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Repair of DNA double-strand breaks by the non-homologous end-joining pathway is initiated by the binding of Ku to DNA ends. Multiple Ku proteins load onto linear DNAs in vitro. However, in cells, Ku loading is limited to ∼1–2 molecules per DNA end. The mechanisms enforcing this limit are currently unclear. Here, we show that the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs), but not its protein kinase activity, is required to prevent excessive Ku entry into chromatin. Ku accumulation is further restricted by two mechanisms: a neddylation/FBXL12-dependent process that actively removes loaded Ku molecules throughout the cell cycle and a CtIP/ATM-dependent mechanism that operates in S phase. Finally, we demonstrate that the misregulation of Ku loading leads to impaired transcription in the vicinity of DNA ends. Together, our data shed light on the multiple mechanisms operating to prevent Ku from invading chromatin and interfering with other DNA transactions.

Nicotinium Nitrate Monohydrate (NNM) was grown by slow evaporation method. The arrangment of the molecules and hydrogen bonding intractionsin the grown crystal were analyzed using single crystal XRD. The structure, functional groups (vibrational analysis) and electronic properties (Mulliken and HOMO-LUMO analysis) were calculated by the density functional theory (DFT)/B3LYP/wB97XD method using 6–311++G(d,p) basis set. Also, the binding energy and the effect of basis set superposition error (BSSE) on the ring motifs have been investigated. The intermolecular interactions and charge delocalization density of NNM crystal have been analyzed using NBO 3.1 program. The strength of intermolecular interaction was further analyzed by 3D Hirshfeld surface analysis using fingerprint plot. Improved solubility of the title crystal NNM shows an enhanced physio-chemical activity compared to pure vitamin B3 (Nicotinic acid). The antibacterial activity of NNM crystal increased against Staphylococcus aureusa gram-positive bacteria when compared with pure nicotinic acid.

In order to confirm the vibrational assignments, the density functional hypothesis has been used for 6-amino-3-bromo-2-methylpyridine (6A3B2MP). The entire energy distribution is used to materialize the several vibrational modes of 6A3B2MP (TED). The DFT/B3LYP approach is used to examine the molecular optimum limits and electronic characteristics of 6A3B2MP. Investigations have been made into the molecular orbital, Fukui function analysis, natural bond orbital (NBO), and molecular electrostatic potential (MEP) characteristics of 6A3B2MP. Theoretical studies have focused on the UV–vis spectra with different solvents. According to the outcomes of the molecular docking technique, the 6A3B2MP is docked with two target proteins, which is crucial for the emergence of cancer. Therefore, this research paves the door for the development of medicines that are specially formulated.

Stable sols or gels with SrBi2Nb2O9composition were obtained from mixtures of niobium ethoxide, bismuth and strontium 2-ethylhexanoates. SrBi2Nb2O9thin films were prepared by spin-coating a stable precursor solution on Si/SiO2/TiO2/Pt substrates. Randomly oriented 0.3 µm-thick crack-free films were obtained after 10 successive depositions and an heat-treatment of 2 hours at 700°C. Crystallisation occurs at about 550 °C and a pure SrBi2NB2O9phase is obtained at 600°C. P-E hysteresis loops have confirmed the ferroelectric behaviour of the films : they show a remanent polarisation of 2.5 µC/cm2. No fatigue was observed up to 109full switching.

Aiming to identify novel phosphorylation sites in response to DNA double-strand breaks (DSB) inducers, we have isolated a phosphorylation site on KU70. Unexpectedly, a rabbit antiserum raised against this site cross-reacted with a 120 kDa protein in cells treated by DNA DSB inducers. We identified this protein as SAF-A/hnRNP U, an abundant and essential nuclear protein containing regions binding DNA or RNA. The phosphorylation site was mapped at S59 position in a sequence context favoring a "S-hydrophobic" consensus model for DNA-PK phosphorylation site in vivo. This site was exclusively phosphorylated by DNA-PK in response to DNA DSB inducers. In addition, the extent and duration of this phosphorylation was in inverse correlation with the capacity of the cells to repair DSB by nonhomologous end joining. These results bring a new link between the hnRNP family and the DNA damage response. Additionaly, the mapped phospho-site on SAF-A might serve as a potential bio-marker for DNA-PK activity in academic studies and clinical analyses of DNA-PK activators or inhibitors.

