Untitled

Fedorov, Lev M.; Tyrsin, Oleg Yu.; Krenn, Veit; Chernigovskaya, E. V.; Rapp, Ulf R.

doi:10.1023/a:1016632110931

Cited by 22 publications

(4 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Noteworthy, many conditional transgenic mice lines have been established based on a tetR-containing transactivator, the functionality of which eliminates the possibility that the presence of a tetR domain be in itself responsible for triggering CpG methylation (31)(32)(33)(34). Our results thus warrant experiments aimed at determining whether a lack of KRAB-mediated DNA methylation contributes to the early embryonic lethality of KAP1 knockouts.…”

Section: Discussionmentioning

confidence: 76%

The Krüppel-associated Box Repressor Domain Can Trigger de Novo Promoter Methylation during Mouse Early Embryogenesis

Wiznerowicz

Jakobsson

Szulc

et al. 2007

Journal of Biological Chemistry

107

105

View full text Add to dashboard Cite

The Krüppel-associated box (KRAB) domain is a transcriptional repression module responsible for the DNA binding-dependent gene silencing activity of hundreds of vertebrate zinc finger proteins. We previously exploited KRAB-mediated repression within the context of a tet repressor-KRAB fusion protein and of lentiviral vectors to create a method of external gene control. We demonstrated that with this system transcriptional silencing was fully reversible in cell culture as well as in vivo. Here we reveal that, in sharp contrast, KRAB-mediated repression results in irreversible gene silencing through promoter DNA methylation if it acts during the first few days of mouse development.The human genome encodes several hundreds of KRAB 4 -containing ZFPs, a vertebrate-specific family of DNA-binding factors that likely plays major roles in gene regulatory networks important for ontogenesis, differentiation, and cell growth (1-4). When tethered to DNA via their zinc finger motifs, KRAB-ZFPs recruit the KAP1 (KRAB-associated protein 1) corepressor (also known as TIF1␤, transcription intermediary factor 1␤; KRIP1, KRAB-interacting protein 1; or TRIM28, tripartite motif protein 28) via their KRAB domain. KAP1 is characterized by the presence of a RING finger, B-boxes, a coiledcoil region, a PHD finger, and a bromodomain (5-7). The first three of these motifs define the so-called RBCC or TRIM domain, which is both necessary and sufficient for homo-oligomerization and direct binding to KRAB. Upon recruitment to DNA loci, KAP1 functions as a scaffold for the formation of a multimolecular complex comprising HP1 (heterochromatin protein 1), histone deacetylases, and histone methyltransferases, which induces transcriptional repression through the formation of heterochromatin (8, 9). The primordial importance of this process from the earliest stage of mammalian development is supported by the embryonic lethality of the mouse KAP1 knock-out, which results in failure to gastrulate and death at day E5.5 (10). Considering the obvious importance of KRAB-mediated gene control, it is quite remarkable that only very few gene targets of the KRAB-containing ZFPs have so far been identified (11).We described previously a conditional gene regulation system based on the use of the tetracycline-controllable trans-repressor tTRKRAB, a chimeric protein built by fusing KRAB with the DNA binding domain of the Escherichia coli tetracycline repressor (tetR). Upon binding tetracycline operator (tetO) sequences, tTRKRAB induces transcriptional repression, which can silence RNA polymerase I, II, and III promoters situated within a radius of a few kilobases, thus allowing for doxycycline-regulated gene expression and knockdown (12-15) (Fig. 1A). Using lentiviral vectors as vehicles for this system, we demonstrated that KRAB-induced silencing is fully reversible in vitro and in vivo even after prolonged periods of repression in diverse contexts such as in a variety of established human and murine cell lines, in primary cells, including mouse ES cells, and ...

show abstract

Section: Discussionmentioning

confidence: 76%

The Krüppel-associated Box Repressor Domain Can Trigger de Novo Promoter Methylation during Mouse Early Embryogenesis

Wiznerowicz

Jakobsson

Szulc

et al. 2007

Journal of Biological Chemistry

107

105

View full text Add to dashboard Cite

show abstract

“…To induce Tat production during the pre- and early postnatal period, pregnant dams were fed chow containing doxycycline (Harlan, Indianapolis, IN; 6 mg/g) from gestational day 15–16 until postnatal day 7. Doxycycline, a water-soluble tetracycline derivative, crosses the placenta and is secreted in breast milk, and reliably induces transgene expression in embryos and neonates via the tet -on system (Fedorov et al 2001; Perl et al 2002a; Perl et al 2002b; Shin et al 1999). All dams received the same chow, to control for effects of doxycycline unrelated to activation of the tat transgene.…”

Section: Methodsmentioning

confidence: 99%

HIV‐1 alters neural and glial progenitor cell dynamics in the central nervous system: Coordinated response to opiates during maturation

