
Replication Terminus

ABSTRACT The replication terminator protein Fob1 of Saccharomyces cerevisiae specifically interacts with two tandem Ter sites (replication fork barriers) located in the nontranscribed spacer of ribosomal DNA (rDNA) to cause polar fork arrest. The Fob1-Ter complex is multifunctional and controls other DNA transactions such as recombination by multiple mechanisms. Here, we report on the regulatory roles of the checkpoint proteins in the initiation and progression of recombination at Fob1-Ter complexes. The checkpoint adapter proteins Tof1 and Csm3 either positively or negatively controlled recombination depending on whether it was provoked by polar fork arrest or by transcription, respectively. The absolute requirements for these proteins for inducing recombination at an active replication terminus most likely masked their negative modulatory role at a later step of the process. Other checkpoint proteins of the checkpoint adapter/mediator class such as Mrc1 and Rad9, which channel signals from the sensor to the effector kinase, tended to suppress recombination at Fob1-Ter complexes regardless of how it was initiated. We have also discovered that the checkpoint sensor kinase Mec1 and the effector Rad53 were positive modulators of recombination initiated by transcription but had little effect on recombination at Ter. The work also showed that the two pathways were Rad52 dependent but Rad51 independent. Since Ter sites occur in the intergenic spacer of rDNA from yeast to humans, the mechanism is likely to be of widespread occurrence.

scholarly journals Ribosomal DNA Replication Fork Barrier and HOT1Recombination Hot Spot: Shared Sequences but Independent Activities

2000 ◽  
Vol 20 (13) ◽  
pp. 4948-4957 ◽  
Author(s):  
Teresa R. Ward ◽  
Margaret L. Hoang ◽  
Reeta Prusty ◽  
Corine K. Lau ◽  
Ralph L. Keil ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Simple Model ◽  
Ribosomal Rna ◽  
Ribosomal Dna ◽  
Replication Fork ◽  
Hot Spot ◽  
Replication Forks ◽  
Nontranscribed Spacer ◽  
A Site ◽  
Replication Fork Arrest

ABSTRACT In the ribosomal DNA of Saccharomyces cerevisiae, sequences in the nontranscribed spacer 3′ of the 35S ribosomal RNA gene are important to the polar arrest of replication forks at a site called the replication fork barrier (RFB) and also to thecis-acting, mitotic hyperrecombination site calledHOT1. We have found that the RFB and HOT1activity share some but not all of their essential sequences. Many of the mutations that reduce HOT1 recombination also decrease or eliminate fork arrest at one of two closely spaced RFB sites, RFB1 and RFB2. A simple model for the juxtaposition of RFB andHOT1 sequences is that the breakage of strands in replication forks arrested at RFB stimulates recombination. Contrary to this model, we show here that HOT1-stimulated recombination does not require the arrest of forks at the RFB. Therefore, whileHOT1 activity is independent of replication fork arrest,HOT1 and RFB require some common sequences, suggesting the existence of a common trans-acting factor(s).

scholarly journals Mechanism of Regulation of Intrachromatid Recombination and Long-Range Chromosome Interactions in Saccharomyces cerevisiae

2016 ◽  
Vol 36 (10) ◽  
pp. 1451-1463 ◽  
Author(s):  
Shamsu Zaman ◽  
Malay Choudhury ◽  
James C. Jiang ◽  
Pankaj Srivastava ◽  
Bidyut K. Mohanty ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase Ii ◽  
Histone Deacetylase ◽  
Long Range ◽  
Ribosomal Dna ◽  
Replication Fork ◽  
Regulatory Mechanisms ◽  
Content Type ◽  
Nontranscribed Spacer ◽  
Rdna Array

