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Effect of PACT knockout on LNCaP protate cancer cells

ABSTRACT: PACT, encoded by the PRKRA gene, is a double-stranded RNA binding protein which has two main mechanisms of action; functioning as an activator of both protein kinase RNA (PKR) and retinoic acid-inducible gene 1 (RIG-1) to facilitate innate antiviral defense mechanisms in mammals; and PACT is also an integral member of the cytoplasmic RNA-induced silencing complex (RISC) which enables the processing of pre-microRNAs into mature microRNAs (miRNAs). We previously described an alternate role for PACT as a nuclear receptor (NR) co-activator, which when recruited to hormone-regulated promoters can modulate the expression of NR-regulated genes. Here we employed a loss of function approach to investigate the role of PACT in prostate cancer (PCa). Depletion of PACT in human PCa cell lines resulted in a significant reduction in cell proliferation. RNA-sequencing analysis of LNCaP PCa cells ± PACT revealed that in the absence of PACT, various biological processes involved in proliferation were depleted, including cell cycle progression and division.

ORGANISM(S): Homo sapiens

PROVIDER: GSE253245 | GEO | 2025/12/02

REPOSITORIES: GEO

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Long non-coding RNA DARS-AS1 promotes tumor progression by suppressing PACT-mediated PKR activation

Project description:Cancer cells evolve various mechanisms to overcome cellular stresses and maintain progression. Protein kinase R (PKR) and its protein activator (PACT) are the initial responders in monitoring diverse stress signals and lead to cell proliferation inhibition and cell apoptosis in consequence. However, the regulation of PACT-PKR pathway in cancer cells is largely unknown. Herein, we identify that the long non-coding RNA (lncRNA) aspartyl-tRNA synthetase antisense RNA 1 (DARS-AS1) is directly involved in the inhibition of the PACT-PKR pathway and promotes cancer cell proliferation. Using large-scale CRISPRi functional screening of 971 cancer-associated lncRNAs, we find that DARS-AS1 is associated with significantly enhanced cancer cell proliferation. Accordingly, knocking down DARS-AS1 inhibits cell proliferation of multiple cancer cell lines and promotes cancer cell apoptosis in vitro and significantly reduces tumor growth in vivo. Mechanistically, DARS-AS1 directly binds to the activator domain of PACT and prevents PACT-PKR interaction, thereby decreasing PKR activation, eIF2α phosphorylation and inhibiting apoptotic cell death. Clinically, DARS-AS1 is broadly expressed across multiple cancers and the increased expression of this lncRNA indicates poor prognosis. This study elucidates the lncRNA DARS-AS1 directed cancer-specific modulation of the PACT-PKR pathway and provides a novel target for cancer prognosis and therapeutic treatment.

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PACT suppresses PKR activation through dsRNA binding and dimerization, and is a therapeutic target for triple-negative breast cancer

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Project description:The RIG-I-like receptors (RLRs: RIG-I, MDA5 and LGP2) trigger inflammatory and antiviral responses by sensing non-self RNA molecules produced during viral replication. LGP2 regulation of RIG-I and MDA5-dependant type-I interferon signaling is a matter of controversy. Here we show that LGP2 interacts with different components of the RNA silencing machinery. Particularly, we identified a direct protein-protein interaction between LGP2 and interferon-inducible double-stranded RNA-dependent protein kinase activator A (PACT). The LGP2-PACT interaction is mediated by the regulatory C-terminal domain of LGP2 and is necessary for inhibiting the RIG-I- and amplifying the MDA5-responses. We describe a point mutation within LGP2 that disrupts LGP2-PACT interaction and leads to the loss of LGP2 regulatory activity over RIG-I and MDA5. These results provide a model in which PACT-LGP2 interaction regulates RIG-I and MDA5 inflammatory response and allows cellular RNA silencing machinery to coordinate the innate immune response.

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Deletion of human tarbp2 reveals cellular microRNA targets and cell cycle function of TRBP

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PACT-mediated regulation of endogenous dsRNA sensing by PKR

Project description:PACT-mediated regulation of endogenous dsRNA sensing by PKR

| PRJNA1123226 | ENA

Deletion of human tarbp2 reveals cellular microRNA targets and cell cycle function of TRBP

2014-09-16 | GSE61458 | GEO

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