Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component: Association with inhibition of p27 accumulation

Hangjun Duan, Lyuben M. Tsvetkov, Yalun Liu, Ying Song, Manju Swaroop, Rong Wen, Hsiang Fu Kung, Hui Zhang, Yi Sun

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [3H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10-to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation.

Original languageEnglish
Pages (from-to)37-46
Number of pages10
JournalMolecular Carcinogenesis
Volume30
Issue number1
DOIs
StatePublished - Feb 19 2001
Externally publishedYes

Fingerprint

Ubiquitin-Protein Ligases
Starvation
S Phase
Apoptosis
Growth
Serum
Genes
Inhibition (Psychology)
Human Adenovirus Infections
Cullin Proteins
F-Box Proteins
Cyclin-Dependent Kinase Inhibitor p21
NIH 3T3 Cells
Proteasome Inhibitors
Cyclin-Dependent Kinases
Ubiquitination
Microinjections
Ubiquitin
Neuroblastoma
Keratinocytes

Keywords

  • Cell growth
  • p27
  • RING finger
  • SAG/ROC/Rbx/Hrt
  • Serum starvation
  • Ubiquitin ligase

ASJC Scopus subject areas

  • Cancer Research
  • Molecular Biology

Cite this

Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component : Association with inhibition of p27 accumulation. / Duan, Hangjun; Tsvetkov, Lyuben M.; Liu, Yalun; Song, Ying; Swaroop, Manju; Wen, Rong; Kung, Hsiang Fu; Zhang, Hui; Sun, Yi.

In: Molecular Carcinogenesis, Vol. 30, No. 1, 19.02.2001, p. 37-46.

Research output: Contribution to journalArticle

Duan, Hangjun ; Tsvetkov, Lyuben M. ; Liu, Yalun ; Song, Ying ; Swaroop, Manju ; Wen, Rong ; Kung, Hsiang Fu ; Zhang, Hui ; Sun, Yi. / Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component : Association with inhibition of p27 accumulation. In: Molecular Carcinogenesis. 2001 ; Vol. 30, No. 1. pp. 37-46.
@article{66f90f52b3f84b2bb4bf0c7fe74784e1,
title = "Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component: Association with inhibition of p27 accumulation",
abstract = "The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [3H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10-to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation.",
keywords = "Cell growth, p27, RING finger, SAG/ROC/Rbx/Hrt, Serum starvation, Ubiquitin ligase",
author = "Hangjun Duan and Tsvetkov, {Lyuben M.} and Yalun Liu and Ying Song and Manju Swaroop and Rong Wen and Kung, {Hsiang Fu} and Hui Zhang and Yi Sun",
year = "2001",
month = "2",
day = "19",
doi = "10.1002/1098-2744(200101)30:1<37::AID-MC1011>3.0.CO;2-7",
language = "English",
volume = "30",
pages = "37--46",
journal = "Molecular Carcinogenesis",
issn = "0899-1987",
publisher = "Wiley-Liss Inc.",
number = "1",

}

TY - JOUR

T1 - Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component

T2 - Association with inhibition of p27 accumulation

AU - Duan, Hangjun

AU - Tsvetkov, Lyuben M.

AU - Liu, Yalun

AU - Song, Ying

AU - Swaroop, Manju

AU - Wen, Rong

AU - Kung, Hsiang Fu

AU - Zhang, Hui

AU - Sun, Yi

PY - 2001/2/19

Y1 - 2001/2/19

N2 - The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [3H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10-to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation.

AB - The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [3H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10-to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation.

KW - Cell growth

KW - p27

KW - RING finger

KW - SAG/ROC/Rbx/Hrt

KW - Serum starvation

KW - Ubiquitin ligase

UR - http://www.scopus.com/inward/record.url?scp=0035143141&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035143141&partnerID=8YFLogxK

U2 - 10.1002/1098-2744(200101)30:1<37::AID-MC1011>3.0.CO;2-7

DO - 10.1002/1098-2744(200101)30:1<37::AID-MC1011>3.0.CO;2-7

M3 - Article

C2 - 11255262

AN - SCOPUS:0035143141

VL - 30

SP - 37

EP - 46

JO - Molecular Carcinogenesis

JF - Molecular Carcinogenesis

SN - 0899-1987

IS - 1

ER -