Yeast homolog of human SAG/ROC2/Rbx2/Hrt2 is essential for cell growth, but not for germination: chip profiling implicates its role in cell cycle regulation

Swaroop, Manju; Wang, Yixin; Miller, Paul; Duan, Hangjun; Jatkoe, Tim; Madore, Steven J.; Sun, Yi

doi:10.1038/sj.onc.1203635

Cited by 63 publications

(77 citation statements)

References 83 publications

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“…Earlier studies have shown that Hrt1, the yeast homologue of RBX1, is a growth essential gene whose targeted disruption causes yeast death, which can be rescued by either human RBX1 (3,6) or its family member, RBX2/SAG (31). In Caenorhabditis elegans, siRNA knockdown of RBX1 causes pronounced defects in the first meiotic division, in mitotic chromosomal condensation, and in germ cell proliferation, indicating its role in chromosome metabolism and cell cycle control (32).…”

Section: Primary Mef Cells (C) or Es Cells (D)mentioning

confidence: 99%

RBX1/ROC1 disruption results in early embryonic lethality due to proliferation failure, partially rescued by simultaneous loss of p27

Tan

Davis

Saunders

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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RBX1 (RING box protein-1) or ROC1 (regulator of cullins-1) is the RING component of SCF (Skp1, Cullins, F-box proteins) E3 ubiquitin ligases, which regulate diverse cellular processes by targeting various substrates for degradation. However, the in vivo physiological function of RBX1 remains uncharacterized. Here, we show that a gene trap disruption of mouse Rbx1 causes embryonic lethality at embryonic day (E)7.5, mainly due to a failure in proliferation; p27, a cyclin dependent kinase inhibitor, normally undetectable in the early embryos, accumulates at high levels in the absence of Rbx1. Although mice heterozygous for the Rbx1 gene trap appear viable and fertile without obvious abnormalities, the Rbx1 ؉/Gt MEFs do show retarded growth with G1 arrest and p27 accumulation. Simultaneous loss of p27 extended the life span of Rbx1 Gt/Gt embryos from E6.5 to E9.5, indicating that p27-mediated cell cycle inhibition contributes to the early embryonic lethality in the Rbx1-deficient embryos. Our study demonstrates that the in vivo physiological function of RBX1 is to ensure cell proliferation by preventing p27 accumulation during the early stage of embryonic development.SCF E3 ubiquitin ligase ͉ protein degradation ͉ growth suppression

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Section: Primary Mef Cells (C) or Es Cells (D)mentioning

confidence: 99%

RBX1/ROC1 disruption results in early embryonic lethality due to proliferation failure, partially rescued by simultaneous loss of p27

Tan

Davis

Saunders

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…In yeast, deletion of Hrt1, the yeast homolog of RBX1, causes lethality, which can be rescued by human RBX1 or RBX2/SAG (Sensitive to Apoptosis gene) (9,12,13). In Caenorhabditis elegans, RBX-1 is crucial for cell cycle progression and chromosome metabolism, and RBX-1 silencing results in embryonic death (14,15).…”

mentioning

confidence: 99%

RBX1 (RING Box Protein 1) E3 Ubiquitin Ligase Is Required for Genomic Integrity by Modulating DNA Replication Licensing Proteins

