DNA Recognition by Normal and Oncogenic Thyroid Hormone Receptors

Judelson, Catherine; Privalsky, Martin L.

doi:10.1074/jbc.271.18.10800

Cited by 40 publications

(13 citation statements)

References 45 publications

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“…Both class I (62,63) and class II NHRs (50) are known to tolerate variation in primary DNA sequence and half-site spacing of their target sites. The naturally occurring TREs in the TR␤A gene locus conform to findings from several in vitro studies (43,50,64); for example an "A-G" transition at position 1 in the AGGTCA half-site was shown to enhance TR/RXR binding by ϳ40%, whereas a "C-T" transition in position 5 reduced it to ϳ60% of wild type (50). The resulting half-site, GGGTTA, is found in the TR␤A enhancer and efficiently binds TR/RXR in vivo (Fig.…”

Section: Discussionmentioning

confidence: 93%

“…Consistent with their divergence from a 4-bp half-site spacing, elements 2 and 3 bound TR/RXR with lower affinity than element 4 (compare lanes 8 -11 with lanes 6 and 7) or a well defined TRE from the human genome (lanes 4 and 5). A "TRE" with point mutations in all DNA residues crucial for binding (50) (lanes 12 and 13) or a DNA segment of equal length but random sequence (lanes 14 and 15) both failed to compete for TR/RXR binding (compare with lane 1). We obtained identical results in experiments using all these TREs in labeled form rather than as competitors (data not shown).…”

Section: The Tr␤a Promoter Contains Multiple In Vivo Tr-bindingmentioning

confidence: 99%

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An Array of Positioned Nucleosomes Potentiates Thyroid Hormone Receptor Action in Vivo

Urnov

Wolffe

2001

Journal of Biological Chemistry

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The assembly of the genome into chromatin imposes a poorly understood set of rules and constraints on action by regulatory factors. We investigated the role played by chromatin infrastructure in enabling an acute response of the Xenopus TR␤A gene to thyroid hormone receptor (TR), an extensively studied member of the nuclear hormone receptor superfamily. We found that in addition to the known TR response element (TRE) in the promoter, full range regulation required an upstream enhancer that contained multiple nonconsensus TREs and augmented ligand action at high receptor levels. An array of translationally positioned nucleosomes formed over the TR␤A locus in vivo; unliganded TR engaged this array in linker DNA between two nucleosomes and via TREs on the surface of histone octamers. Remarkably, assembly of enhancer DNA into mature chromatin potentiated binding by TR to its target response elements and enabled a greater range of regulation by TR than was observed on immature chromatin templates. Because assembly of enhancer DNA into chromatin increased TR binding to the nonconsensus TREs, we hypothesize that chromatin disruption targeted by liganded TR to the enhancer may lead to receptor release from the template and to an attenuation of response to hormone.The study of transcriptional regulation makes extensive use of artificial reporter constructs that contain several binding sites for a particular protein and are introduced into cells by transfection. This useful approach has two limitations. (i) Bona fide targets of eukaryotic transcription factors are assembled into chromatin, whereas nonreplicating episomes are not (1).(ii) The primary sequence of eukaryotic promoters is seldom a reiteration of binding sites for one protein. With only a few exceptions (2, 3), we are far from understanding how the regulatory behavior of a eukaryotic promoter emerges from the union of nonhistone protein-binding sites that it contains. In general, naturally occurring promoters studied in their native chromosomal context, e.g. the mouse mammary tumor virus long terminal repeat (MMTV LTR) 1 (4 -6), the Drosophila hsp26 gene (7-9), and the human pS2 (10, 11) and cathepsin D (12) promoters, offer a far more intricate picture of transcriptional regulation than assays with synthetic reporter constructs placed on nonreplicating episomes (13).The Xenopus oocyte offers an attractive experimental system for studies of transcription; evolutionarily molded to contain sufficient histone protein and chromatin assembly machinery for several thousand somatic cells, it efficiently assembles microinjected DNA into physiologically spaced chromatin (14), which offers an excellent opportunity to investigate functional interactions between various regulatory factors and chromatin templates in vivo (15-20). The power of this model system is illustrated by data from our laboratory on action by the thyroid hormone receptor (TR); this extensively studied member of the nuclear hormone receptor (NHR) superfamily is exquisitely sensitive to nanomolar quant...

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Section: Discussionmentioning

confidence: 93%

Section: The Tr␤a Promoter Contains Multiple In Vivo Tr-bindingmentioning

confidence: 99%

An Array of Positioned Nucleosomes Potentiates Thyroid Hormone Receptor Action in Vivo

Urnov

Wolffe

2001

Journal of Biological Chemistry

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“…Intriguingly, a dominant-negative mutant of TRa1 implicated in avian leukemogenesis, v-Erb A, has also sustained substitutions in its DNA recognition domain that alter its half-site specificity and that contribute to its leukemogenicity Sande et al, 1993;Judelson and Privalsky, 1996). We suggest that analogous alterations in the DNA recognition domain in the TRa1 HCC mutants result in alterations in their target gene repertoire that contribute to their oncogenic properties and that these changes in target gene specificity may help to distinguish the neoplastic TR alleles from the 'simple' dominantnegative mutations associated with inherited RTH Syndrome.…”

Section: Discussionmentioning

confidence: 99%

Thyroid hormone receptors mutated in liver cancer function as distorted antimorphs

