Bidirectional promoters are relatively abundant in eukaryotic genomes, suggesting that they have an important biological significance. As yet, few of these promoters have been characterized in detail. Here, using a promoter::GUS transgene approach has revealed that the intergenic region of Arabidopsis thaliana divergent genes At1g71850 and At1g71860 is an asymmetric bidirectional promoter, which exhibits an orientation-dependent expression profile. The strength of the forward promoter was greater than that of the reverse promoter, and their tissue specificities were not identical. Deletion analyses revealed that this bidirectional promoter could be divided into three functional regions. The basal level and tissue specificity of the promoter in the reverse orientation were regulated positively by region II and negatively by region III, whereas promoter activity in the forward orientation was regulated negatively by region II and positively by region I. Thus the 52-bp stretch of region II had a dual function, enhancing expression in the reverse orientation and suppressing it in the forward orientation. These results demonstrated that the activity of the At1g71850-At1g71860 bidirectional promoter was modulated by complex interactions between both positive and negative cis-acting elements. These findings will enhance our understanding of the regulatory mechanisms of plant bidirectional promoters.

Background: The treatment of non-small cell lung cancer (NSCLC) is challenging due to immune tolerance and evasion. Salidroside (SAL) is an extract in traditional Chinese medicine and has a potential antitumor effect. However, the mechanism of SAL in regulating the immunological microenvironment of NSCLC is yet to be clarified. Methods: The mouse model with Lewis lung cancer cell line (3LL) in C57BL/6 mice was established. And then, the percentage of tumor-infiltrating T cell subsets including Treg was detected in tumor-bearing mice with or without SAL treatment. In vitro, the effect of SAL on the expression of IL-10, Foxp3 and Stub1 and the function of Treg were detected by flow cytometry. Network pharmacology prediction and molecular docking software were used to predict the target of SAL and intermolecular interaction. Furthermore, the effect of SAL on the expression of Hsp70 and the co-localization of Stub1-Foxp3 in Treg was confirmed by flow cytometry and confocal laser microscopy. Finally, Hsp70 inhibitor was used to verify the above molecular expression. Results: We discovered that SAL treatment inhibits the growth of tumor cells by decreasing the percentage of tumor-infiltrated CD4+Foxp3+T cells. SAL treatment downregulates the expression of Foxp3 in Tregs, but increases the expression of Stub1, an E3 ubiquitination ligase upstream of Foxp3, and the expression of Hsp70. Inhibiting the expression of Hsp70 reverses the inhibition of SAL on Foxp3 and disrupts the colocalization of Stub1 and Foxp3 in the nucleus of Tregs. Conclusions: SAL inhibits tumor growth by regulating the Hsp70/stub1/Foxp3 pathway in Treg to suppress the function of Treg. It is a new mechanism of SAL for antitumor therapy.

Background The treatment of non-small cell lung cancer (NSCLC) is challenging due to immune tolerance and evasion. Salidroside (SAL) is an extract in traditional Chinese medicine and has a potential antitumor effect. However, the mechanism of SAL in regulating the immunological microenvironment of NSCLC is yet to be clarified. Methods The mouse model with Lewis lung cancer cell line (3LL) in C57BL/6 mice was established. And then, the percentage of tumor-infiltrating T cell subsets including Treg was detected in tumor-bearing mice with or without SAL treatment. In vitro, the effect of SAL on the expression of IL-10, Foxp3 and Stub1 and the function of Treg were detected by flow cytometry. Network pharmacology prediction and molecular docking software were used to predict the target of SAL and intermolecular interaction. Furthermore, the effect of SAL on the expression of Hsp70 and the co-localization of Stub1-Foxp3 in Treg was confirmed by flow cytometry and confocal laser microscopy. Finally, Hsp70 inhibitor was used to verify the above molecular expression. Results We discovered that SAL treatment inhibits the growth of tumor cells by decreasing the percentage of tumor-infiltrated CD4+Foxp3+T cells. SAL treatment downregulates the expression of Foxp3 in Tregs, but increases the expression of Stub1, an E3 ubiquitination ligase upstream of Foxp3, and the expression of Hsp70. Inhibiting the expression of Hsp70 reverses the inhibition of SAL on Foxp3 and disrupts the colocalization of Stub1 and Foxp3 in the nucleus of Tregs. Conclusions SAL inhibits tumor growth by regulating the Hsp70/stub1/Foxp3 pathway in Treg to suppress the function of Treg. It is a new mechanism of SAL for antitumor therapy.