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 language | English |
|---|---|
| Pages (from-to) | 37-46 |
| Number of pages | 10 |
| Journal | Molecular Carcinogenesis |
| Volume | 30 |
| Issue number | 1 |
| DOIs | |
| State | Published - Feb 19 2001 |
| Externally published | Yes |
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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 journal › Article
}
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
VL - 30
SP - 37
EP - 46
JO - Molecular Carcinogenesis
JF - Molecular Carcinogenesis
SN - 0899-1987
IS - 1
ER -