Functional expression cloning reveals proapoptotic role for protein phosphatase 4

Abstract

Functional expression cloning strategies are highly suitable for the analysis of the molecular control of apoptosis. This approach has two critical advantages. Firstly, it eliminates prior assumptions about the properties of the proteins involved, and, secondly, it selectively targets proteins that are causally involved in apoptosis control and which affect the crucial cellular decision between survival and death. The application of this strategy to the isolation of cDNAs conferring resistance to dexamethasone and c-irradiation resulted in the isolation of a partial cDNA for the catalytic subunit of protein phosphatase 4 (PP4). Cells transfected with this partial cDNA in an expression vector downregulated PP4 and were resistant to both dexamethasone and UV radiation, as demonstrated by both membrane integrity and colonyforming assays. These observations suggest that PP4 plays an important proapoptotic role in T lymphocytes.

GAS5, a non-protein-coding RNA, controls apoptosis and is downregulated in breast cancer

“…Overexpression of Gas5 enhances stimulation of W7.2c cell apoptosis by UV and dexamethasone The apoptosis-sensitive W7.2c mouse thymoma cell subclone (Danielsen et al, 1983;Mourtada-Maarabouni et al, 2003a) was originally the host cell for isolation of a partial sequence of Gas5 in the functional screen for genes controlling apoptosis . We therefore examined the effects of expression of a Gas5 expressed sequence tag (EST) in this cell line.…”

“…The key advantage of this strategy is that it identifies those genes that play a causal role in the cell death process, and distinguishes this crucial group of genes from those that are differentially expressed but do not affect the cell death/survival decision (Sutherland et al, 2000;Mourtada-Maarabouni et al, 2002, 2003a, b, 2004, 2005Williams et al, 2006; reviewed in Williams and Farzaneh, 2004).…”

Protein phosphatase PP4 is overexpressed in human breast and lung tumors

“…Protein phosphatases 4 catalytic subunit (PP4C) plays an important role in microtubule growth/organization [2], apoptosis [3,4], tumor necrosis factor signaling [5], and pre-T-cell receptor signaling [4]. The ablation of PP4 leads to embryonic lethality in mice [4].…”

Regulation of apoptosis by fau revealed by functional expression cloning and antisense expression

“…The identification of many molecules involved in lymphocyte function (Starr et al, 1997), lymphomas and other cancers (Li et al, 1997;Lund et al, 2002;Mikkers et al, 2002;Suzuki et al, 2002) has highlighted the success of this approach. Notable successes have also been achieved by using this approach in identifying novel apoptosis controlling genes such as LUCA15/RBM5 novel tumour suppressor gene (Sutherland et al, 2000), protein phosphatase 4 (Mourtada-Maarabouni et al, 2003) and vATPase subunit E (Anderson and . In this study, we report the isolation of fau (Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV)-associated ubiquitously expressed gene) by functional expression cloning and its identification as an apoptosis regulatory gene.…”