TY - JOUR
T1 - Cyclin-dependent kinase-mediated phosphorylation plays a critical role in the oncogenic functions of PELP1
AU - Nair, Binoj C.
AU - Nair, Sujit S.
AU - Chakravarty, Dimple
AU - Challa, Rambabu
AU - Manavathi, Bramanandam
AU - Yew, P. Renee
AU - Kumar, Rakesh
AU - Tekmal, Rajeshwar Rao
AU - Vadlamudi, Ratna K.
PY - 2010/9/15
Y1 - 2010/9/15
N2 - Estrogen receptor (ER) signaling plays an important role in breast cancer progression, and ER functions are influenced by coregulatory proteins. PELP1 (proline-, glutamic acid-, and leucine-rich protein 1) is a nuclear receptor coregulator that plays an important role in ER signaling. Its expression is deregulated in hormonal cancers. We identified PELP1 as a novel cyclin-dependent kinase (CDK) substrate. Using site-directed mutagenesis and in vitro kinase assays, we identified Ser477 and Ser991 of PELP1 as CDK phosphorylation sites. Using the PELP1 Ser991 phospho-specific antibody, we show that PELP1 is hyperphosphorylated during cell cycle progression. Model cells stably expressing the PELP1 mutant that lack CDK sites had defects in estradiol (E2)-mediated cell cycle progression and significantly affected PELP1-mediated oncogenic functions in vivo. Mechanistic studies showed that PELP1 modulates transcription factor E2F1 transactivation functions, that PELP1 is recruited to pRb/E2F target genes, and that PELP1 facilitates ER signaling cross talk with cell cycle machinery. We conclude that PELP1 is a novel substrate of interphase CDKs and that its phosphorylation is important for the proper function of PELP1 in modulating hormone-driven cell cycle progression and also for optimal E2F transactivation function. Because the expression of both PELP1 and CDKs is deregulated in breast tumors, CDK-PELP1 interactions will have implications in breast cancer progression.
AB - Estrogen receptor (ER) signaling plays an important role in breast cancer progression, and ER functions are influenced by coregulatory proteins. PELP1 (proline-, glutamic acid-, and leucine-rich protein 1) is a nuclear receptor coregulator that plays an important role in ER signaling. Its expression is deregulated in hormonal cancers. We identified PELP1 as a novel cyclin-dependent kinase (CDK) substrate. Using site-directed mutagenesis and in vitro kinase assays, we identified Ser477 and Ser991 of PELP1 as CDK phosphorylation sites. Using the PELP1 Ser991 phospho-specific antibody, we show that PELP1 is hyperphosphorylated during cell cycle progression. Model cells stably expressing the PELP1 mutant that lack CDK sites had defects in estradiol (E2)-mediated cell cycle progression and significantly affected PELP1-mediated oncogenic functions in vivo. Mechanistic studies showed that PELP1 modulates transcription factor E2F1 transactivation functions, that PELP1 is recruited to pRb/E2F target genes, and that PELP1 facilitates ER signaling cross talk with cell cycle machinery. We conclude that PELP1 is a novel substrate of interphase CDKs and that its phosphorylation is important for the proper function of PELP1 in modulating hormone-driven cell cycle progression and also for optimal E2F transactivation function. Because the expression of both PELP1 and CDKs is deregulated in breast tumors, CDK-PELP1 interactions will have implications in breast cancer progression.
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U2 - 10.1158/0008-5472.CAN-10-0628
DO - 10.1158/0008-5472.CAN-10-0628
M3 - Article
C2 - 20807815
AN - SCOPUS:77956914563
SN - 0008-5472
VL - 70
SP - 7166
EP - 7175
JO - Cancer Research
JF - Cancer Research
IS - 18
ER -