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Inducible expression of cyclin D1 in T‐47D human breast cancer cells is sufficient for Cdk2 activation and pRB hyperphosphorylation
Author(s) -
Musgrove Elizabeth A.,
Sarcevic Boris,
Sutherland Robert L.
Publication year - 1996
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19960301)60:3<363::aid-jcb8>3.0.co;2-u
Subject(s) - cyclin d , cyclin d1 , cyclin a2 , cyclin b , cyclin e , cyclin a , cancer research , cyclin dependent kinase complex , cyclin dependent kinase , cyclin dependent kinase 2 , biology , microbiology and biotechnology , retinoblastoma protein , cell cycle , kinase , protein kinase a , biochemistry , cell
The sequential transcriptional activation of cyclins, the regulatory subunits of cell cycle specific kinases, regulates progress through the cell cycle. In mitogen‐stimulated cells cyclin D1 induction in early G 1 is followed by induction of cyclin E, activation of the cyclin‐dependent kinase Cdk2, and hyperphosphorylation of the retinoblastoma gene product (pRB) in mid‐to‐late G 1 phase. T‐47D breast cancer cells expressing cyclin D1 under the control of a metal‐responsive metallothionein promoter were used to determine whether Cdk2 activation and pRB hyperphosphorylation are consequences of cyclin D1 induction. A 4–5‐fold increase in cyclin D1 protein abundance was followed by approximately 2‐fold increases in cyclin E protein abundance and Cdk2 activity and by hyperphosphorylation of pRB. These responses were apparent ∼ 3 h after the increase in cyclin D1 protein, and ∼ 3 h prior to the entry of cyclin D1‐stimulated cells into S phase 12 h after zinc treatment. Cyclin D1 immunoprecipitates contained Cdk4 but no detectable Cdk2 and displayed pRb but not histone H1 kinase activity. Cdk2 activation was therefore likely to be due to increased abundance of cyclin E/Cdk2 complexes rather than formation of active cyclin D1/Cdk2 complexes. The sequence of events following zinc induction of cyclin D1 thus mimicked that following mitogen induction of cyclin D1. These data show that cyclin D1 induction is sufficient for Cdk2 activation and pRB hyperphosphorylation in T‐47D human breast cancer cells, providing evidence that cyclin D1 induction is a critical event in G 1 phase progression. © 1996 Wiley‐Liss, Inc.