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| Original Paper |
| Site-specific and temporally-regulated retinoblastoma protein dephosphorylation by protein phosphatase type 1 |
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| Ethel Rubin1, Sibylle Mittnacht2, Emma Villa-Moruzzi3 and John W Ludlow1,4 |
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1Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York, NY 14642, USA
2Department of Cell and Molecular Biology, Institute of Cancer Research, UK
3Department of Experimental Pathology, University of Pisa, Pisa, Italy
4University of Rochester Cancer Center, Rochester, New York, NY 14642, USA
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Correspondence to: J W Ludlow, Incara Pharmaceuticals, PO Box 14287, Research Triangle Park, North Carolina, NC 27709, USA; E-mail: JLudlow@incara.com
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| Abstract |
| pRb is dephosphorylated at mitotic exit by the type 1 serine/threonine protein phosphatases (PP1). Here we demonstrate for the first time that mitotic pRb dephosphorylation is a sequential, temporally-regulated event. We also provide evidence that the three mammalian isoforms of PP1,  ,  -1, and  , differ in their respective preferences for site-specific pRb dephosphorylation and that the mitotic and G1 PP1-isoform counterparts exhibit differential activities towards mitotic pRb. Finally, the physiological relevance of the striking contrast between the patterns of Thr821 and Thr826 dephosphorylation, sites known to be important for disrupting binding of LXCXE-containing proteins to pRb, is addressed. Oncogene (2001) 20, 3776-3785. |
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| Keywords |
| retinoblastoma protein; protein phosphatase type 1; pRB dephosphorylation; PP1 activity |
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| Received 29 January 2001; revised 3 April 2001; accepted 9 April 2001 |
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| 28 June 2001, Volume 20, Number 29, Pages 3776-3785 |
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