scholarly journals The DNA Polymerase _-Primase Complex: Multiple Functions and Interactions

2003 ◽  
Vol 3 ◽  
pp. 21-33 ◽  
Author(s):  
Marco Muzi-Falconi ◽  
Michele Giannattasio ◽  
Marco Foiani ◽  
Paolo Plevani
Keyword(s):  
Dna Polymerase ◽  
Replication Fork ◽  
De Novo ◽  
Telomere Maintenance ◽  
Cellular Processes ◽  
Eukaryotic Dna ◽  
Initiation Of Dna Replication ◽  
Lagging Strand ◽  
Primase Complex

DNA polymerase _ (pol _) holds a special position among the growing family of eukaryotic DNA polymerases. In fact, pol _ is associated with DNA primase to form a four subunit complex and, as a consequence, is the only enzyme able to start DNA synthesis de novo. Because of this peculiarity the major role of the DNA polymerase _-primase complex (pol-prim) is in the initiation of DNA replication at chromosomal origins and in the discontinuous synthesis of Okazaki fragments on the lagging strand of the replication fork. However, pol-prim seems to play additional roles in other complex cellular processes, such as the response to DNA damage, telomere maintenance, and the epigenetic control of higher order chromatin assembly.

scholarly journals Pol α-primase dependent nuclear localization of the mammalian CST complex

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Joseph M. Kelich ◽  
Harry Papaioannou ◽  
Emmanuel Skordalakes
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Intracellular Localization ◽  
Telomere Maintenance ◽  
Dna Polymerase Alpha ◽  
Localization Signal ◽  
Initiation Of Dna Replication ◽  
Cycle Dependent ◽  
Lagging Strand

AbstractThe human CST complex composed of CTC1, STN1, and TEN1 is critically involved in telomere maintenance and homeostasis. Specifically, CST terminates telomere extension by inhibiting telomerase access to the telomeric overhang and facilitates lagging strand fill in by recruiting DNA Polymerase alpha primase (Pol α-primase) to the telomeric C-strand. Here we reveal that CST has a dynamic intracellular localization that is cell cycle dependent. We report an increase in nuclear CST several hours after the initiation of DNA replication, followed by exit from the nucleus prior to mitosis. We identify amino acids of CTC1 involved in Pol α-primase binding and nuclear localization. We conclude, the CST complex does not contain a nuclear localization signal (NLS) and suggest that its nuclear localization is reliant on Pol α-primase. Hypomorphic mutations affecting CST nuclear import are associated with telomere syndromes and cancer, emphasizing the important role of this process in health.

scholarly journals Preservation of lagging strand integrity at sites of stalled replication by Pol α-primase and 9-1-1 complex

2021 ◽  
Vol 7 (21) ◽  
pp. eabf2278
Author(s):  
Robin van Schendel ◽  
Ron Romeijn ◽  
Helena Buijs ◽  
Marcel Tijsterman
Keyword(s):  
Replication Fork ◽  
Genome Duplication ◽  
De Novo ◽  
Mechanistic Model ◽  
Dna Integrity ◽  
Whole Genome Analysis ◽  
Dna Loss ◽  
Replication Intermediates ◽  
Lagging Strand ◽  
Primase Complex

During genome duplication, the replication fork encounters a plethora of obstacles in the form of damaged bases, DNA–cross-linked proteins, and secondary structures. How cells protect DNA integrity at sites of stalled replication is currently unknown. Here, by engineering “primase deserts” into the Caenorhabditis elegans genome close to replication-impeding G-quadruplexes, we show that de novo DNA synthesis downstream of the blocked fork suppresses DNA loss. We next identify the pol α-primase complex to limit deletion mutagenesis, a conclusion substantiated by whole-genome analysis of animals carrying mutated POLA2/DIV-1. We subsequently identify a new role for the 9-1-1 checkpoint clamp in protecting Okazaki fragments from resection by EXO1. Together, our results provide a mechanistic model for controlling the fate of replication intermediates at sites of stalled replication.

scholarly journals RAD50 and RAD51 Define Two Pathways That Collaborate to Maintain Telomeres in the Absence of Telomerase

Genetics ◽  
1999 ◽  
Vol 152 (1) ◽  
pp. 143-152 ◽  
Author(s):  
Siyuan Le ◽  
J Kent Moore ◽  
James E Haber ◽  
Carol W Greider
Keyword(s):  
Cell Death ◽  
Telomere Length ◽  
Gene Conversion ◽  
De Novo ◽  
Dna Recombination ◽  
Telomere Maintenance ◽  
Triple Mutant ◽  
Yeast Telomerase ◽  
Telomere Lengthening

