Regulation of ERK1 gene expression by coactivator proteins.
RARs (retinoic acid receptors) mediate the effect of their ligand RA (retinoic acid) on gene expression. We previously showed that RA inhibited cellular proliferation in part by decreasing expression of the mitogen activated protein kinase ERK1 (extracellular signal regulated kinase 1). However, the mechanism by which RA regulates ERK1 expression is largely uncharacterized. The present study characterizes coactivator-mediated regulation of RA target gene expression by analysing ERK1 promoter activation. CBP (CREB-binding protein) and PCAF (p300/CBP associated factor) are transcriptional coactivators that interact with nuclear hormone receptors such as RARs. CBP and PCAF differentially regulated ERK1 expression in stable clones. CBP clones expressed higher ERK1 protein levels, proliferated faster in culture and were resistant to RA-mediated growth inhibition. PCAF clones expressed lower levels of ERK1 protein and cells grew more slowly than controls. CBP and PCAF regulation of the ERK1 promoter was dependent on two Sp1 (specificity protein 1) sites located between -86 and -115 bp. Immunoprecipitation and yeast two-hybrid analysis revealed that PCAF interacted with Sp1 via CBP. A putative p53 binding site at -360 bp functioned as a major repressor of ERK1 promoter activity even in the absence of exogenous p53 expression. CBP and PCAF occupancy of the proximal ERK1 promoter was dramatically decreased by RA treatment. PCAF mediated inhibition of ERK1 expression was due to decreased stability of the kinase mRNA. We conclude that CBP and PCAF coactivators mediate ERK1 gene expression at both the transcriptional and post-transcriptional level.
Chu
Beanca Y
BY
Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA.
Tran
Kim
K
Ku
Tony K S
TK
Crowe
David L
DL
D050882:CREB-Binding Protein / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015971:Gene Expression Regulation, Enzymologic; D051548:Histone Acetyltransferases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014212:Tretinoin / Q000378:metabolism; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
D050882:CREB-Binding Protein; D018797:Cell Cycle Proteins; D051548:Histone Acetyltransferases; D048052:Mitogen-Activated Protein Kinase 3; D012333:RNA, Messenger; D014157:Transcription Factors; D014212:Tretinoin; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C494363:CREBBP protein, human