春化过程中拟南芥FRIGIDA蛋白介导的FLC位点组蛋白修饰动态转变

FLC是拟南芥开花的核心抑制基因，受多种表观修饰。春化过程，是FLC沉默过程，伴随H3K4me3的下降和H3K27me3的升高。然而，由哪些组蛋白修饰因子和调控因子参与并完成组蛋白修饰剂量的调控，还不清楚。我们研究显示，春化过程抑制H3K4me3甲基转移酶ATX1在FLC位点的招募，但促进H3K27me3甲基转移酶CLF的招募。ATX1和CLF通过与转录因子SUF4互作，招募至FLC位点。春化过程不改变SUF4对ATX1和CLF富集水平，暗示有其它因子参与调控其富集强度。进一步研究发现，支架蛋白FRI同样可以与ATX1和CLF直接互作，且FRI在春化过程中动态减少。我们猜测，春化过程中，FRI通过促进SUF4对ATX1的招募，但抑制对CLF的招募，完成FLC位点H3K4me3向H3K27me3转换，抑制FLC表达并促进开花。拟在此基础上，进一步研究不同修饰因子完成组蛋白修饰转换的分子机制。

Vernalization promotes the transition from vegetative stage to flowering stage in winter-annual accessions Arabidopsis. FLC is the central repressor in flowering time, containing a variety of epigenetic modifications. Vernalization promotes the FLC expression silence, accompanies with reduced H3K4me3 level and induced H3K37me3 level at FLC locus. However, it is unknown that how many histone modification factors are involved in this process and how these histone modifications with opposite functions at FLC locus are switched. Our study showed that the vernalization represses H3K4me3 methyltransferase ATX1 enrichment at FLC locus, while the prolonged cold promotes H3K27me3 methyltransferase CLF enrichment. The biochemistry assays results showed that ATX1 and CLF interact with transcriptional factor SUF4. SUF4 is responsible for ATX1 and CLF recruitment at FLC locus, but this recruitment is independent on vernalization, suggesting that the other cold-induced factors might adjust their changing enrichment. The further study showed that FRIGIDIA (FRI), a scaffold protein, directly binds to ATX1 or CLF. Intriguingly, the protein levels of FRI were downregulated with prolonged cold treatment. These results suggested that FRI might promotes ATX1 recruitment at FLC before vernalization, while the progressively degradation of FRI in turn promotes the SUF4 interaction with CLF and efficient H3K27me3 deposition after vernalization. These dynamic affinities among the SUF4, FRI, ATX1 and CLF might be crucial for H3K4me3 to H3K37me3 transition with prolonged cold. In this study, we are going to investigate how these factors coordinate with each other to modulate the H3K4me3 to H3K37me3 transition with vernalization.