提出问题：How noncoding transcription influences chromatin states is still unclear. 

研究基础：The Arabidopsis floral repressor gene FLC is quantitatively regulated through an antisense-mediated chromatin silencing mechanism. The FLC antisense transcripts form a cotranscriptional R-loop that is dynamically resolved by RNA 3′ processing factors (FCA and FY), and this is linked to chromatin silencing. 

结果1：Here, we investigate this silencing mechanism and show, using single-molecule DNA fiber analysis, that FCA and FY are required for unimpeded replication fork progression across the Arabidopsis genome. 

结果2：We then employ the chicken DT40 cell line system, developed to investigate sequence-dependent replication and chromatin inheritance, and find that FLC R-loop sequences have an orientation-dependent ability to stall replication forks. 

结论：These data suggest a coordination between RNA 3′ processing of antisense RNA and replication fork progression in the inheritance of chromatin silencing at FLC.

 摘 要 

非编码转录是如何影响染色质状态的还不清楚。拟南芥开花抑制基因FLC通过反义介导的染色质沉默机制被定量调控。FLC反义转录物形成一个共转录R环，主要特征是含有RNA 3′加工因子FCA和FY，其与染色质沉默有关。本文中，作者通过单分子DNA纤维分析深入研究了这种沉默机制，发现FCA和FY是在整个拟南芥基因组中复制进程的不受阻碍非常重要。接着，作者利用DT40细胞系（鸡淋巴瘤细胞）系统，研究了序列依赖性的复制和染色质遗传，发现FLC的R环序列具有阻止复制分叉的能力，并且该能力存在方向依赖性。这些数据表明，反义RNA的RNA 3′加工和复制分叉过程相互协调，共同作用于FLC位点染色质沉默的遗传。