Abstract Telomere length is maintained by the de novo addition of telomere repeats by telomerase, yet recombination can elongate telomeres in the absence of telomerase. When the yeast telomerase RNA component, TLC1, is deleted, telomeres shorten and most cells die. However, gene conversion mediated by the RAD52 pathway allows telomere lengthening in rare survivor cells. To further investigate the role of recombination in telomere maintenance, we assayed telomere length and the ability to generate survivors in several isogenic DNA recombination mutants, including rad50, rad51, rad52, rad54, rad57, xrs2, and mre11. The rad51, rad52, rad54, and rad57 mutations increased the rate of cell death in the absence of TLC1. In contrast, although the rad50, xrs2, and mre11 strains initially had short telomeres, double mutants with tlc1 did not affect the rate of cell death, and survivors were generated at later times than tlc1 alone. While none of the double mutants of recombination genes and tlc1 (except rad52 tlc1) blocked the ability to generate survivors, a rad50 rad51 tlc1 triple mutant did not allow the generation of survivors. Thus RAD50 and RAD51 define two separate pathways that collaborate to allow cells to survive in the absence of telomerase.

scholarly journals The Function of DNA Polymerase α at Telomeric G Tails Is Important for Telomere Homeostasis

2000 ◽  
Vol 20 (3) ◽  
pp. 786-796 ◽  
Author(s):  
Aegina Adams Martin ◽  
Isabelle Dionne ◽  
Raymund J. Wellinger ◽  
Connie Holm
Keyword(s):  
Telomere Length ◽  
Dna Polymerase ◽  
Telomere Maintenance ◽  
Replication Machinery ◽  
Telomeric Dna ◽  
Dna Polymerase Α ◽  
Telomeric Silencing ◽  
Pass Through ◽  
Telomere Lengthening ◽  
Lagging Strand

ABSTRACT Telomere length control is influenced by several factors, including telomerase, the components of telomeric chromatin structure, and the conventional replication machinery. Although known components of the replication machinery can influence telomere length equilibrium, little is known about why mutations in certain replication proteins cause dramatic telomere lengthening. To investigate the cause of telomere elongation in cdc17/pol1 (DNA polymerase α) mutants, we examined telomeric chromatin, as measured by its ability to repress transcription on telomere-proximal genes, and telomeric DNA end structures in pol1-17 mutants. pol1-17 mutants with elongated telomeres show a dramatic loss of the repression of telomere-proximal genes, or telomeric silencing. In addition,cdc17/pol1 mutants grown under telomere-elongating conditions exhibit significant increases in single-stranded character in telomeric DNA but not at internal sequences. The single strandedness is manifested as a terminal extension of the G-rich strand (G tails) that can occur independently of telomerase, suggesting thatcdc17/pol1 mutants exhibit defects in telomeric lagging-strand synthesis. Interestingly, the loss of telomeric silencing and the increase in the sizes of the G tails at the telomeres temporally coincide and occur before any detectable telomere lengthening is observed. Moreover, the G tails observed incdc17/pol1 mutants incubated at the semipermissive temperature appear only when the cells pass through S phase and are processed by the time cells reach G1. These results suggest that lagging-strand synthesis is coordinated with telomerase-mediated telomere maintenance to ensure proper telomere length control.

scholarly journals Eukaryotic DNA primase appears to act as oligomer in DNA-polymerase-alpha-primase complex

1992 ◽  
Vol 206 (1) ◽  
pp. 7-13 ◽  
Author(s):  
Vladimir N. PODUST ◽  
Olga V. VLADIMIROVA ◽  
Elena N. MANAKOVA ◽  
Olga I. LAVRIK
Keyword(s):  
Dna Polymerase ◽  
Dna Polymerase Alpha ◽  
Dna Primase ◽  
Eukaryotic Dna ◽  
Primase Complex

scholarly journals Overview of RNA G-quadruplex structures

2017 ◽  
Vol 63 (4) ◽  
Author(s):  
Magdalena Małgowska
Keyword(s):  
Three Dimensional ◽  
Telomere Maintenance ◽  
Structural Studies ◽  
Biological Functions ◽  
Cellular Processes ◽  
Novel Drugs ◽  
G Quadruplex ◽  
Conformational Diversity

