Abstract
Numerical aberration of the centrosome results in chromosome missegregation, eventually leading to chromosomal instability, a hallmark of human tumor malignancy. Large tumor suppressors 1 and 2 (Lats1 and Lats2) are central kinases in the Hippo pathway and regulate development and tumorigenesis by coordinating the balance between cell proliferation and apoptosis. Importantly, Lats1 and Lats2 also play pivotal roles in cell cycle checkpoint and mitosis. The Lats proteins localize at centrosomes, but their centrosomal functions remain elusive. Here, we generated Lats1-null knockout (Lats1−/−) mice and established Lats1-null mouse embryonic fibroblasts (MEFs). In Lats1−/− MEFs, centrosomes were markedly overduplicated, leading to severe mitotic defects such as chromosome missegregation and cytokinesis failure. We also found that Lats1 physically interacts with Cdc25B phosphatase that localizes both at the centrosome and in the nucleus and regulates the linkage between the centrosome cycle and mitotic progression. Although Lats1 did not phosphorylate Cdc25B, loss of Lats1 in MEFs caused abnormal accumulation of Cdc25B protein and hyperactivation of Cdk2 toward nucleophosmin (NPM/B23), one of the licensing factors involved in centriole duplication. Taken together, these data suggest that Lats1 regulates Cdc25B protein level and subsequent Cdk2 activity, thereby suppressing centrosome overduplication during interphase.
Highlights
Cdk2-cyclin E and Cdk2-cyclin A complexes[8,9]
To elucidate the molecular function of Lats[1] at the centrosome, we generated Large tumor suppressor 1 (Lats1)-null knockout mice by disrupting a part of exon 5 (E5, amino acids 684–853), which encodes the kinase domain (Supplementary Fig. S1A–C online). Both male and female Lats1−/− mice exhibited growth retardation (Supplementary Fig. S1D online) and reduced body weight relative to wild-type mice (Supplementary Fig. S1E and F online), suggesting that depletion of Lats[1] causes dwarfism in mice; this observation is consistent with the phenotypes of two other types of Lats1-knockout mice generated by truncation at the C-terminus[26] (Supplementary Fig. S1A online) or N-terminus[27]
We performed western blot analysis using two kinds of Lats[1] antibodies, CST-C66B5 and Bethyl, which recognize the N-terminal and C-terminal portions of Lats[1], respectively; these analyses confirmed that Lats1−/− mouse embryonic fibroblasts (MEFs) do not express full-length Lats[1] protein or any truncated Lats[1] fragments (Supplementary Fig. S1G online). These results demonstrate that the Lats1−/− MEFs we generated were Lats1-null cells
Summary
Cdk2-cyclin E and Cdk2-cyclin A complexes[8,9]. The Cdc[25] phosphatase family, including Cdc25A, B, and C, is the principal regulator of the activity of the Cdk-cyclin complex during the cell cycle[10]. Cdc25B localizes to the centrosome throughout the cell cycle[11,12,13,14] and regulates centrosome duplication during interphase and microtubule assembly during mitosis[11] Consistent with these functions, overexpression or depletion of Cdc25B causes centriole overduplication or loss of centrosome integrity, respectively, in cultured human cancer cell lines[15,16]. The interaction between Lats[1] and Cdc25B contributed to the destabilization of Cdc25B protein and, subsequently, activated Cdk[2], thereby preventing centrosome overduplication. These findings suggest that Lats[1] stringently regulates the duplication of the centrosome by restricting irrelevant stabilization of Cdc25B, thereby ensuring that the centrosome duplicates once per cell cycle
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 call
