Oncogenic STRAP functions as a novel negative regulator of E-cadherin and p21(Cip1) by modulating the transcription factor Sp1.
We have previously reported the identification of a novel WD-domain protein, STRAP that plays a role in maintenance of mesenchymal morphology by regulating E-cadherin and that enhances tumorigenicity partly by downregulating CDK inhibitor p21(Cip1). However, the functional mechanism of regulation of E-cadherin and p21(Cip1) by STRAP is unknown. Here, we have employed STRAP knock out and knockdown cell models (mouse embryonic fibroblast, human cancer cell lines) to show how STRAP downregulates E-cadherin and p21(Cip1) by abrogating the binding of Sp1 to its consensus binding sites. Moreover, ChIP assays suggest that STRAP recruits HDAC1 to Sp1 binding sites in p21(Cip1) promoter. Interestingly, loss of STRAP can stabilize Sp1 by repressing its ubiquitination in G1 phase, resulting in an enhanced expression of p21(Cip1) by >4.5-fold and cell cycle arrest. Using Bioinformatics and Microarray analyses, we have observed that 87% mouse genes downregulated by STRAP have conserved Sp1 binding sites. In NSCLC, the expression levels of STRAP inversely correlated with that of Sp1 (60%). These results suggest a novel mechanism of regulation of E-cadherin and p21(Cip1) by STRAP by modulating Sp1-dependent transcription, and higher expression of STRAP in lung cancer may contribute to downregulation of E-cadherin and p21(Cip1) and to tumor progression.
['Jin|Lin|L|', 'Datta|Pran K|PK|']
D000818:Animals D001665:Binding Sites D015820:Cadherins D002352:Carrier Proteins D059447:Cell Cycle Checkpoints D002460:Cell Line D050759:Cyclin-Dependent Kinase Inhibitor p21 D015536:Down-Regulation D016193:G1 Phase D057809:HEK293 Cells D006367:HeLa Cells D056284:Histone Deacetylase 1 D006801:Humans D051379:Mice D011401:Promoter Regions, Genetic D011485:Protein Binding D034622:RNA Interference D012333:RNA, Messenger D016329:Sp1 Transcription Factor D015533:Transcriptional Activation D054875:Ubiquitination
STRAP transcription factor Sp1 ubiquitination cell cycle CDK2, cyclin-dependent kinase 2 CDK4, cyclin-dependent kinase 4 HDAC1, histone deacetylase 1 HDAC2, histone deacetylase 2 HDAC3, histone deacetylase 3 HNF4, hepatocyte nuclear factor 4 MEF, mouse embryonic fibroblast NF-YA, nuclear transcription factor Y subunit alpha PARP, poly (ADP-ribose) polymerase RNase, A ribonuclease A RhoA, Ras homolog gene family, member A STRAP, serine threonine kinase receptor-associated protein SWI/SNF, SWItch/Sucrose nonfermentable Sp/KLF, specificity protein/Krüppel-like factor Sp1, specificity protein 1 TSA, trichostatin A TSS, transcription start site TβR I, II, TGF-β receptor I, II p300/CBP, p300/ CREB-binding protein