Abstract
Tumour radiotherapy resistance involves the cell cycle pathway. CDC25 phosphatases are key cell cycle regulators. However, how CDC25 activity is precisely controlled remains largely unknown. Here, we show that LIM domain-containing proteins, such as FHL1, increase inhibitory CDC25 phosphorylation by forming a complex with CHK2 and CDC25, and sequester CDC25 in the cytoplasm by forming another complex with 14-3-3 and CDC25, resulting in increased radioresistance in cancer cells. FHL1 expression, induced by ionizing irradiation in a SP1- and MLL1-dependent manner, positively correlates with radioresistance in cancer patients. We identify a cell-penetrating 11 amino-acid motif within LIM domains (eLIM) that is sufficient for binding CHK2 and CDC25, reducing the CHK2–CDC25 and CDC25–14-3-3 interaction and enhancing CDC25 activity and cancer radiosensitivity accompanied by mitotic catastrophe and apoptosis. Our results provide novel insight into molecular mechanisms underlying CDC25 activity regulation. LIM protein inhibition or use of eLIM may be new strategies for improving tumour radiosensitivity.
Highlights
Tumour radiotherapy resistance involves the cell cycle pathway
Protein fractionation experiments performed by fast protein liquid chromatography (FPLC) revealed that, in the presence or absence of ionizing radiation (IR), the elution pattern of four-and-a-half LIM domain protein 1 (FHL1) overlapped with that of the CDC25C and CHK2 proteins or that of the CDC25C and 14-3-3e proteins (Fig. 1g)
The reason why there are no marked protein mobility differences between IR and non-IR samples may be that the protein complexes are so large (4440 kDa) that posttranslational modifications of the components of the complexes, such as CDC25C and CHK2, may not be sufficient for alteration of the size of the protein complexes due to limited resolution of the FPLC used
Summary
Tumour radiotherapy resistance involves the cell cycle pathway. CDC25 phosphatases are key cell cycle regulators. We show that LIM domain-containing proteins, such as FHL1, increase inhibitory CDC25 phosphorylation by forming a complex with CHK2 and CDC25, and sequester CDC25 in the cytoplasm by forming another complex with 14-3-3 and CDC25, resulting in increased radioresistance in cancer cells. We identify a cell-penetrating 11 amino-acid motif within LIM domains (eLIM) that is sufficient for binding CHK2 and CDC25, reducing the CHK2–CDC25 and CDC25–14-3-3 interaction and enhancing CDC25 activity and cancer radiosensitivity accompanied by mitotic catastrophe and apoptosis. When phosphorylated at serine 216 (S216) by the checkpoint kinases CHK1 and CHK2 in response to DNA damage, human CDC25C binds to members of the 14-3-3 family of proteins, sequestering CDC25C in the cytoplasm and thereby inhibiting CDC25C phosphatase activity[8,9]. We found that IR-inducible LIM proteins, such as FHL1, inhibit CDC25C activity, resulting in radioresistance in cancer cells. ELIM peptides are cell-permeable and increases radiation sensitivity in cancer cells by increasing CDC25 activity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