Jia

Bickel

et al. 2011

Journal of Biological Chemistry

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RBX1 (RING box protein 1), also known as ROC1 (Regulator of Cullin 1), is an essential component of SCF (Skp1/Cullins/Fbox) E3 ubiquitin ligases, which target diverse proteins for proteasome-mediated degradation. Our recent study showed that RBX1 silencing triggered a DNA damage response (DDR) leading to G 2 -M arrest, senescence, and apoptosis, with the mechanism remaining elusive. Here, we show that, in human cancer cells, RBX1 silencing causes the accumulation of DNA replication licensing proteins CDT1 and ORC1, leading to DNA double-strand breaks, DDR, G 2 arrest, and, eventually, aneuploidy. Whereas CHK1 activation by RBX1 silencing is responsible for the G 2 arrest, enhanced DNA damage renders cancer cells more sensitive to radiation. In Caenorhabditis elegans, RBX-1 silencing causes CDT-1 accumulation, triggering DDR in intestinal cells, which is largely abrogated by simultaneous CDT-1 silencing. RBX-1 silencing also induces lethality during development of embryos and in adulthood. Thus, RBX1 E3 ligase is essential for the maintenance of mammalian genome integrity and the proper development and viability in C. elegans. SCF (Skp1/Cullins/F-box; also known as CRL (Cullin-RING Ligase) E3 ubiquitin ligases are the largest multiunit E3 ligases that promote the degradation of numerous short-lived cellular proteins, including cell cycle regulators, transcription factors, signal transducers, and oncogene/tumor suppressors (1, 2). A recent global protein stability profiling analysis identified ϳ350 potential SCF substrates, the majority of which were previously unidentified (3). Most recently, a study of SCF inactivation by a small molecule inhibitor of cullin neddylation suggested that up to 20% of ubiquitinated cellular proteins are mediated by SCF E3 for proteasome degradation (4). Thus, SCF E3 ubiquitin ligases regulate many aspects of cellular functions and biological processes under physiological conditions. Dysfunction of SCF is involved in the pathogenesis of a variety of diseases, including cancer (2, 5).The core of SCF ubiquitin ligases is a complex of RBX1-cullins (6). RBX1 consists of 108 amino acids with a C-terminal RING-H2 finger domain required for zinc ion binding and ligase activity (7-9). Crystal structure studies revealed that RBX1 complexes with cullin/F-box proteins form functional SCF E3 ligases that transfer ubiquitin from E2 to specific substrates for proteasome-targeted degradation (10). Previous studies have shown that RBX1 interacts with all seven cullin family members to activate E3 ubiquitin ligases and regulate numerous biological processes by promoting timely degradation of cellular substrates (9, 11).As an essential component of SCF E3 ligase, RBX1 plays a critical role in development. In yeast, deletion of Hrt1, the yeast homolog of RBX1, causes lethality, which can be rescued by human RBX1 or RBX2/SAG (Sensitive to Apoptosis gene) (9,12,13). In Caenorhabditis elegans, RBX-1 is crucial for cell cycle progression and chromosome metabolism, and RBX-1 silencing results in embryonic d...

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“…RBX1 was initially identified as an essential protein for the full activity of SKP1-Cul1-F-Box protein (SCF) E3 ligase, also known as CRL-1, the founding member of CRL (10)(11)(12)(13). SAG, originally cloned in our laboratory, is a redox-inducible antioxidant protein (14) that was later characterized as the second member of the RBX/ROC RING component in SCF/CRL E3s (15). Although RBX1 and SAG are biochemically interchangeable in carrying out E3 ligase activity (15,16), the in vivo physiological functions of both family members was found to be nonredundant.…”

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confidence: 99%

Inactivation of SAG/RBX2 E3 ubiquitin ligase suppresses KrasG12D-driven lung tumorigenesis

Tan

Jia

et al. 2014

J. Clin. Invest.

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Cullin-RING ligases (CRLs) are a family of E3 ubiquitin ligase complexes that rely on either RING-box 1 (RBX1) or sensitive to apoptosis gene (SAG), also known as RBX2, for activity. RBX1 and SAG are both overexpressed in human lung cancer; however, their contribution to patient survival and lung tumorigenesis is unknown. Here, we report that overexpression of SAG, but not RBX1, correlates with poor patient prognosis and more advanced disease. We found that SAG is overexpressed in murine Kras G12D -driven lung tumors and that Sag deletion suppressed lung tumorigenesis and extended murine life span. Using cultured lung cancer cells, we showed that SAG knockdown suppressed growth and survival, inactivated both NF-κB and mTOR pathways, and resulted in accumulation of tumor suppressor substrates, including p21, p27, NOXA, and BIM. Importantly, growth suppression by SAG knockdown was partially rescued by simultaneous knockdown of p21 or the mTOR inhibitor DEPTOR. Treatment with MLN4924, a small molecule inhibitor of CRL E3s, also inhibited the formation of Kras G12D -induced lung tumors through a similar mechanism involving inactivation of NF-κB and mTOR and accumulation of tumor suppressor substrates. Together, our results demonstrate that Sag is a Kras-cooperating oncogene that promotes lung tumorigenesis and suggest that targeting SAG-CRL E3 ligases may be an effective therapeutic approach for Kras-driven lung cancers.

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Yeast homolog of human SAG/ROC2/Rbx2/Hrt2 is essential for cell growth, but not for germination: chip profiling implicates its role in cell cycle regulation

Cited by 63 publications

References 83 publications

RBX1/ROC1 disruption results in early embryonic lethality due to proliferation failure, partially rescued by simultaneous loss of p27

RBX1/ROC1 disruption results in early embryonic lethality due to proliferation failure, partially rescued by simultaneous loss of p27

RBX1 (RING Box Protein 1) E3 Ubiquitin Ligase Is Required for Genomic Integrity by Modulating DNA Replication Licensing Proteins

Inactivation of SAG/RBX2 E3 ubiquitin ligase suppresses KrasG12D-driven lung tumorigenesis

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