Hahn

Podhaizer

Hauser

et al. 2012

Glia

View full text Add to dashboard Cite

HIV-associated neurocognitive disorders (HAND) are common sequelae of HIV infection, even when viral titers are well controlled by anti-retroviral therapy. Evidence in patients and animal models suggests that neurologic deficits are increased during chronic opiate exposure. We have hypothesized that CNS progenitor cells in both adult and developing CNS are affected by HIV infection, and that opiates exacerbate these effects. To examine this question, neural progenitors were exposed to HIV-1 Tat1-86 in the developing brain of inducible transgenic mice and in vitro. We examined whether Tat affected the proliferation or balance of progenitor populations expressing nestin, Sox2, and Olig2. Disease relevance was further tested by exposing human-derived progenitors to supernatant from HIV-1 infected monocytes. Studies concentrated on striatum, a region preferentially targeted by HIV and opiates. Results were similar among experimental paradigms. Tat or HIV exposure reduced the proliferation of undifferentiated (Sox2+) progenitors and oligodendroglial (Olig2+) progenitors. Co-exposure to morphine exacerbated the effects of Tat or HIV-1SF162 supernatant, but partially reversed HIV-1IIIB supernatant effects. Populations of Sox2+ and Olig2+ cells were also reduced by Tat exposure, although progenitor survival was unaffected. In rare instances, p24 immunolabeling was detected in viable human progenitors by confocal imaging. The vulnerability of progenitors is likely to distort the dynamic balance among neuron/glial populations as the brain matures, perhaps contributing to reports that neurologic disease is especially prevalent in pediatric HIV patients. Pediatric disease is atypical in developed regions, but remains a serious concern in resource-limited areas where infection occurs commonly at birth and through breast-feeding.

show abstract

“…Both transgenics developed multifocal lung adenomas associated with high levels of phosphorylated ERK and high rates of cell proliferation that could be reduced by treatment with the MEK inhibitor CI-1040 [14]. Development of the tumours was also suppressed by bcl-2 deficiency [15] or by bag1 (Bcl-2-associated athanogene 1) haploinsufficiency [16], suggesting that suppression of apoptosis co-operates in lung tumour induction. A similar approach was used to drive V600E BRaf expression from the bovine thyroglobulin promoter that directs expression to thyroid follicular cells [17].…”

Section: Mouse Models For Raf-induced Cancersmentioning

confidence: 99%

Mouse models for BRAF-induced cancers

Pritchard

Carragher

Aldridge

et al. 2007

Biochemical Society Transactions

View full text Add to dashboard Cite

Oncogenic mutations in the BRAF gene are detected in approximately 7% of human cancer samples with a particularly high frequency of mutation in malignant melanomas. Over 40 different missense BRAF mutations have been found, but the vast majority (>90%) represent a single nucleotide change resulting in a valine-->glutamate mutation at residue 600 ((V600E)BRAF). In cells cultured in vitro, (V600E)BRAF is able to stimulate endogenous MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] and ERK phosphorylation leading to an increase in cell proliferation, cell survival, transformation, tumorigenicity, invasion and vascular development. Many of these hallmarks of cancer can be reversed by treatment of cells with siRNA (small interfering RNA) to BRAF or by inhibiting MEK, indicating that BRAF and MEK are attractive therapeutic targets in cancer samples with BRAF mutations. In order to fully understand the role of oncogenic BRAF in cancer development in vivo as well as to test the in vivo efficacy of anti-BRAF or anti-MEK therapies, GEMMs (genetically engineered mouse models) have been generated in which expression of oncogenic BRaf is conditionally dependent on the Cre recombinase. The delivery/activation of the Cre recombinase can be regulated in both a temporal and spatial manner and therefore these mouse models can be used to recapitulate the somatic mutation of BRAF that occurs in different tissues in the development of human cancer. The data so far obtained following Cre-mediated activation in haemopoietic tissue and the lung indicate that (V600E)BRAF mutation can drive tumour initiation and that its primary effect is to induce high levels of cyclin D1-mediated cell proliferation. However, hallmarks of OIS (oncogene-induced senescence) are evident that restrain further development of the tumour.

show abstract

Untitled

Cited by 22 publications

References 25 publications

The Krüppel-associated Box Repressor Domain Can Trigger de Novo Promoter Methylation during Mouse Early Embryogenesis

The Krüppel-associated Box Repressor Domain Can Trigger de Novo Promoter Methylation during Mouse Early Embryogenesis

HIV‐1 alters neural and glial progenitor cell dynamics in the central nervous system: Coordinated response to opiates during maturation

Mouse models for BRAF-induced cancers

Contact Info

Product

Resources

About