Functional interactions of the retinoblastoma protein with mammalian D-type cyclins

ME Ewen, HK Sluss, CJ Sherr, H Matsushime, J Kato… - Cell, 1993 - cell.com
ME Ewen, HK Sluss, CJ Sherr, H Matsushime, J Kato, DM Livingston
Cell, 1993cell.com
The retinoblastoma gene product (Rb) can interact eff iciently with two of three D-type G,
cyclins (D2 and D3) in vitro. Binding depended upon the minimal regions of Rb necessary
for its growth-suppressive activity, as well as upon the D-type cyclin sequence motif shared
with W-binding DNA tumor virus oncoproteins. Coexpression of the three D-type cyclins with
the cyclln-dependent klnase (cdk4) in insect cells generated Rb klnase activity. By contrast,
cyclins D2 and 03, but not Dl, activated another such klnase, cdk2. Introduction of cyclin 02 …
Summary
The retinoblastoma gene product (Rb) can interact eff iciently with two of three D-type G, cyclins (D2 and D3) in vitro. Binding depended upon the minimal regions of Rb necessary for its growth-suppressive activity, as well as upon the D-type cyclin sequence motif shared with W-binding DNA tumor virus oncoproteins. Coexpression of the three D-type cyclins with the cyclln-dependent klnase (cdk4) in insect cells generated Rb klnase activity. By contrast, cyclins D2 and 03, but not Dl, activated another such klnase, cdk2. Introduction of cyclin 02 and Rb into the Rb-deficient cell line SAOS-2 led to overt Rb hyperphosphorylation, whereas Rb, expressed alone or together with cyclin Dl, remained unphosphorylated. Cyclln DS-dependent phosphorylation inhibited its binding to the transcription factor E2F and reversed the Rb G, exit block in the cell cycle. Thus, all D-type cyclins do not function equivalently, and one of them plays a major role in reversing the cycle-blocking function of a known tumor suppressor.
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