The dynamics of genome replication using deep sequencing

Peer reviewedPublisher PD

Origin-dependent initiation of DNA replication within telomeric sequences

Replication of telomeres requires the action of telomerase, the semi-conservative replication machinery and the stabilization of the replication fork during passage through telomeric DNA. Whether vertebrate telomeres support initiation of replication has not been experimentally addressed. Using Xenopus cell free extracts we established a system to study replication initiation within linear telomeric DNA substrates. We show binding of TRF2 to telomeric DNA, indicating that exogenous DNA exclusively composed of telomeric repeats is recognized by shelterin components. Interaction with telomere binding proteins is not sufficient to prevent a DNA damage response. Notably, we observe regulated assembly of the pre-replicative complex proteins ORC2, MCM6 and Cdc6 to telomeric DNA. Most importantly, we detect origin-dependent replication of telomeric substrates under conditions that inhibit checkpoint activation. These results indicate that pre-replicative complexes assemble within telomeric DNA and can be converted into functional origins

Role of replication protein A as sensor in activation of the S-phase checkpoint in Xenopus egg extracts

Uncoupling between DNA polymerases and helicase activities at replication forks, induced by diverse DNA lesions or replication inhibitors, generate long stretches of primed single-stranded DNA that is implicated in activation of the S-phase checkpoint. It is currently unclear whether nucleation of the essential replication factor RPA onto this substrate stimulates the ATR-dependent checkpoint response independently of its role in DNA synthesis. Using Xenopus egg extracts to investigate the role of RPA recruitment at uncoupled forks in checkpoint activation we have surprisingly found that in conditions in which DNA synthesis occurs, RPA accumulation at forks stalled by either replication stress or UV irradiation is dispensable for Chk1 phosphorylation. In contrast, when both replication fork uncoupling and RPA hyperloading are suppressed, Chk1 phosphorylation is inhibited. Moreover, we show that extracts containing reduced levels of RPA accumulate ssDNA and induce spontaneous, caffeine-sensitive, Chk1 phosphorylation in S-phase. These results strongly suggest that disturbance of enzymatic activities of replication forks, rather than RPA hyperloading at stalled forks, is a critical determinant of ATR activation

Direct non transcriptional role of NF-Y in DNA replication

NF-Y is a heterotrimeric transcription factor, which plays a pioneer role in the transcriptional control of promoters containing the CCAAT-box, among which genes involved in cell cycle regulation, apoptosis and DNA damage response. The knock-down of the sequence-specific subunit NF-YA triggers defects in S-phase progression, which lead to apoptotic cell death. Here, we report that NF-Y has a critical function in DNA replication progression, independent from its transcriptional activity. NF-YA colocalizes with early DNA replication factories, its depletion affects the loading of replisome proteins to DNA, among which Cdc45, and delays the passage from early to middle-late S phase. Molecular combing experiments are consistent with a role for NF-Y in the control of fork progression. Finally, we unambiguously demonstrate a direct non-transcriptional role of NF-Y in the overall efficiency of DNA replication, specifically in the DNA elongation process, using a Xenopus cell-free system. Our findings broaden the activity of NF-Y on a DNA metabolism other than transcription, supporting the existence of specific TFs required for proper and efficient DNA replication

Histone H4K20 methylation mediated chromatin compaction threshold ensures genome integrity by limiting DNA replication licensing

Cell cycle and replication need to be tightly regulated to ensure genome stability in mammalian cells. Here the authors provide a link between chromatin structure and DNA replication regulation by showing that chromatin compaction limits replication licensing thereby promoting genome integrity

Methods in DNA replication

International audienc

Pathologie des étrangers ou des migrants. Problèmes cliniques et thérapeutiques, enjeux de santé publique

Pathology of the strangers or the migrants. Clinical and therapeutical problems, stakes of public health. Denis MECHALI Numerous health problems are noticed in immigrant people or foreigners. Many are similar of those of natives but some are specific to this population. Specific and technical knowledge is essential, especially for diseases unknown in natives. But, even in these cases, physician has to know other aspects, particularly epidemiologic and social aspects. Severity and duration of the pathology must be evaluated for the patient and the circle (especially for transmissible disease). In the same manner, feasibility and cost of diagnosis and therapy must be known and assessed. An accurate thinking must permit to be in harmony with the three matters: technical relevance, satisfactory answer for patients and acceptable value in term of public health.Pathologie des étrangers ou des migrants. Problèmes cliniques et thérapeutiques, enjeux de santé publique. Denis MECHALI Les problèmes de santé posés par les sujets migrants ou étrangers sont multiples. Ils ne sont pas toujours spécifiques. Beaucoup sont semblables à ceux de l'ensemble de la collectivité. Une connaissance technique spécifique est indispensable pour certaines affections absentes chez les autochtones. Mais, même dans ces cas, le médecin doit faire appel à d'autres éléments, épidémiologiques et sociaux notamment, pour avoir une vision exacte. Il faut en effet évaluer la probabilité d'une pathologie donnée, sa gravité à court moyen ou long terme pour l'individu et son entourage, en particulier s'il s'agit d'une pathologie transmissible. Cela aboutit à évaluer les possibilités et les coûts diagnostiques et thérapeutiques. Une réflexion précise doit permettre d'harmoniser les trois registres d'une pertinence technique, d'une réponse satisfaisante pour les intéressés et d'une valeur acceptable en terme de Santé publique.Patología de los extranjeros o de los migrantes. Problemas clínicos y terapeúticos, puesta de salud pública. Denis MECHALI Los problemas de salud planteados por los individuos migrantes o extranjeros son multiples. No son siempre específicos. Muchos se parecen a los del conjunto de la colectividad. Cierto conocimiento técnico específico es imprecindible para cíertas afeccíones ausentes para los autóctonos. Pero incluso en esos casos el médico debe interesarse en otros elementos, epidemiólogicos y sociales particulamente, para tener una visión exacta. Hay que evaluar efectivamente la probabilidad de una patología dada, su gravedad a corto, medio o largo plazo para el individuo y su entorno, en particular si se trata de una patología transmisible. Esto tiene como consecuencia la evaluación de las posibilidades y los costos diagnósticos y terapeúticos. Una reflexión precisa debe permitir la amortiguación de los tres registros de una pertinencia técnica, una respuesta satisfactoria para los interesados y un valor aceptable en término de Salud pública.Mechali Denis. Pathologie des étrangers ou des migrants. Problèmes cliniques et thérapeutiques, enjeux de santé publique. In: Revue européenne des migrations internationales, vol. 6, n°3,1990. pp. 99-127

Finite-Time Attitude Control of Uncertain Quadrotor Aircraft via Continuous Terminal Sliding-Mode-Based Active Anti-Disturbance Approach

This research addresses the problem of robust attitude control for a quadrotor operating in an environment polluted with lumped disturbances. A new continuous terminal sliding mode-based active anti-disturbance control (CTSMBAADC) is proposed by innovatively introducing a finite-time disturbance observer (FTDO) in homogeneous continuous nonsingular terminal sliding mode control (HCNTSMC) law. The HCNTSMC scheme drives the states of the system to the reference setpoint in finite-time. Rigorous stability analysis of the feedback loop system is based on input-to-state stability (ISS) concept and more importantly Lyapunov theory. Real-time experiments are performed to validate the designed control law. Results witness that the proposed control structure offers superior performance in terms of robustness and accuracy while avoiding the singularity problem and significantly alleviating the chattering phenomenon

Spécification d'une origine de réplication par des facteurs de transcription chez xenopus laevis

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF