RNA binding proteins HLP1 and HLP2 coordinately regulate alternative polyadenylation in Arabidopsis
【摘要】：Alternative polyadenylation(APA) is a widespread mechanism for gene regulation and has been implicated in development and the pathophysiology of diseases. Pre-m RNA can generate transcript isoforms with different coding sequence or alternative 3′-UTR via APA,to enlarge the diversity and complexity of transcriptome. The molecular mechanisms of APA is intricated and remains to be elucidated in plants. Our previous work identified HLP1 as a novel 3′-end processing factors and HLP1 mutation caused thousands of poly(A) sites shifts. Here we report HLP2,the ortholog of HLP1,can also regulates APA. Phenotype analysis shows HLP2 regulate flowering time in a FLC-dependent way,and hlp1hlp2 double mutant are embryo lethal,implying the significance of HLP1 and HLP2 in plant development. Both HLP1 and HLP2 are located in nucleus and have the same expression pattern. The mutation of HLP2 leads to similar APA shift with that of hlp1 mutant,particularly,a distal-to-proximal poly(A) site shift in FCA,a direct target of HLP1 and HLP2,leads to upregulation of FLC and delayed flowering. Biochemistry assay prove HLP1 and HLP2 can form a heterodimer,suggesting that HLP1 and HLP2 regulate APA in a synergetic manner. Interestingly,HLP1 negatively modulates HLP2 expression by regulating HLP2 transcript APA. Taken together,our results demonstrate that HLP1 and HLP2 bind directly to certain RNA targets to control the selection of poly(A) sites in a synergetic mode to regulate flowering time. The results in this study shed new light on the role of RBPs-directed RNA processing in plant development.