CPEB (Cytoplasmic Polyadenylation Element Binding) proteins are a family of four 
RNA-binding proteins that regulate the translation of maternal mRNAs controlling 
meiotic cell cycle progression. But CPEBs are not limited to the 
transcriptionally silent germline; they are also expressed, in various 
combinations, in somatic cells, yet their role in regulation of mitosis-related 
gene expression is largely unknown. Deregulation of CPEB1 and CPEB4 have been 
linked to tumor development. However, a systematic analysis addressing their 
requirements for the temporal regulation of mitotic gene expression has yet to 
be performed. This study addresses the requirements of each of the four CPEBs 
for mitotic phase transitions, with a particular focus on cytoplasmic 
polyadenylation and translational regulation. We demonstrate that CPEB3 is the 
only member dispensable for mitotic cell division, whereas the other three 
members, CPEB1, 2, and 4, are essential to successful mitotic cell division. 
Thus, CPEB1 is required for prophase entry, CPEB2 for metaphase and CPEB4 for 
cytokinesis. These three CPEBs have sequential non-redundant functions that 
promote the phase-specific polyadenylation and translational activation of 
CPE-regulated transcripts in the mitotic cell cycle.