The fungal CCAAT-binding complex and HapX display highly variable but evolutionary conserved synergetic promoter-specific DNA recognition
The fungal CCAAT-binding complex and HapX display highly variable but evolutionary conserved synergetic promoter-specific DNA recognition
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DOI：
10.1093/nar/gkaa109
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发表时间：
2020-04-17
影响因子：
14.9
通讯作者：
Hortschansky, Peter
中科院分区：
文献类型：
--
作者：
Furukawa, Takanori;Scheven, Mareike Thea;Hortschansky, Peter
为了维持铁的动态平衡，微生物已经进化出摄取、储存和解毒必需金属铁的微调机制。在人类病原体烟曲霉中，真菌特异性的bZIP型转录因子HapX协调对铁饥饿和铁过剩的适应，因此对毒力至关重要。以往的研究表明，HapX同源二聚体与CCAAT结合复合体(CBC)相互作用，协同结合两部分DNA基序，但HapX-DNA识别模式尚未解决。在此，结合体内(遗传学和ChIPseq)、体外(表面等离子共振)和系统发育分析，证实了CBC：HapX：DNA相互作用具有惊人的可塑性。CBC：HapX蛋白复合体识别的DNA基序包括一个两部分DNA结合位点5‘-CSAATN(12)RWT-3’和一个额外的5‘-TKAN-3’基序，位于CCAAT基序下游11-23个核苷酸，即偶尔与两部分结合位点的3‘端重叠。利用20个已分解的曲霉物种基因组进行的系统发育比较表明，CBC：HapX复合体对DNA的识别显示出启动子特异性的跨物种保守，而不是调节子特异性的保守。此外，我们还证明了CBC：HapX相互作用对于HapX的所有已知功能都是绝对必要的。CBC：HapX：DNA相互作用的可塑性允许微调CBC：HapX结合的特异性，从而支持病原体对其宿主生态位的适应。
To sustain iron homeostasis, microorganisms have evolved fine-tuned mechanisms for uptake, storage and detoxification of the essential metal iron. In the human pathogen Aspergillus fumigatus, the fungal-specific bZIP-type transcription factor HapX coordinates adaption to both iron starvation and iron excess and is thereby crucial for virulence. Previous studies indicated that a HapX homodimer interacts with the CCAAT-binding complex (CBC) to cooperatively bind bipartite DNA motifs; however, the mode of HapX-DNA recognition had not been resolved. Here, combination of in vivo (genetics and ChIPseq), in vitro (surface plasmon resonance) and phylogenetic analyses identified an astonishing plasticity of CBC:HapX:DNA interaction. DNA motifs recognized by the CBC:HapX protein complex comprise a bipartite DNA binding site 5'-CSAATN(12)RWT-3' and an additional 5'-TKAN-3' motif positioned 11-23 bp downstream of the CCAAT motif, i.e. occasionally overlapping the 3'-end of the bipartite binding site. Phylogenetic comparison taking advantage of 20 resolved Aspergillus species genomes revealed that DNA recognition by the CBC:HapX complex shows promoter-specific cross-species conservation rather than regulon-specific conservation. Moreover, we show that CBC:HapX interaction is absolutely required for all known functions of HapX. The plasticity of the CBC:HapX:DNA interaction permits fine tuning of CBC:HapX binding specificities that could support adaptation of pathogens to their host niches.