Chan

Privalsky

2006

Oncogene

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Aberrant thyroid hormone receptors (TRs) are found in over 70% of the human hepatocellular carcinomas (HCCs) analysed. To better understand the role(s) of these TR mutants in this neoplasia, we analysed a panel of HCC mutant receptors for their molecular properties. Virtually all HCC-associated TR mutants tested retained the ability to repress target genes in the absence of T3, yet were impaired in T3-driven gene activation and functioned as dominant-negative inhibitors of wild-type TR activity. Intriguingly, the HCC TRa1 mutants exerted dominantnegative interference at all T3 concentrations tested, whereas the HCC TRb1 mutants were dominant-negatives only at low and intermediate T3 concentrations, reverting to transcriptional activators at higher hormone levels. The relative affinity for the SMRT versus N-CoR corepressors was detectably altered for several of the HCC mutant TRs, suggesting changes in corepressor preference and recruitment compared to wild type. Several of the TRa HCC mutations also altered the DNA recognition properties of the encoded receptors, indicating that these HCC TR mutants may regulate a distinct set of target genes from those regulated by wild-type TRs. Finally, whereas wild-type TRs interfere with c-Jun/AP-1 function in a T3-dependent fashion and suppress anchorageindependent growth when ectopically expressed in HepG2 cells, at least certain of the HCC mutants did not exert these inhibitory properties. These alterations in transcriptional regulation and DNA recognition appear likely to contribute to oncogenesis by reprogramming the differentiation and proliferative properties of the hepatocytes in which the mutant TRs are expressed.

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“…1A). This discrepancy may reflect the weaker interaction of cT 3 R␣(21-408, 7/8) with TFIIB, which could result in a number of transcriptionally active cT 3 24 and Tyr 44 of cT 3 R␣) have been shown, in conjunction with amino acid changes in the zinc finger domain, to contribute to a restricted half-site DNA binding specificity (45,47,52). RXR␣ and RXR␥, but not RXR␤, have been suggested to activate transcription by forming tetrameric complexes on DNA elements consisting of four reiterated weak half-sites (53).…”

Section: Krkrkmentioning

confidence: 99%

A Novel Multifunctional Motif in the Amino-terminal A/B Domain of T3Rα Modulates DNA Binding and Receptor Dimerization

Hadzic¹,

Habeos²,

Raaka³

et al. 1998

Journal of Biological Chemistry

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We reported previously that deletion of the 50-amino acid NH 2 -terminal A/B domain of the chicken (c) or rat thyroid hormone (T 3 ) receptor-␣ (T 3 R␣) decreased the T 3 -dependent stimulation of genes regulated by native thyroid hormone response elements (TREs). This requirement of the NH 2 -terminal A/B domain for transcriptional activation was mapped to amino acids 21-30 of cT 3 R␣. Expression of transcription factor IIB (TFIIB) in cells was shown to enhance T 3 -dependent transcriptional activation by cT 3 R␣, and this enhancement by TFIIB was dependent on the same 10-amino acid sequence. In vitro binding studies indicated that cT 3 R␣ interacts efficiently with TFIIB, and this interaction requires amino acids 23 KRKRK 27 in the A/B domain. In this study we document the functional importance of these five basic residues in transcriptional activation by cT 3 R␣, further supporting the biological significance of these residues and their interaction with TFIIB. Interestingly, we also find that the same amino acids also affect DNA binding and dimerization of cT 3 R␣. Gel mobility shift assays reveal that a cT 3 R␣ mutant that has all five basic amino acids changed from 23 KRKRK 27 to 23 TITIT 27 binds to a palindromic TRE predominantly as a homodimer, whereas cT 3 R␣ with the wild-type 23 KRKRK 27 sequence binds predominantly as a monomer. This results from both a marked decrease in the ability of the cT 3 R␣ mutant to bind as a monomer and from an enhanced ability to dimerize as reflected by an increase in DNA-bound T 3 R-retinoic X receptor heterodimers. These effects of 23 KRKRK 27 on DNA binding, dimerization, transcriptional activation, and the association of T 3 R␣ with TFIIB support the notion that this basic amino acid motif may influence the overall structure and function of T 3 R␣ and, thus, play a role in determining the distinct context-dependent transactivation potentials of the individual T 3 R isoforms.Steroid, retinoid, and thyroid hormone nuclear receptors are ligand-dependent transcription factors that couple extracellular signals directly to transcriptional responses. These receptors activate or repress transcription of target genes by binding to specific DNA sequences referred to as hormone response elements (HREs) 1 (1). The nuclear receptor superfamily can be divided into the steroid hormone receptor family and the thyroid hormone/retinoid receptor family (1, 2), which includes receptors that mediate the effects of thyroid hormone [L-triiodothyronine (T 3 ) (the T 3 Rs), all-trans-retinoic acid (the RARs), 9-cis-retinoic acid (the RARs and RXRs), and 1,25-dihydroxyvitamin D 3 as well as several orphan receptors (e.g. COUP-TF, c-erbA␣2) whose ligand(s), if any, are unknown (3-5).The T 3 Rs are encoded by two distinct but closely related genes (␣ and ␤) which, in humans (h), map to chromosomes 17 and 3, respectively (6). Each gene expresses several alternatively spliced isoforms. The T 3 R␣ gene in the rat (r) and man expresses the T 3 -binding isoform T 3 R␣1 along with c-erbA␣2, which does...

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DNA Recognition by Normal and Oncogenic Thyroid Hormone Receptors

Cited by 40 publications

References 45 publications

An Array of Positioned Nucleosomes Potentiates Thyroid Hormone Receptor Action in Vivo

An Array of Positioned Nucleosomes Potentiates Thyroid Hormone Receptor Action in Vivo

Thyroid hormone receptors mutated in liver cancer function as distorted antimorphs

A Novel Multifunctional Motif in the Amino-terminal A/B Domain of T3Rα Modulates DNA Binding and Receptor Dimerization

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