The nucleolar phosphataseCdc14Bis dispensable for chromosome segregation and mitotic exit in human cells

Abstract

In yeast, the protein phosphatase Cdc14 promotes chromosome segregation, mitotic exit, and cytokinesis by reversing M-phase phosphorylations catalyzed by Cdk1. A key feature of Cdc14 regulation is its sequestration within the nucleolus, which restricts its access to potential substrates for much of the cell cycle. Mammals also possess a nucleolar Cdc14 homolog, termed Cdc14B, but its roles during mitosis and cell division remain speculative. Here we analyze Cdc14B's subcellular dynamics during mitosis and rigorously test its functional contributions to cell division through homozygous disruption of the Cdc14B locus in human somatic cells. While Cdc14B is initially released from nucleoli at the start of mitosis, the phosphatase quickly redistributes onto segregating sister chromatids during anaphase. This relocalization is mainly driven by Cdk1 inactivation, as pharmacologic inhibition of Cdk1 in prometaphase cells redirects Cdc14B onto chromosomes. However, in sharp contrast to yeast cdc14 mutants, human Cdc14B Δ/Δ cells were viable and lacked defects in spindle assembly, anaphase progression, mitotic exit, and cytokinesis, and continued to segregate ribosomal DNA repeats with near-normal proficiency. Our findings reveal substantial divergence in mitotic regulation between yeast and mammalian cells, as the latter possess efficient mechanisms for completing late M-phase events in the absence of a nucleolar Cdc14-related phosphatase.

Human phosphatase CDC14A is recruited to the cell leading edge to regulate cell migration and adhesion

“…Consistent with previous reports of hCDC14 KO cells (22,28), the hCDC14A PD cells were viable. Flow cytometry (FACS) comparisons with WT cells revealed no significant differences in the distribution of cell cycle phases in hCDC14A PD (Fig.…”

“…Unlike budding yeast CDC14, neither human hCDC14A nor hCDC14B are essential for either cell viability or mitotic exit (22,28). Rather, hCDC14A has functions outside cell cycle regulation.…”

p53- and p21-dependent premature APC/C–Cdh1 activation in G2 is part of the long-term response to genotoxic stress

“…Recently, a Cdc14B-knockout HCT116 derivative has been presented (Berdougo et al, 2008). The same factor was previously shown to be required for premature APC/C activation in doxorubicin-treated U2OS cells, by using an short interfering RNA-based knockdown approach (Bassermann et al, 2008).…”

Cell cycle control of spindle elongation

“…While fission yeast and C. elegans also rely to some extent on Cdc14 homologues, 68-72 the majority of eukaryotes do not need Cdc14 for mitotic exit. 73,74 A systematic RNAi screen in Drosophila S2 cells revealed that several phosphatases are required to progress through and exit mitosis. 75 In Xenopus egg extracts PP1, PP2A and calcineurin have been shown to oppose the Cdk1 activity.…”