USP44 regulates centrosome positioning to prevent aneuploidy and suppress tumorigenesis
Ying Zhang, … , Jan van Deursen, Paul J. Galardy
Ying Zhang, … , Jan van Deursen, Paul J. Galardy
Published November 26, 2012
Citation Information: J Clin Invest. 2012;122(12):4362-4374. https://doi.org/10.1172/JCI63084.
View: Text | PDF
Research Article Article has an altmetric score of 11

USP44 regulates centrosome positioning to prevent aneuploidy and suppress tumorigenesis

Abstract

Most human tumors have abnormal numbers of chromosomes, a condition known as aneuploidy. The mitotic checkpoint is an important mechanism that prevents aneuploidy by restraining the activity of the anaphase-promoting complex (APC). The deubiquitinase USP44 was identified as a key regulator of APC activation; however, the physiological importance of USP44 and its impact on cancer biology are unknown. To clarify the role of USP44 in mitosis, we engineered a mouse lacking Usp44. We found that USP44 regulated the mitotic checkpoint and prevented chromosome lagging. Mice lacking Usp44 were prone to the development of spontaneous tumors, particularly in the lungs. Additionally, USP44 was frequently downregulated in human lung cancer, and low expression correlated with a poor prognosis. USP44 inhibited chromosome segregation errors independent of its role in the mitotic checkpoint by regulating centrosome separation, positioning, and mitotic spindle geometry. These functions required direct binding to the centriole protein centrin. Our data reveal a new role for the ubiquitin system in mitotic spindle regulation and underscore the importance of USP44 in the pathogenesis of human cancer.

Authors

Ying Zhang, Oded Foreman, Dennis A. Wigle, Farhad Kosari, George Vasmatzis, Jeffrey L. Salisbury, Jan van Deursen, Paul J. Galardy

×

Figure 4

USP44 is required for proper centrosome separation and spindle geometry.

Options: View larger image (or click on image) Download as PowerPoint
USP44 is required for proper centrosome separation and spindle geometry....
(A) Confocal immunofluorescence microscopy was performed on MEFs of the indicated genotypes using antibodies against the indicated proteins. Scale bar:5 μm. (B) Incidence of spindle abnormalities in MEFs of the indicated genotypes. Graph represents the mean ± SEM for 3 lines per genotype, with at least n = 20 cells per line. (C) Comparison of the inter-pole distance, as defined as the distance between γ-tubulin–positive centrosomes, in metaphases with normal versus abnormal spindle geometry. Images collected by confocal immunofluorescence microscopy. Graph represents the mean ± SEM for n = 12–13 metaphases per group regardless of genotype. (D) MEFs were transduced with γ-tubulin–CFP and H2B-RFP and followed through unperturbed mitoses with live-cell microscopy. The inter-pole distance was calculated at nuclear envelope breakdown (NEBD) and the onset of anaphase in Usp44+/+ (n = 31) and Usp44–/– cells (n = 26), and the data are expressed as the ratio between these values. Graph represents the mean ± SEM for cells with normal (n = 45) versus abnormal (n = 14) chromosome segregation, regardless of genotype. (E) The incidence of incomplete centrosome separation (inter-pole distance at NEBD <75% that at anaphase onset) was determined in MEFs of the indicated genotype from B. The graph represents the percent incidence of cells with incomplete centrosome separation in the entire cohort of cells observed. (F and G) Examples of MEFs with normal or abnormal centrosome separation (F) or spindle geometry (G) as seen by live-cell microscopy. Scale bars: 5 μm. *P < 0.05, 2-tailed unpaired t test.