G-quadruplexes are non-canonical secondary structures which may be formed by guanine rich sequences, both in vitro and in living cells. The number of biological functions assigned to these structural motifs has grown rapidly since the discovery of their involvement in the telomere maintenance. Knowledge of the three-dimensional structures of G-quadruplexes plays an important role in understanding their conformational diversity, physiological functions, and in the design of novel drugs targeting G-quadruplexes. For the last decades, structural studies have been mainly focused on the DNA G-quadruplexes. Their RNA counterparts gained an increased interest along with still-emerging recognition of the central role of RNA in multiple cellular processes. In this review we focus on structural properties of RNA G-quadruplexes, based on high-resolution structures, available in RCSB PDB data base and on structural models. In addition, we point out to the current challenges in this field of research.

scholarly journals The Werner Syndrome Helicase Coordinates Sequential Strand Displacement and FEN1-Mediated Flap Cleavage during Polymerase δ Elongation

2016 ◽  
Vol 37 (3) ◽  
Author(s):  
Baomin Li ◽  
Sita Reddy ◽  
Lucio Comai
Keyword(s):  
Dna Polymerase ◽  
Werner Syndrome ◽  
Physiological Role ◽  
Cooperative Interaction ◽  
Strand Displacement ◽  
Winged Helix ◽  
Werner Syndrome Protein ◽  
Syndrome Protein ◽  
Lagging Strand

ABSTRACT The Werner syndrome protein (WRN) suppresses the loss of telomeres replicated by lagging-strand synthesis by a yet to be defined mechanism. Here, we show that whereas either WRN or the Bloom syndrome helicase (BLM) stimulates DNA polymerase δ progression across telomeric G-rich repeats, only WRN promotes sequential strand displacement synthesis and FEN1 cleavage, a critical step in Okazaki fragment maturation, at these sequences. Helicase activity, as well as the conserved winged-helix (WH) motif and the helicase and RNase D C-terminal (HRDC) domain play important but distinct roles in this process. Remarkably, WRN also influences the formation of FEN1 cleavage products during strand displacement on a nontelomeric substrate, suggesting that WRN recruitment and cooperative interaction with FEN1 during lagging-strand synthesis may serve to regulate sequential strand displacement and flap cleavage at other genomic sites. These findings define a biochemical context for the physiological role of WRN in maintaining genetic stability.

scholarly journals Ku and the Stability of the Genome

2002 ◽  
Vol 2 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Anna A. Friedl
Keyword(s):  
Double Strand Breaks ◽  
Telomere Maintenance ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Cellular Processes ◽  
Molecular Functions ◽  
Ku Proteins ◽  
The Stability ◽  
Dependent Processes

Ku proteins are associated with a variety of cellular processes such as repair of DNA-double-strand breaks, telomere maintenance and retrotransposition. In recent years, we have learned a lot about their cellular and molecular functions and it has turned out that Ku-dependent processes affect the stability of the genome, both positively and negatively, in several ways. This article gives an overview on the role of Ku in determining the shape of the genome.

scholarly journals Telomeric DNA Mediates De Novo PML Body Formation

2009 ◽  
Vol 20 (22) ◽  
pp. 4804-4815 ◽  
Author(s):  
Anneke K. Brouwer ◽  
Joost Schimmel ◽  
Joop C.A.G. Wiegant ◽  
Alfred C.O. Vertegaal ◽  
Hans J. Tanke ◽  
...  
Keyword(s):  
De Novo ◽  
Cell Types ◽  
Promyelocytic Leukemia ◽  
Telomeric Dna ◽  
Body Formation ◽  
Cellular Processes ◽  
Sumo Ligase ◽  
Pml Bodies ◽  
Nuclear Processes

The cell nucleus harbors a variety of different bodies that vary in number, composition, and size. Although these bodies coordinate important nuclear processes, little is known about how they are formed. Among the most intensively studied bodies in recent years is the PML body. These bodies have been implicated in gene regulation and other cellular processes and are disrupted in cells from patients suffering from acute promyelocytic leukemia. Using live cell imaging microscopy and immunofluorescence, we show in several cell types that PML bodies are formed at telomeric DNA during interphase. Recent studies revealed that both SUMO modification sites and SUMO interaction motifs in the promyelocytic leukemia (PML) protein are required for PML body formation. We show that SMC5, a component of the SUMO ligase MMS21-containing SMC5/6 complex, localizes temporarily at telomeric DNA during PML body formation, suggesting a possible role for SUMO in the formation of PML bodies at telomeric DNA. Our data identify a novel role of telomeric DNA during PML body formation.

The role of SMARCAL1 in replication fork stability and telomere maintenance

DNA Repair ◽  
2017 ◽  
Vol 56 ◽  
pp. 129-134 ◽  
Author(s):  
Natalia Lugli ◽  
Sotirios K. Sotiriou ◽  
Thanos D. Halazonetis
Keyword(s):  
Replication Fork ◽  
Telomere Maintenance
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