Association of the DNA end-binding Ku70/Ku80 heterodimer with the 460-kDa serine/threonine kinase catalytic subunit forms the DNA-dependent protein kinase (DNA-PK) that is required for double-strand break repair by non-homologous recombination in mammalian cells. Recently, we have proposed a model in which the kinase activity is required for translocation of the DNA end-binding subunit Ku along the DNA helix when DNA-PK assembles on DNA ends. Here, we have questioned the consequences of Ku entry into DNA on local DNA processes by using human nuclear cell extracts incubated in the presence of linearized plasmid DNA. As two model processes, we have chosen nucleotide excision repair (NER) of UVC DNA lesions and transcription from viral promoters. We show that although NER efficiency is strongly reduced on linear DNA, it can be fully restored in the presence of DNA-PK inhibitors. Simultaneously, the amount of NER proteins bound to the UVC-damaged linear DNA is increased and the amount of Ku bound to the same DNA molecules is decreased. Similarly, the poor transcription efficiency exhibited by viral promoters on linear DNA is enhanced in the presence of DNA-PK inhibitor concentrations that prevent Ku entry into the DNA substrate molecule. The present results show that DNA-PK catalytic activity can regulate DNA transactions including transcription in the vicinity of double-strand breaks by controlling Ku entry into DNA.

The joint lattice-dynamical model study of the vibrational and elastic properties of paratellurite (α-TeO2) and tellurite (β-TeO2) has been conducted. Emphasis was laid on the crystal chemistry aspects of Raman spectra of these lattices. Results were used to interpret the Raman spectra of two new polymorphs (γ and δ) of tellurium dioxide, and to clarify their relationships with the spectrum of pure TeO2glass.

cis-Dichlorodiammineplatinum(II) (CDDP; cisplatin) is commonly used in combination with ionizing radiation (IR) in the treatment of various malignancies. In vitro, many observations suggest that acquisition of CDDP resistance in cell lines confers cross-resistance to IR, but the molecular mechanisms involved have not been well documented yet. We report here the selection and characterization of a murine CDDP-resistant L1210 cell line (L1210/3R) that exhibits cross-resistance to IR because of an increased capacity to repair double-strand breaks compared with parental cells (L1210/P). In resistant cells, electrophoretic mobility shift assays revealed an increased DNA-end binding activity that could be ascribed, by supershifting the retardation complexes with antibodies, to the autoantigen Ku. The heterodimeric Ku protein, composed of 86-kDa (Ku80) and 70-kDa (Ku70) subunits, is the DNA-targeting component of DNA-dependent protein kinase (DNA-PK), which plays a critical role in mammalian DNA double-strand breaks repair. The increased Ku-binding activity in resistant cells was associated with an overexpression affecting specifically the Ku80 subunit. These data strongly suggest that the increase in Ku activity is responsible for the phenotype of cross-resistance to IR. In addition, these observations, along with previous results from DNA-PK- mutant cells, provide evidence in favor of a role of Ku/DNA-PK in resistance to CDDP. These results suggest that Ku activity may be an important molecular target in cancer therapy at the crossroad between cellular responses to CDDP and IR.

The large nonstoichiometric domain, observed in the La4Ti3O12-rich part of the La4Ti3O12–BaTiO3system, has been shown to correspond to a continuous series of cation-deficient perovskite-related (Ba,La)nTin−δO3n(n≥4δ) microphases. The crystal structures of these microphases have been analyzed by electron diffraction and high-resolution electron microscopy. They can be described as coherent intergrowths of P-perovskite-like blocks La4Ti3O12and Q-perovskite-like blocks BaLa4Ti4O15, respectively, constitutive of the simple basic terms n=4 and n=5 of the previously identified (Ba,La)nTin−1O3nseries. The corresponding BaQLa4(P+Q)Ti3P+4QO12P+15Qmicrophases can thus be denoted by 4P5Qin a compact form. In fact, only the 4P51intergrowth sequences have been observed. Eight of these are clearly shown by direct imaging. No intergrowth terms were observed for compositions ranging from BaLa4Ti4O15(n=5) to Ba2La4Ti5O18(n=6). The ability of the system to develop coherent intergrowths has been discussed in the light of information provided by an accurate analysis of crystal structures of the basic members of the series: La4Ti3O12(n=4), BaLa4Ti4O15(n=5), and Ba2La4Ti5O18(n=6).

