| Estimation of the Minimum Number of Replication Origins Per Chromosome in any Organism
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Author:
Date:
2020-10-20
[Abstract] Eukaryote nuclear genomes predominantly replicate through multiple replication origins. The number of replication origins activated per chromosome during the S-phase duration may vary according to many factors, but the predominant one is replication stress. Several studies have applied different approaches to estimate the number and map the positions of the replication origins in various organisms. However, without a parameter to restrict the minimum of necessary origins, less sensitive techniques may suggest conflicting results. The estimation of the minimum number of replication origins (MO) per chromosome is an innovative method that allows the establishment of a threshold, which serves as a parameter for genomic approaches that map origins. For this, the MO can be easily ...
[摘要] [摘要] 比率可能因多种因素而变化，但最主要的因素是复制应力。一些研究应用了不同的方法来估计复制源在不同生物体中的数量和位置。然而，如果没有一个参数来限制必要起源的最小值，那么不太敏感的技术可能会产生相互矛盾的结果。估计每个染色体的最小复制源数量（MO）是一种创新的方法，它允许建立一个阈值，作为绘制起源的基因组方法的参数。为此，MO可以很容易地通过一个公式得到，这个公式需要作为参数：染色体大小、S期持续时间和复制率。在基因组数据库（如NCBI）中可以获得任何生物体的染色体大小，通过监测DNA复制来估计S期的持续时间，并通过DNA组合方法获得复制率。 提供了一种简单、快速的估算MO的方法一个新的方法学框架来协助研究任何有机体。
关键词： DNA复制，复制来源，复制率，S期持续时间，染色体大小
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| SMART (Single Molecule Analysis of Resection Tracks) Technique for Assessing DNA end-Resection in Response to DNA Damage
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Author:
Date:
2020-08-05
[Abstract] DNA double strand breaks (DSBs) are among the most toxic lesions affecting genome integrity. DSBs are mainly repaired through non-homologous end joining (NHEJ) and homologous recombination (HR). A crucial step of the HR process is the generation, through DNA end-resection, of a long 3′ single-strand DNA stretch, necessary to prime DNA synthesis using a homologous region as a template, following DNA strand invasion. DNA end resection inhibits NHEJ and triggers homology-directed DSB repair, ultimately guaranteeing a faithful DNA repair. Established methods to evaluate the DNA end-resection process are the immunofluorescence analysis of the phospho-S4/8 RPA32 protein foci, a marker of DNA end-resection, or of the phospho-S4/8 RPA32 protein levels by Western blot. Recently, the Single ...
[摘要] [摘要] DNA双链断裂（dsb）是影响基因组完整性的最具毒性的损伤之一。dsb主要通过非同源末端连接（NHEJ）和同源重组（HR）进行修复。HR过程的一个关键步骤是通过DNA末端切除，产生一个长的3′单链DNA链，这是在DNA链入侵后，以同源区域为模板进行DNA合成所必需的。DNA末端切除抑制NHEJ并触发同源定向的DSB修复，最终保证DNA的可靠修复。已建立的评价DNA末端切除过程的方法是免疫荧光法分析磷酸化S4/8rpa32蛋白病灶（DNA末端切除的标志物）或磷酸化S4/8rpa32蛋白水平。近年来，切除轨迹单分子分析（SMART）被认为是一种可靠的方法，可以通过免疫荧光法观察S期特异性DNA损伤剂（如喜树碱）处理细胞后产生的长3′单链DNA尾。然后，通过图像分析软件（如Photoshop）测量DNA束长度，评价DNA末端切除机的处理能力。DNA纤维的制备是在非变性条件下进行的，因此免疫荧光只检测DSB处理产生的特定的3′单链DNA尾。
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| DNA Fiber Assay upon Treatment with Ultraviolet Radiations
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Author:
Date:
2017-06-05
[Abstract] Genome stability is continuously challenged by a wide range of DNA damaging factors. To promote a correct DNA repair and cell survival, cells orchestrate a coordinated and finely tuned cascade of events collectively known as the DNA Damage Response (DDR). Ultra Violet (UV) rays are among the main environmental sources of DNA damage and a well recognized cancer risk factor. UV rays induce the formation of toxic cyclobutane-type pyrimidine dimers (CPD) and [6-4]pyrimidine-pyrimidone (6-4PP) photoproducts which trigger the activation of the intra-S phase cell cycle checkpoint (Kaufmann, 2010) aimed at preventing replication fork collapse, late origin firing, and stabilizing fragile sites (Branzei and Foiani, 2009). To monitor the activation of the intra-S phase checkpoint in response to UV ...
[摘要] 基因组稳定性不断受到DNA损伤因素的广泛影响。为了促进正确的DNA修复和细胞存活，细胞协调统一称为DNA损伤反应（DDR）的协调和精细调整的事件级联。超紫外线（UV）是DNA损伤的主要环境来源之一，也是公认的癌症危险因素。紫外线诱导形成毒性环丁烷型嘧啶二聚体（CPD）和[6-4]嘧啶嘧啶酮（6-4PP）光产物，其触发S期细胞周期检查点的活化（Kaufmann，2010），目的在于防止复制叉崩溃，晚期起火和稳定脆弱场所（Branzei和Foiani，2009）。为了监测响应于UV型C（UVC）暴露的S-S相检查点的激活，DNA纤维测定可用于分析新的起始点和DNA合成速率（Jackson等， ，1998; Merrick等人，2004; Alfano等人，2016）。 DNA纤维测定技术在90年代被设想，然后通过使用并入新生DNA链中的胸苷类似物（如CldU和IdU）进一步开发。通过用这些类似物以连续模式处理细胞，可以通过携带不同荧光团的特异性抗体来观察细胞，可以监测复制叉活性并评估其如何受到紫外辐射或其他试剂的影响。
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