The mammalian protein DEK has been implicated in multiple cellular processes, including transcriptional regulation, mRNA processing, and chromatin remodeling, and is associated with a number of clinical autoimmune and neoplastic conditions. The connection between DEK and cancer exists at multiple levels: (a) the t(6;9) chromosomal translocation that characterizes a subtype of acute myelogenous leukemia cases results in the formation of a DEK-CAN fusion oncoprotein; (b) a fragment of dek cDNA is capable of partially reversing the radiation-sensitive phenotype of fibroblasts cultured from ataxia-telangiectasia patients; and (c) increased levels of dek mRNA have been found to be associated with hepatocellular carcinoma, glioblastoma, and melanoma. Despite the growing list of cancer subtypes with a connection to DEK, the factors that mediate its expression have yet to be characterized. Here we undertake the analysis of DEK regulation by mapping the discrete elements within the proximal promoter that are responsible for constitutive transcription of dek in transformed cells. We find that functional elements include an inverted CCAAT box and a YY1 consensus binding site, and the introduction of point mutations into these sites markedly diminishes transcriptional activity. In addition, we identify the transcriptional activator NF-Y as a member of the CCAAT-binding complex, and verify binding of the transcription factor YY1 at its consensus site in the dek promoter. The discovery of NF-Y and YY1 as regulatory determinants of DEK expression is consistent with the well-documented roles of these two factors in cellular proliferation and transformation.
Cells in the caudal mesencephalon and rostral metencephalon become organized by signals emanating from the isthmus organizer (IsO). The IsO is associated with the isthmus, a morphological constriction of the neural tube which eventually defines the mesencephalic/ metencephalic boundary (MMB). Here we report that the transcription factor Lmx1b is expressed and functions in a distinct region of the IsO. Lmx1b expression is maintained by the glycoprotein Fgf8, a signal capable of mediating IsO signaling. Lmx1b, in turn, maintains the expression of the secreted factor Wnt1. Our conclusions are substantiated by the following: (i) Lmx1b mRNA becomes localized to the isthmus immediately after Fgf8 initiation, (ii) Wnt1 expression is localized to the Lmx1b expression domain, but with slightly later kinetics, (iii) Fgf8-soaked beads generate similar domains of expression for Lmx1b and Wnt1 and (iv) retroviral-mediated expression of Lmx1b (Lmx1b/RCAS) maintains Wnt1 expression in the mesencephalon. Ectopic Lmx1b is insufficient to alter the expression of a number of other genes expressed at the IsO, suggesting that it does not generate a new signaling center. Instead, if we allow Lmx1b/RCAS-infected brains to develop longer, we detect changes in mesencephalic morphology. Since both ectopic and endogenous Lmx1b expression occurs in regions of the isthmus undergoing morphological changes, it could normally play a role in this process. Furthermore, a similar phenotype is not observed in Wnt1/RCAS-infected brains, demonstrating that ectopic Wnt1 is insufficient to mediate the effect of ectopic Lmx1b in our assay. Since Wnt1 function has been linked to the proper segregation of mesencephalic and metencephalic cells, we suggest that Lmx1b and Wnt1 normally function in concert to affect IsO morphogenesis.
Several cis-acting elements regulate the expression of germline transcripts of heavy chain constant region genes and their subsequent switch recombination. To study such elements in the murine gamma1 gene, we have utilized a transgenic approach. In this study we focused on a DNase I hypersensitive site (termed 'Site II') that lies about 2 kb 3' of the gamma1 promoter region and I exon, just 5' to the gamma1 switch region. We have reported that gamma1 transgenes with Site II display the characteristics of a locus control region (LCR) in that they are insertion site independent and copy number dependent. For the present study we prepared six lines of transgenic mice that have the promoter region and I exon, but lack Site II. Expression of RNA from gamma1 transgenes that lack Site II is not correlated with transgene copy number; expression is insertion site dependent. This result indicates that DNase hypersensitive Site II is an important part of the LCR-like elements in the murine gamma1 gene. RNA expression from the gamma1 transgenes that lack Site II is inducible by IL-4 and by CD40 ligation. However, the induction of transgenic RNA expression by CD40 ligation is greater than expected, suggesting that elements within Site II participate in negative regulation of the amount of germline transcripts after CD40 ligation.
No abstract
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.