NeP1

The thyroid hormone (T3) blocks proliferation and induces differentiation of neuroblastoma N2a-␤ cells that express the thyroid hormone receptor (TR) ␤1 isoform. c-Myc is required for cell cycle progression, and this study shows that T3-induced neuronal differentiation is preceded by a rapid decrease of c-myc gene expression. A negative T3 responsive element (TRE), arranged as an inverted palindrome spaced by three nucleotides, has been identified within the first exon between nucleotides ؉237 and ؉268. The TRE is adjacent to the binding site for the transcriptional repressor CCCTC binding factor and maps precisely within the region of RNA polymerase II pausing and release, suggesting a direct implication of TR on premature termination of transcription. Furthermore, the TRE confers repression by T3 to an heterologous promoter only when inserted downstream of the transcription initiation site. Binding of CCCTC binding factor and TR to their cognate sites in the region of transcriptional attenuation, as well as direct interactions between both factors, could facilitate the formation of a repressor complex and the inhibition of c-myc gene expression. These studies provide insight into mechanisms by which TR mediate transcriptional repression and contribute to the understanding of the important effects of thyroid hormones on growth and differentiation of neuronal cells.

Section: Discussionmentioning

confidence: 99%

An Element in the Region Responsible for Premature Termination of Transcription Mediates Repression of c-myc Gene Expression by Thyroid Hormone in Neuroblastoma Cells

Pérez-Juste¹,

García‐Silva

Aranda

2000

“…In the human and mouse c-myc genes CTCF binds to divergent recognition sequences coinciding with RNA polymerase pausing sites in the transcribed region of the genes (35). In addition, a protein designated NeP1 was identified that binds to the chicken lysozyme silencer 2.4 kilobase pairs upstream from the transcriptional start site and synergistically represses transcription in conjunction with v-ERBA, the thyroid hormone receptor, or the retinoic acid receptor (31,43). NeP1 has since been found to be identical to CTCF (32).…”

Section: Discussionmentioning

confidence: 99%

The Zinc Finger Protein CTCF Binds to the APBβ Domain of the Amyloid β-Protein Precursor Promoter

Vostrov

Quitschke

1997

174

159

The promoter of the amyloid ␤-protein precursor (APP) gene directs high levels of cell type-specific transcription with 94 base pairs 5 to the main transcriptional start site. An essential activator domain in this proximal APP promoter is a nuclear factor binding site designated as APB␤. The recognition domain for the APB␤ binding factor is located between position ؊93 and ؊82 relative to the main transcriptional start site.The nuclear factor that binds to the APB␤ site was partially purified by multiple steps of ion exchange and hydroxyapatite chromatography. Based on UV crosslinking results, a protein with an apparent molecular mass of 140 kDa was selected as the putative APB␤ binding protein. After the final purification step consisting of preparative SDS-polyacrylamide gel electrophoresis, partial peptide sequences were obtained that completely matched the transcriptional factor CTCF. This protein is a known regulator of c-myc and lysozyme gene expression, and it binds to a variety of diverse DNA sequences.The binding of CTCF to the APB␤ domain was further established by competition with CTCF binding oligonucleotides in mobility shift electrophoresis. The identity was also confirmed by the observation that the APB␤ binding factor is recognized by antibodies against Cand N-terminal sequences of CTCF. In addition, oligonucleotide competition during in vitro transcription affirmed that CTCF acts as a transcriptional activator in the APP gene promoter.

“…Similarly, protein p 1 would be only recognized by the C-terminal antibody. Finally, neither antibody would recognize the proteins p 10 and p 2 that produce binding complexes b 10 and b 2 .…”

Section: Treatment Of Nuclear Extract With Serum Changes the Mobilitymentioning

confidence: 99%

“…This protein was first identified as a factor that binds to the chicken c-myc promoter (7) and to the silencer element of the chicken lysozyme gene (8,9). A functional role for CTCF in both positive and negative transcriptional regulation has been documented (5,6,10,11).…”

mentioning

confidence: 99%

Plasma Hyaluronan-binding Protein Is a Serine Protease

Vostrov

Quitschke

2000

CTCF is an essential factor for optimal transcription from the amyloid ␤-protein precursor promoter. A proteolytic activity detected in bovine, rabbit, horse, and human serum cleaves CTCF at three major sites, resulting in a modified mobility shift pattern of the fragments that retain DNA binding ability. The protease was purified to electrophoretic homogeneity, partially sequenced, and identified as the plasma hyaluronan-binding protein.