p300/cAMP-response-element-binding-protein ('CREB')-binding protein (CBP) modulates co-operation between myocyte enhancer factor 2A (MEF2A) and thyroid hormone receptor-retinoid X receptor.
Thyroid hormone receptors (TRs) and members of the myocyte enhancer factor 2 (MEF2) family are involved in the regulation of muscle-specific gene expression during myogenesis. Physical interaction between these two factors is required to synergistically activate gene transcription. p300/cAMP-response-element-binding-protein ('CREB')-binding protein (CBP) interacting with transcription factors is able to increase their activity on target gene promoters. We investigated the role of p300 in regulating the TR-MEF2A complex. To this end, we mapped the regions of these proteins involved in physical interactions and we evaluated the expression of a chloramphenicol acetyltransferase (CAT) reporter gene in U2OS cells under control of the alpha-myosin heavy chain promoter containing the thyroid hormone response element (TRE). Our results suggested a role of p300/CBP in mediating the transactivation effects of the TR-retenoid X receptor (RxR)-MEF2A complex. Our findings showed that the same C-terminal portion of p300 binds the N-terminal domains of both TR and MEF2A, and our in vivo studies demonstrated that TR, MEF2A and p300 form a ternary complex. Moreover, by the use of CAT assays, we demonstrated that adenovirus E1A inhibits activation of transcription by TR-RxR-MEF2A-p300 but not by TR-RxR-MEF2A. Our data suggested that p300 can bind and modulate the activity of TR-RxR-MEF2A at TRE. In addition, it is speculated that p300 might modulate the activity of the TR-RxR-MEF2A complex by recruiting a hypothetical endogenous inhibitor which may act like adenovirus E1A.
De Luca
Antonio
A
Department of Experimental Medicine and Pathology, IRCCS, Neuromed, Rome, Italy. antonio.deluca@unina2.it
Severino
Anna
A
De Paolis
Paola
P
Cottone
Giuliano
G
De Luca
Luca
L
De Falco
Maria
M
Porcellini
Antonio
A
Volpe
Massimo
M
Condorelli
Gianluigi
G
D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D047488:Retinoid X Receptors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D002843:Chromatin; D004268:DNA-Binding Proteins; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; C578035:MEF2A protein, human; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D047488:Retinoid X Receptors; D015534:Trans-Activators; D014157:Transcription Factors; D015500:Chloramphenicol O-Acetyltransferase