The NAD-dependent histone deacetylase Sir2 controls ribosomal DNA (rDNA) silencing by inhibiting recombination and RNA polymerase II-catalyzed transcription in the rDNA ofSaccharomyces cerevisiae. Sir2 is recruited to nontranscribed spacer 1 (NTS1) of the rDNA array by interaction between the RENT (regulation ofnucleolarsilencing andtelophase exit) complex and the replication terminator protein Fob1. The latter binds to its cognate sites, called replication termini (Ter) or replication fork barriers (RFB), that are located in each copy of NTS1. This work provides new mechanistic insights into the regulation of rDNA silencing and intrachromatid recombination by showing that Sir2 recruitment is stringently regulated by Fob1 phosphorylation at specific sites in its C-terminal domain (C-Fob1), which also regulates long-range Ter-Ter interactions. We show further that long-range Fob1-mediated Ter-Ter interactions intransare downregulated by Sir2. These regulatory mechanisms control intrachromatid recombination and the replicative life span (RLS).

scholarly journals Organization of replication of ribosomal DNA in Saccharomyces cerevisiae.

1988 ◽  
Vol 8 (11) ◽  
pp. 4927-4935 ◽  
Author(s):  
M H Linskens ◽  
J A Huberman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna ◽  
Repeat Unit ◽  
Replication Forks ◽  
Sequence Element ◽  
Autonomously Replicating Sequence ◽  
Nontranscribed Spacer ◽  
Precursor Rna ◽  
Mapping Techniques ◽  
Region Ii

Using recently developed replicon mapping techniques, we have analyzed the replication of the ribosomal DNA in Saccharomyces cerevisiae. The results show that (i) the functional origin of replication colocalizes with an autonomously replicating sequence element previously mapped to the nontranscribed spacer region, (ii) only a fraction of the potential origins are utilized in a single S phase, and (iii) the replication forks moving counter to the direction of transcription of the 37S precursor RNA stop at or near the termination site of transcription. Consequently, most ribosomal DNA is replicated unidirectionally by forks moving in the direction of transcription and most replicons are larger than the repeat unit. The significance of this finding for the replication of abundantly transcribed genes is discussed.

scholarly journals Condensin Loaded onto the Replication Fork Barrier Site in the rRNA Gene Repeats during S Phase in a FOB1-Dependent Fashion To Prevent Contraction of a Long Repetitive Array in Saccharomyces cerevisiae

2006 ◽  
Vol 26 (6) ◽  
pp. 2226-2236 ◽  
Author(s):  
Katsuki Johzuka ◽  
Masahiro Terasawa ◽  
Hideyuki Ogawa ◽  
Tomoko Ogawa ◽  
Takashi Horiuchi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Copy Number ◽  
Replication Fork ◽  
Tandem Repeats ◽  
S Phase ◽  
Rrna Gene ◽  
Nontranscribed Spacer ◽  
Condensin Complex ◽  
Unknown System ◽  
Average Copy

ABSTRACT An average of 200 copies of the rRNA gene (rDNA) is clustered in a long tandem array in Saccharomyces cerevisiae. FOB1 is known to be required for expansion/contraction of the repeats by stimulating recombination, thereby contributing to the maintenance of the average copy number. In Δfob1 cells, the repeats are still maintained without any fluctuation in the copy number, suggesting that another, unknown system acts to prevent repeat contraction. Here, we show that condensin acts together with FOB1 in a functionally complemented fashion to maintain the long tandem repeats. Six condensin mutants possessing severely contracted rDNA repeats were isolated in Δfob1 cells but not in FOB1 + cells. We also found that the condensin complex associated with the nontranscribed spacer region of rDNA with a major peak coincided with the replication fork barrier (RFB) site in a FOB1-dependent fashion. Surprisingly, condensin association with the RFB site was established during S phase and was maintained until anaphase. These results indicate that FOB1 plays a novel role in preventing repeat contraction by regulating condensin association and suggest a link between replication termination and chromosome condensation and segregation.

scholarly journals Checkpoint proteins control morphogenetic events during DNA replication stress in Saccharomyces cerevisiae

2006 ◽  
Vol 175 (5) ◽  
pp. 729-741 ◽  
Author(s):  
Jorrit M. Enserink ◽  
Marcus B. Smolka ◽  
Huilin Zhou ◽  
Richard D. Kolodner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
Cell Morphology ◽  
Replication Fork ◽  
Replication Stress ◽  
Replication Checkpoint ◽  
Checkpoint Proteins ◽  
Checkpoint Kinases ◽  
Dna Replication Checkpoint ◽  
Dna Replication Stress

