Acute Ablation of Survivin Uncovers p53-dependent Mitotic Checkpoint Functions and Control of Mitochondrial Apoptosis

Abstract

Survivin is a member of the Inhibitor of Apoptosis gene family that has been implicated in cell division and suppression of apoptosis. Here, we show that preferential ablation of the nuclear pool of survivin by RNA interference produces a mitotic arrest followed by re-entry into the cell cycle and polyploidy. Survivin ablation causes multiple centrosomal defects, aberrant multipolar spindle formation, and chromatin missegregation, and these phenotypes are exacerbated by loss of the cell cycle regulator, p21Waf1/Cip1 in p21 ؊/؊ cells. The mitotic checkpoint activated by loss of survivin is mediated by induction of p53 and associated with increased expression of its downstream target, p21 Waf1/Cip1. Accordingly, p53؊/؊ cells exhibit reduced mitotic arrest and enhanced polyploidy upon survivin ablation as compared with their p53 ؉/؉ counterparts. Partial reduction of the cytosolic pool of survivin by RNA interference sensitizes cells to ultraviolet B-mediated apoptosis and results in enhanced caspase-9 proteolytic cleavage, whereas complete ablation of cytosolic survivin causes loss of mitochondrial membrane potential and spontaneous apoptosis. These data demonstrate that survivin has separable checkpoint functions at multiple phases of mitosis and in the control of mitochondrial-dependent apoptosis.

Differential regulation of survivin by p53 contributes to cell cycle dependent apoptosis

“…Survivin, a member of the inhibitor of apoptosis protein (IAP) family, has been revealed to participate the control of apoptosis and G 2 /M checkpoint [3,44,45]. It was reported that the expression of survivin was at low level in G 1 and S phase but was elevated in G 2 /M phase, and this G 2 /M specific expression has been related to mitotic spindle checkpoint function [3].…”

Transcriptional activation of cyclooxygenase-2 by tumor suppressor p53 requires nuclear factor-kappaB

“…In non-small-cell lung cancer cell lines, genetic or pharmacological inhibition of Cox-2 enhances proteosomal degradation of the inhibitor of apoptosis survivin (Beltrami et al, 2004;Krysan et al, 2004a, b). In turn, depletion of survivin causes arrest of DNA synthesis owing to activation of p53 and p21 WafÀ1 (Beltrami et al, 2004;Yang et al, 2004). Thus, in tumor cells with wildtype p53, inhibition of Cox-2 may result in increased p53-dependent growth suppression.…”

Centrosome amplification induced by survivin suppression enhances both chromosome instability and radiosensitivity in glioma cells

“…It inhibits apoptosis (Altieri, 2001) and is involved in the spindle checkpoint and the regulation of proper chromosomal segregation during mitosis by acting as a member of the chromosomal passenger protein family (Li et al, 1998;Adams et al, 2001). A number of studies have demonstrated that the suppression of survivin results in cells with multipolar mitotic spindles that are either multinucleated or aneuploid (Li et al, 1999;Beltrami et al, 2004;Kappler et al, 2004). Some studies have also indicated that aneuploidy promotes chromosome instability (CIN) in glioma and cervical carcinoma cells (Nitta et al, 2002;Olaharski et al, 2006).…”