TY - JOUR
T1 - Leukemic transformation by the v-ErbA oncoprotein entails constitutive binding to and repression of an erythroid enhancer in vivo
AU - Ciana, Paolo
AU - Braliou, Georgia G.
AU - Demay, Florence G.
AU - Von Lindern, Marieke
AU - Barettino, Domingo
AU - Beug, Hartmut
AU - Stunnenberg, Hendrik G.
PY - 1998/12/15
Y1 - 1998/12/15
N2 - v-ErbA, a mutated thyroid hormone receptor alpha (TRα), is thought to contribute to avian erythroblastosis virus (AEV)-induced leukemic transformation by constitutively repressing transcription of target genes. However, the binding of v-ErbA or any unliganded nuclear receptor to a chromatin-embedded response element as well as the role of the N-CoR-SMRT-HDAC co-repressor complex in mediating repression remain hypothetical. Here we identify a v-ErbA-response element, VRE, in an intronic DNase I hypersensitive site (HS2) of the chicken erythroid carbonic anhydrase II (CAII) gene. In vivo footprinting shows that v-ErbA is constitutively bound to this HS2-VRE in transformed, undifferentiated erythroblasts along with other transcription factors like GATA-1. Transfection assays show that the repressed HS2 region can be turned into a potent enhancer in v-ErbA-expressing cells by mutation of the VRE. Differentiation of transformed cells alleviates v-ErbA binding concomitant with activation of CAII transcription. Co-expression of a gag-TRα fusion protein in AEV-transformed cells and addition of ligand derepresses CAII transcription. Treatment of transformed cells with the histone deacetylase inhibitor, trichostatin A, derepresses the endogenous, chromatin-embedded CAII gene, while a transfected HS2-enhancer construct remains repressed. Taken together, our data suggest that v-ErbA prevents CAII activation by 'neutralizing' in cis the activity of erythroid transcription factors.
AB - v-ErbA, a mutated thyroid hormone receptor alpha (TRα), is thought to contribute to avian erythroblastosis virus (AEV)-induced leukemic transformation by constitutively repressing transcription of target genes. However, the binding of v-ErbA or any unliganded nuclear receptor to a chromatin-embedded response element as well as the role of the N-CoR-SMRT-HDAC co-repressor complex in mediating repression remain hypothetical. Here we identify a v-ErbA-response element, VRE, in an intronic DNase I hypersensitive site (HS2) of the chicken erythroid carbonic anhydrase II (CAII) gene. In vivo footprinting shows that v-ErbA is constitutively bound to this HS2-VRE in transformed, undifferentiated erythroblasts along with other transcription factors like GATA-1. Transfection assays show that the repressed HS2 region can be turned into a potent enhancer in v-ErbA-expressing cells by mutation of the VRE. Differentiation of transformed cells alleviates v-ErbA binding concomitant with activation of CAII transcription. Co-expression of a gag-TRα fusion protein in AEV-transformed cells and addition of ligand derepresses CAII transcription. Treatment of transformed cells with the histone deacetylase inhibitor, trichostatin A, derepresses the endogenous, chromatin-embedded CAII gene, while a transfected HS2-enhancer construct remains repressed. Taken together, our data suggest that v-ErbA prevents CAII activation by 'neutralizing' in cis the activity of erythroid transcription factors.
KW - Carbonic anhydrase II
KW - Repression
KW - Thyroid hormone
KW - Trichostatin A
KW - v-ErbA
UR - http://www.scopus.com/inward/record.url?scp=0032535206&partnerID=8YFLogxK
U2 - 10.1093/emboj/17.24.7382
DO - 10.1093/emboj/17.24.7382
M3 - Article
C2 - 9857194
AN - SCOPUS:0032535206
SN - 0261-4189
VL - 17
SP - 7382
EP - 7394
JO - EMBO Journal
JF - EMBO Journal
IS - 24
ER -