In response to DNA replication stress in Saccharomyces cerevisiae, the DNA replication checkpoint maintains replication fork stability, prevents precocious chromosome segregation, and causes cells to arrest as large-budded cells. The checkpoint kinases Mec1 and Rad53 act in this checkpoint. Treatment of mec1 or rad53Δ mutants with replication inhibitors results in replication fork collapse and inappropriate partitioning of partially replicated chromosomes, leading to cell death. We describe a previously unappreciated function of various replication stress checkpoint proteins, including Rad53, in the control of cell morphology. Checkpoint mutants have aberrant cell morphology and cell walls, and show defective bud site selection. Rad53 shows genetic interactions with septin ring pathway components, and, along with other checkpoint proteins, controls the timely degradation of Swe1 during replication stress, thereby facilitating proper bud growth. Thus, checkpoint proteins play an important role in coordinating morphogenetic events with DNA replication during replication stress.

Organization of replication of ribosomal DNA in Saccharomyces cerevisiae

1988 ◽  
Vol 8 (11) ◽  
pp. 4927-4935
Author(s):  
M H Linskens ◽  
J A Huberman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna ◽  
Repeat Unit ◽  
Replication Forks ◽  
Sequence Element ◽  
Autonomously Replicating Sequence ◽  
Nontranscribed Spacer ◽  
Precursor Rna ◽  
Mapping Techniques ◽  
Region Ii

Using recently developed replicon mapping techniques, we have analyzed the replication of the ribosomal DNA in Saccharomyces cerevisiae. The results show that (i) the functional origin of replication colocalizes with an autonomously replicating sequence element previously mapped to the nontranscribed spacer region, (ii) only a fraction of the potential origins are utilized in a single S phase, and (iii) the replication forks moving counter to the direction of transcription of the 37S precursor RNA stop at or near the termination site of transcription. Consequently, most ribosomal DNA is replicated unidirectionally by forks moving in the direction of transcription and most replicons are larger than the repeat unit. The significance of this finding for the replication of abundantly transcribed genes is discussed.

scholarly journals Actualización en caracterización molecular de levaduras de interés industrial

2016 ◽  
Vol 18 (2) ◽  
pp. 129 ◽  
Author(s):  
Jorge Alberto Vásquez C ◽  
Mauricio Ramirez Castrillón ◽  
Zulma Isabel Monsalve F
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna

Las levaduras, además de ser un modelo de la investigación biomédica, tienen diversas aplicaciones en la industria alimentaria, en agricultura y la producción de etanol combustible. Dado que la calidad y la cantidad del producto dependen de la dinámica y la frecuencia de los microorganismos presentes en la fermentación, el uso de herramientas de caracterización molecular se ha incrementado y popularizado en las industrias que emplean levaduras. Estas técnicas se basan en la amplificación o análisis por enzimas de restricción de una porción del ADN genómico de levadura y se clasifican de acuerdo a su capacidad de resolución taxonómica para discriminar a nivel inter o intra-específica. La primera parte de la revisión incluye pruebas interespecíficas tales como, análisis de restricción o RFLP para las regiones ITS2, ITS1-5.8, D1 / D2 de los genes 26S ribosomal DNA. La segunda parte incluye, pruebas de uso común para caracterización nivel de cepa, tales como: la amplificación aleatoria del ADN polimórfico (RAPD), análisis cromosómico por electroforesis en gel de campo pulsado (PFGE), análisis de restricción del ADN mitocondrial (ADNmt- RFLP) análisis por mini / micro satélites y la huella genética de ADN por amplificación de regiones interdelta de los transposones Ty. Esta revisión describe y discute los detalles técnicos de los métodos más utilizados para la caracterización molecular de las levaduras y algunos ejemplos de sus aplicaciones en el contexto industrial.Palabras clave: Levaduras, caracterización molecular, identificación intraespecífica especies, Saccharomyces cerevisiae.

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