Abstract：
How CRISPR-Cas systems defend bacteria and archaea against invading genetic elements is well understood, but less is known about their regulation. In the cyanobacterium Synechocystis sp. PCC 6803, the expression of one of the three different CRISPR-Cas systems responds to changes in environmental conditions. The cas operon promoter of this system is controlled by the light- and redox-responsive transcription factor RpaB binding to an HLR1 motif, resulting in transcriptional activation at low light intensities. However, the strong promoter that drives transcription of the cognate repeat-spacer array is not controlled by RpaB. Instead, the leader transcript is bound by the redox-sensitive RNA helicase CrhR. Crosslinking coupled with mass spectrometry analysis and site-directed mutagenesis revealed six residues involved in the CrhR-RNA interaction, with C371 being critically important. Thus, the expression of a type III-Dv CRISPR-Cas system is linked to the redox status of the photosynthetic cell at the transcriptional and post-transcriptional levels.
摘要：
CRISPR-Cas系统如何保护细菌和古细菌免受入侵的遗传因素的侵害是众所周知的，但对他们的监管知之甚少。在蓝细菌集胞藻中。PCC6803，三种不同的CRISPR-Cas系统之一的表达响应环境条件的变化。该系统的cas操纵子启动子受与HLR1基序结合的光-和氧化还原反应性转录因子RpaB控制，导致在低光照强度下的转录激活。然而,驱动同源重复间隔区阵列转录的强启动子不受RpaB控制。相反，前导转录物被氧化还原敏感性RNA解旋酶CrhR结合。交联结合质谱分析和定点诱变揭示了参与CrhR-RNA相互作用的六个残基，C371至关重要。因此，III-DvCRISPR-Cas系统的表达与光合细胞在转录和转录后水平的氧化还原状态有关。
