The molecular mechanisms involved in the regulation of gene expression by transforming growth factor-13 (TGF-13) have been analyzed. We show that TGF-~ specifically induces the activity of the proline-rich trans-activation domain of CTF-1, a member of the CTF/NF-I family of transcription factors. A TGF-13-responsive domain (TRD) in the proline-rich transcriptional activation sequence of CTF-I was shown to mediate TGF-13 induction in NIH-3T3 cells. Mutagenesis studies indicated that this domain is not the primary target of regulatory phosphorylations, suggesting that the growth factor may regulate a CTF-l-interacting protein. A two-hybrid screening assay identified a nucleosome component, histone H3, as a specific CTF-l-interacting protein in yeast. Furthermore, the CTF-1 trans-activation domain was shown to interact with histone H3 in both transiently and stably transfected mammalian cells. This interaction requires the TRD, and it appears to be upregulated by TGF-f~ in vivo. Moreover, point mutations in the TRD that inhibit TGF-f~ induction also reduce interaction with histone H3. In vitro, the trans-activation domain of CTF-1 specifically contacts histone H3 and oligomers of histones H3 and H4, and full-length CTF-1 was shown to alter the interaction of reconstituted nucleosomal cores with DNA. Thus, the growth factor-regulated trans-activation domain of CTF-1 can interact with chromatin components through histone H3. These findings suggest that such interactions may regulate chromatin dynamics in response to growth factor signaling.
Transforming growth factor  (TGF-) and platelet-derived growth factor A (PDGF〈) play a central role in tissue morphogenesis and repair, but their interplay remain poorly understood. The nuclear factor I C (NFI-C) transcription factor has been implicated in TGF- signaling, extracellular matrix deposition, and skin appendage pathologies, but a potential role in skin morphogenesis or healing had not been assessed. To evaluate this possibility, we performed a global gene expression analysis in NFI-C ؊/؊ and wild-type embryonic primary murine fibroblasts. This indicated that NFI-C acts mostly to repress gene expression in response to TGF-1. Misregulated genes were prominently overrepresented by regulators of connective tissue inflammation and repair. In vivo skin healing revealed a faster inflammatory stage and wound closure in NFI-C ؊/؊ mice. Expression of PDGFA and PDGF-receptor alpha were increased in wounds of NFI-C ؊/؊ mice, explaining the early recruitment of macrophages and fibroblasts. Differentiation of fibroblasts to contractile myofibroblasts was also elevated, providing a rationale for faster wound closure. Taken together with the role of TGF- in myofibroblast differentiation, our results imply a central role of NFI-C in the interplay of the two signaling pathways and in regulation of the progression of tissue regeneration.
Transcription initiation at eukaryotic protein-coding gene promoters is regulated by a complex interplay of site-specific DNA-binding proteins acting synergistically or antagonistically. Here, we have analyzed the mechanisms of synergistic transcriptional activation between members of the CCAAT-binding transcription factor/nuclear factor I (CTF/NF-I) family and the estrogen receptor. By using cotransfection experiments with HeLa cells, we show that the proline-rich transcriptional activation domain of CTF-1, when fused to the GAL4 DNA-binding domain, synergizes with each of the two estrogen receptor-activating regions. Cooperative DNA binding between the GAL4-CTF-1 fusion and the estrogen receptor does not occur in vitro, and in vivo competition experiments demonstrate that both activators can be specifically inhibited by the overexpression of a proline-rich competitor, indicating that a common limiting factor is mediating their transcriptional activation functions. Furthermore, the two activators functioning synergistically are much more resistant to competition than either factor alone, suggesting that synergism between CTF-1 and the estrogen receptor is the result of a stronger tethering of the limiting target factor(s) to the two promoter-bound activators.Transcription of eukaryotic protein-coding genes is controlled by the combinatorial arrangement of regulatory proteins that bind specific DNA elements located either upstream or downstream of a core promoter. Structural and functional analyses have revealed that sequence-specific activators are modular in structure. They most often contain at least two generally independent functional regions: a DNA-binding domain and a transcriptional activation domain, in addition to oligomerization and nuclear localization determinants. Four main distinct types of activation motifs, tentatively grouped according to their different amino acid compositions, have been identified thus far: the acidic negatively charged domains, the glutamine-rich domains, the proline-rich domains (34, 37), and the metal-binding cysteine-containing activating domain of the adenovirus Ela protein (29).Activation domains are thought to function by interacting directly or indirectly with general components of the transcription initiation machinery (26,38). This hypothesis is supported by the observation that an activator present at an artificially high intracellular concentration can inhibit its own transcriptional activity as well as that of other activators; this inhibition was previously called squelching or transcriptional interference (12,29,33,46,48). Squelching is thought to occur by the titration of a limiting soluble cellular component of the transcriptional machinery (the target) through its interaction with the activation domain of the overexpressed activator. Thus, squelching may result in the sequestration of the target, which can no longer interact with promoter-bound activators to mediate their transcriptional activation functions (37,38 synergistically with other activators recog...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.