Characterization of the DNA-binding and dominant negative activity of v-erbA homodimers.
The oncoprotein v-erbA is a mutated form of thyroid hormone receptor alpha1 that is virtually incapable of binding T3. V-erbA is a dominant repressor of transcription induced by thyroid hormone receptors and retinoic acid receptors; however, the genetic targets of v-erbA that lead to oncogenesis are not known. Although v-erbA can bind as monomers and dimers to DNA containing the consensus sequence AGGTCA arranged as direct, inverted, or everted repeats, it is not known which sequence represents the optimal v-erbA-binding site. Determination of the DNA recognition properties of v-erbA would allow a better understanding of the repressor activity of this oncoprotein. The current studies, by using a random DNA selection strategy, have determined that the imperfect everted repeat 5'-TGACC(T/C)NT(A/G)AGGTCAC is the optimal v-erbA homodimer-binding site, where N represents any di- or trinucleotide. Functional studies show that everted repeats containing this sequence are substantially more potent v-erbA response elements than direct or inverted repeats, even though many classic T3 response elements are direct repeats. Thus, v-erbA represses only a subset of T3 response elements. In a similar fashion, v-erbA was found to repress a subset of vitamin D response elements. Of general interest, the data indicate that the two molecules of a transcription factor homodimer do not necessarily have identical DNA-binding specificities.
Subauste
J S
JS
Division of Endocrinology and Metabolism, University of Mississippi Medical Center, Jackson 39216, USA.
Koenig
R J
RJ
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D016384:Consensus Sequence; D004247:DNA / Q000378:metabolism*; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D019281:Dimerization; D006147:Guanine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D018774:Oncogene Proteins v-erbA / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014498:Uracil / Q000378:metabolism; D014807:Vitamin D / Q000378:metabolism
D018774:Oncogene Proteins v-erbA; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D014807:Vitamin D; D014498:Uracil; D006147:Guanine; D004247:DNA