Transforming growth factor β targeted inactivation of cyclin E:cyclin-dependent kinase 2 (Cdk2) complexes by inhibition of Cdk2 activating kinase activity
Nagahara, Hikaru ; Ezhevsky, Sergei A. ; Vocero-Akbani, Adamina M. ; Kaldis, Philipp LU
; Solomon, Mark J.
and Dowdy, Steven F.
(1999)
In Proceedings of the National Academy of Sciences of the United States of America
96(26).
p.14961-14966
- Abstract
Transforming growth factor β (TGF-β)-mediated G1 arrest previously has been shown to specifically target inactivation of cyclin D:cyclin-dependent kinase (Cdk) 4/6 complexes. We report here that TGF-β-treated human HepG2 hepatocellular carcinoma cells arrest in G1, but retain continued cyclin D:Cdk4/6 activity and active, hypophosphorylated retinoblastoma tumor suppressor protein. Consistent with this observation, TGF-β-treated cells failed to induce p15INK4b, down-regulate CDC25A, or increase levels of p21CIP1, p27KIP1, and p57KIP2. However, TGF-β treatment resulted in the specific inactivation of cyclin E:Cdk2 complexes caused by absence of the activating... (More)
Transforming growth factor β (TGF-β)-mediated G1 arrest previously has been shown to specifically target inactivation of cyclin D:cyclin-dependent kinase (Cdk) 4/6 complexes. We report here that TGF-β-treated human HepG2 hepatocellular carcinoma cells arrest in G1, but retain continued cyclin D:Cdk4/6 activity and active, hypophosphorylated retinoblastoma tumor suppressor protein. Consistent with this observation, TGF-β-treated cells failed to induce p15INK4b, down-regulate CDC25A, or increase levels of p21CIP1, p27KIP1, and p57KIP2. However, TGF-β treatment resulted in the specific inactivation of cyclin E:Cdk2 complexes caused by absence of the activating Thr160 phosphorylation on Cdk2. Whole-cell lysates from TGF-β-treated cells showed inhibition of Cdk2 Thr160 Cdk activating kinase (CAK) activity; however, cyclin H:Cdk7 activity, a previously assumed mammalian CAK, was not altered. Saccharomyces cerevisiae contains a genetically and biochemically proven CAK gene, CAK1, that encodes a monomeric 44-kDa Cak1p protein unrelated to Cdk7. Anti-Cak1p antibodies cross-reacted with a 45-kDa human protein with CAK activity that was specifically down-regulated in response to TGF-β treatment. Taken together, these observations demonstrate that TGF-β signaling mediates a G1 arrest in HepG2 cells by targeting Cdk2 CAK and suggests the presence of at least two mammalian CAKs: one specific for Cdk2 and one for Cdk4/6.
(Less)
- author
- Nagahara, Hikaru
; Ezhevsky, Sergei A.
; Vocero-Akbani, Adamina M.
; Kaldis, Philipp
LU
; Solomon, Mark J.
and Dowdy, Steven F.
- publishing date
- 1999-12-21
- type
- Contribution to journal
- publication status
- published
- in
- Proceedings of the National Academy of Sciences of the United States of America
- volume
- 96
- issue
- 26
- pages
- 14961 - 14966
- publisher
- National Academy of Sciences
- external identifiers
-
- scopus:0033593055
- pmid:10611320
- ISSN
- 0027-8424
- DOI
- 10.1073/pnas.96.26.14961
- language
- English
- LU publication?
- no
- id
- 01fb7e0a-e363-47d4-bc5f-a6db6ade8403
- date added to LUP
- 2019-09-18 14:33:30
- date last changed
- 2024-01-01 20:48:07
@article{01fb7e0a-e363-47d4-bc5f-a6db6ade8403,
abstract = {{<p>Transforming growth factor β (TGF-β)-mediated G<sub>1</sub> arrest previously has been shown to specifically target inactivation of cyclin D:cyclin-dependent kinase (Cdk) 4/6 complexes. We report here that TGF-β-treated human HepG2 hepatocellular carcinoma cells arrest in G<sub>1</sub>, but retain continued cyclin D:Cdk4/6 activity and active, hypophosphorylated retinoblastoma tumor suppressor protein. Consistent with this observation, TGF-β-treated cells failed to induce p15<sup>INK4b</sup>, down-regulate CDC25A, or increase levels of p21<sup>CIP1</sup>, p27<sup>KIP1</sup>, and p57<sup>KIP2</sup>. However, TGF-β treatment resulted in the specific inactivation of cyclin E:Cdk2 complexes caused by absence of the activating Thr<sup>160</sup> phosphorylation on Cdk2. Whole-cell lysates from TGF-β-treated cells showed inhibition of Cdk2 Thr<sup>160</sup> Cdk activating kinase (CAK) activity; however, cyclin H:Cdk7 activity, a previously assumed mammalian CAK, was not altered. Saccharomyces cerevisiae contains a genetically and biochemically proven CAK gene, CAK1, that encodes a monomeric 44-kDa Cak1p protein unrelated to Cdk7. Anti-Cak1p antibodies cross-reacted with a 45-kDa human protein with CAK activity that was specifically down-regulated in response to TGF-β treatment. Taken together, these observations demonstrate that TGF-β signaling mediates a G<sub>1</sub> arrest in HepG2 cells by targeting Cdk2 CAK and suggests the presence of at least two mammalian CAKs: one specific for Cdk2 and one for Cdk4/6.</p>}},
author = {{Nagahara, Hikaru and Ezhevsky, Sergei A. and Vocero-Akbani, Adamina M. and Kaldis, Philipp and Solomon, Mark J. and Dowdy, Steven F.}},
issn = {{0027-8424}},
language = {{eng}},
month = {{12}},
number = {{26}},
pages = {{14961--14966}},
publisher = {{National Academy of Sciences}},
series = {{Proceedings of the National Academy of Sciences of the United States of America}},
title = {{Transforming growth factor β targeted inactivation of cyclin E:cyclin-dependent kinase 2 (Cdk2) complexes by inhibition of Cdk2 activating kinase activity}},
url = {{http://dx.doi.org/10.1073/pnas.96.26.14961}},
doi = {{10.1073/pnas.96.26.14961}},
volume = {{96}},
year = {{1999}},
}