| 1. |
- Kochenova, Olga V, et al.
(författare)
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Yeast DNA polymerase ζ maintains consistent activity and mutagenicity across a wide range of physiological dNTP concentrations
- 2017
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 45:3, s. 1200-1218
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Tidskriftsartikel (refereegranskat)abstract
- In yeast, dNTP pools expand drastically during DNA damage response. We show that similar dNTP elevation occurs in strains, in which intrinsic replisome defects promote the participation of error-prone DNA polymerase ζ (Polζ) in replication of undamaged DNA. To understand the significance of dNTP pools increase for Polζ function, we studied the activity and fidelity of four-subunit Polζ (Polζ4) and Polζ4-Rev1 (Polζ5) complexes in vitro at 'normal S-phase' and 'damage-response' dNTP concentrations. The presence of Rev1 inhibited the activity of Polζ and greatly increased the rate of all three 'X-dCTP' mispairs, which Polζ4 alone made extremely inefficiently. Both Polζ4 and Polζ5 were most promiscuous at G nucleotides and frequently generated multiple closely spaced sequence changes. Surprisingly, the shift from 'S-phase' to 'damage-response' dNTP levels only minimally affected the activity, fidelity and error specificity of Polζ complexes. Moreover, Polζ-dependent mutagenesis triggered by replisome defects or UV irradiation in vivo was not decreased when dNTP synthesis was suppressed by hydroxyurea, indicating that Polζ function does not require high dNTP levels. The results support a model wherein dNTP elevation is needed to facilitate non-mutagenic tolerance pathways, while Polζ synthesis represents a unique mechanism of rescuing stalled replication when dNTP supply is low.
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| 2. |
- Boldinova, Elizaveta O., et al.
(författare)
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DNA Damage Tolerance by Eukaryotic DNA Polymerase and Primase PrimPol
- 2017
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 18:7
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Forskningsöversikt (refereegranskat)abstract
- PrimPol is a human deoxyribonucleic acid (DNA) polymerase that also possesses primase activity and is involved in DNA damage tolerance, the prevention of genome instability and mitochondrial DNA maintenance. In this review, we focus on recent advances in biochemical and crystallographic studies of PrimPol, as well as in identification of new protein-protein interaction partners. Furthermore, we discuss the possible functions of PrimPol in both the nucleus and the mitochondria.
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| 3. |
- Boldinova, Elizaveta O., et al.
(författare)
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Optimization of the expression, purification and polymerase activity reaction conditions of recombinant human PrimPol
- 2017
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- Human PrimPol is a DNA primase/polymerase involved in DNA damage tolerance and prevents nuclear genome instability. PrimPol is also localized to the mitochondria, but its precise function in mitochondrial DNA maintenance has remained elusive. PrimPol works both as a translesion (TLS) polymerase and as the primase that restarts DNA replication after a lesion. However, the observed biochemical activities of PrimPol vary considerably between studies as a result of different reaction conditions used. To reveal the effects of reaction composition on PrimPol DNA polymerase activity, we tested the polymerase activity in the presence of various buffer agents, salt concentrations, pH values and metal cofactors. Additionally, the enzyme stability was analyzed under various conditions. We demonstrate that the reaction buffer with pH 6-6.5, low salt concentrations and 3 mM Mg2+ or 0.3-3 mM Mn2+ cofactor ions supports the highest DNA polymerase activity of human PrimPol in vitro. The DNA polymerase activity of PrimPol was found to be stable after multiple freeze-thaw cycles and prolonged protein incubation on ice. However, rapid heat-inactivation of the enzyme was observed at 37 degrees C. We also for the first time describe the purification of human PrimPol from a human cell line and compare the benefits of this approach to the expression in Escherichia coli and in Saccharomyces cerevisiae cells. Our results show that active PrimPol can be purified from E. coli and human suspension cell line in high quantities and that the activity of the purified enzyme is similar in both expression systems. Conversely, the yield of full-length protein expressed in S. cerevisiae was considerably lower and this system is therefore not recommended for expression of full-length recombinant human PrimPol.
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| 4. |
- Sawicka, Marta, et al.
(författare)
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The dimeric architecture of checkpoint kinases Mec1(ATR) and Tel1(ATM) reveal a common structural organization
- 2016
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Ingår i: Journal of Biological Chemistry. - : Elsevier. - 0021-9258 .- 1083-351X. ; 291:26, s. 13436-13447
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Tidskriftsartikel (refereegranskat)abstract
- The phosphatidylinositol 3-kinase-related protein kinases are key regulators controlling a wide range of cellular events. The yeast Tel1 and Mec1Ddc2 complex (ATM and ATR-ATRIP in humans) play pivotal roles in DNA replication, DNA damage signaling, and repair. Here, we present the first structural insight for dimers of Mec1Ddc2 and Tel1 using single-particle electron microscopy. Both kinases reveal a head to head dimer with one major dimeric interface through the N-terminal HEAT (named after Huntingtin, elongation factor 3, protein phosphatase 2A, and yeast kinase TOR1) repeat. Their dimeric interface is significantly distinct from the interface of mTOR complex 1 dimer, which oligomerizes through two spatially separate interfaces. We also observe different structural organizations of kinase domains of Mec1 and Tel1. The kinase domains in the Mec1Ddc2 dimer are located in close proximity to each other. However, in the Tel1 dimer they are fully separated, providing potential access of substrates to this kinase, even in its dimeric form.
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| 5. |
- Stojkovic, Gorazd, et al.
(författare)
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Oxidative DNA damage stalls the human mitochondrial replisome
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress is capable of causing damage to various cellular constituents, including DNA. There is however limited knowledge on how oxidative stress influences mitochondrial DNA and its replication. Here, we have used purified mtDNA replication proteins, i.e. DNA polymerase. holoenzyme, the mitochondrial single-stranded DNA binding protein mtSSB, the replicative helicase Twinkle and the proposed mitochondrial translesion synthesis polymerase PrimPol to study lesion bypass synthesis on oxidative damage-containing DNA templates. Our studies were carried out at dNTP levels representative of those prevailing either in cycling or in non-dividing cells. At dNTP concentrations that mimic those in cycling cells, the replication machinery showed substantial stalling at sites of damage, and these problems were further exacerbated at the lower dNTP concentrations present in resting cells. PrimPol, the translesion synthesis polymerase identified inside mammalian mitochondria, did not promote mtDNA replication fork bypass of the damage. This argues against a conventional role for PrimPol as a mitochondrial translesion synthesis DNA polymerase for oxidative DNA damage; however, we show that Twinkle, the mtDNA replicative helicase, is able to stimulate PrimPol DNA synthesis in vitro, suggestive of an as yet unidentified role of PrimPol in mtDNA metabolism.
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