Goranov Alexi I, Breier Adam M, Merrikh Houra, Grossman Alan D
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Mol Microbiol. 2009 Oct;74(2):454-66. doi: 10.1111/j.1365-2958.2009.06876.x. Epub 2009 Sep 8.
yabA encodes a negative regulator of replication initiation in Bacillus subtilis and homologues are found in many other gram-positive species. YabA interacts with the beta-processivity clamp (DnaN) of DNA polymerase and with the replication initiator and transcription factor DnaA. Because of these interactions, YabA has been proposed to modulate the activity of DnaA. We investigated the role of YabA in regulating replication initiation and the activity of DnaA as a transcription factor. We found that YabA function is mainly limited to replication initiation at oriC. Loss of YabA did not significantly alter expression of genes controlled by DnaA during exponential growth or after replication stress, indicating that YabA is not required for modulating DnaA transcriptional activity. We also found that DnaN activates replication initiation apparently through effects on YabA. Furthermore, association of GFP-YabA with the replisome correlated with the presence of DnaN at replication forks, but was independent of DnaA. Our results are consistent with models in which YabA inhibits replication initiation at oriC, and perhaps DnaA function at oriC, but not with models in which YabA generally modulates the activity of DnaA in response to replication stress.
yabA编码枯草芽孢杆菌复制起始的负调控因子，在许多其他革兰氏阳性菌中也发现了其同源物。YabA与DNA聚合酶的β-持续合成因子（DnaN）以及复制起始蛋白和转录因子DnaA相互作用。由于这些相互作用，有人提出YabA可调节DnaA的活性。我们研究了YabA在调节复制起始和DnaA作为转录因子的活性方面的作用。我们发现YabA的功能主要局限于oriC处的复制起始。在指数生长期或复制应激后，YabA的缺失并未显著改变由DnaA控制的基因的表达，这表明调节DnaA转录活性不需要YabA。我们还发现DnaN显然通过对YabA的作用激活复制起始。此外，GFP-YabA与复制体的结合与复制叉处DnaN的存在相关，但与DnaA无关。我们的结果与YabA抑制oriC处的复制起始以及可能抑制oriC处DnaA功能的模型一致，但与YabA通常响应复制应激调节DnaA活性的模型不一致。