The relationships between structure and nonlinear optical response at 1.5 μm in thallium(I) tellurite glasses are investigated. Usually in tellurite glasses, the introduction of a modifier ion changes the basic structural TeO4disphenoid entity progressively into a TeO3trigonal bipyramid via an intermediate TeO3+1polyhedron. This evolution leads to a decrease of the nonlinear refractive index n2. Nevertheless, if a modifier ion such as Tl+also has an ns2lone electron pair, n2increases although the same structural evolution is observed around the tellurium atoms. This result is related to the hyperpolarizability of the thallium oxygen entities, which has been evidenced by the structural study of both thallium(I) tellurite crystals and glasses of the same compositions. With this solid state chemistry approach, the highest non-linear refractive index measured at 1.5 μm (n2=9.10−19m2/W) and reported in oxide glasses has been obtained.

The DNA-dependent protein kinase (DNA-PK) is required for double-strand break repair in mammalian cells. DNA-PK contains the heterodimer Ku and a 460-kDa serine/threonine kinase catalytic subunit (p460). Ku binds in vitro to DNA termini or other discontinuities in the DNA helix and is able to enter the DNA molecule by an ATP-independent process. It is clear from in vitro experiments that Ku stimulates the recruitment to DNA of p460 and activates the kinase activity toward DNA-binding protein substrates in the vicinity. Here, we have examined in human nuclear cell extracts the influence of the kinase catalytic activity on Ku binding to DNA. We demonstrate that, although Ku can enter DNA from free ends in the absence of p460 subunit, the kinase activity is required for Ku translocation along the DNA helix when the whole Ku/p460 assembles on DNA termini. When the kinase activity is impaired, DNA-PK including Ku and p460 is blocked at DNA ends and prevents their processing by either DNA polymerization, degradation, or ligation. The control of Ku entry into DNA by DNA-PK catalytic activity potentially represents an important regulation of DNA transactions at DNA termini.

The TeO2-rich part of the TeO2-Nb2O5 system has been investigated by temperature programmed X-ray diffraction and differential scanning calorimetry. Three invariant equilibria have been observed: one eutectic reaction (8 mol% NbO2.5, TE=690±5 °C, LE TeO2+Nb2Te4O13), one peritectic reaction (incongruent melting, at 766±5 °C, of the Nb2Te4O13 compound) and one congruent melting reaction (congruent melting, at 810±5 °C, of the Nb2Te3O11 compound). A large glass-forming domain has been evidenced (0 to 25 mol% NbO2.5). The thermal behaviour of these glasses has been followed. The glass transition, crystallization temperatures and the nature of crystalline phases formed have been determined.

The crystal structure of Bi2W2O9 has been solved by single crystal X-ray diffraction data analysis and refined to R=0.046 for 991 independent reflections. Bi2W2O9 crystallizes with orthorhombic symmetry, Pna21 space group, Z=4, a=5.440(1), b=5.413(1), c=23.740(5) Å. The model previously proposed by Watanabe et al., i.e. Bi2O2 layers interleaved with ReO3-like slabs of W2O7, has been confirmed. The distortion of the W2O7 octahedral network has been analysed and compared to that observed in homologous Aurivillius phases.

The crystal structure of the rhombohedral (R3̄m) Bi0.75Sr0.25O1.375phase has been determined at room and high temperature using single crystal neutron diffraction. It can be described at all temperatures as the regular repetition of three fluorite-like sheets shifted with respect to one another by a vector μ = 2 (a/3 + b/3 + c/3) and thus separated by an intersheet space free of anions. Interstitial anions partially occupy delocalized sites in the vicinity of the unsubstituted interface Bi-layers and are responsible for the high ionic conductivity of this phase. They are mainly located on the fluorite-like sheet side of this Bi-layer at room temperature. At high temperature, they partly migrate to the opposite side, i.e., the intersheet side, a phenomenon which results in the β2⇒ β1transition and a sudden increase of the conductivity. In light of these and previous results the different behavior of various alkaline earth-doped rhombehedral phases (Ca, Sr, Ba) and of the La-doped homologue is analyzed and rationalized.