Institute of Molecular and Cell Biology, University of Tartu, Tartu 51010, Estonia.
J Biol Chem. 2010 Dec 17;285(51):40004-11. doi: 10.1074/jbc.M110.148924. Epub 2010 Oct 20.
DNA replication origins are licensed in early G(1) phase of the cell cycle where the origin recognition complex (ORC) recruits the minichromosome maintenance (MCM) helicase to origins. These pre-replicative complexes (pre-RCs) remain inactive until replication is initiated in the S phase. However, transcriptional activity in the regions of origins can eliminate their functionality by displacing the components of pre-RC from DNA. We analyzed genome-wide data of mRNA and cryptic unstable transcripts in the context of locations of replication origins in yeast genome and found that at least one-third of the origins are transcribed and therefore might be inactivated by transcription. When investigating the fate of transcriptionally inactivated origins, we found that replication origins were repetitively licensed in G(1) to reestablish their functionality after transcription. We propose that reloading of pre-RC components in G(1) might be utilized for the maintenance of sufficient number of competent origins for efficient initiation of DNA replication in S phase.
DNA 复制起点在细胞周期的早期 G1 期被许可,此时起始识别复合物 (ORC) 将微小染色体维持 (MCM) 解旋酶募集到起点。这些前复制复合物 (pre-RC) 在 S 期开始复制之前一直处于非活性状态。然而,起源区域的转录活性可以通过将 pre-RC 的成分从 DNA 上置换下来,从而消除它们的功能。我们分析了酵母基因组中复制起点位置的 mRNA 和隐匿不稳定转录本的全基因组数据,发现至少三分之一的起点被转录,因此可能被转录失活。当研究转录失活起点的命运时,我们发现复制起点在 G1 期被反复许可,以在转录后重新建立其功能。我们提出,G1 期 pre-RC 成分的重新加载可能用于维持足够数量的有能力的起点,以在 S 期有效启动 DNA 复制。