Loss of HNRNP E1-dependent regulation of CDC27 translation leads to constitutive CDC27 expression, resulting in mitotic aberrations and aneuploidy in NMuMG cells. Confocal immunofluorescence microscopy was performed on fixed, asynchronous NMuMG cells constitutively expressing CDC27 (NMuMG-CDC27) using anti-alpha tubulin, anti-HNRNP E1, and DAPI to visualize mitoses. Mitotic aberrations were observed in NMuMG-CDC27 cells, while parental control cells exhibited normal mitoses, suggesting that cell cycle–dependent regulation of CDC27 expression is important in maintaining genomic integrity. For more information, see the article by Link and colleagues beginning on page 634.