Cell transactivation

The antiinflammatory effects of statins likely result from their ability to inhibit the formation of mevalonic acid. Downstream products of this molecule include not only the end product, cholesterol, but also several isoprenoid intermediates that covalently modify ( pre-nylate ) certain key intracellular signaling molecules. Statin treatment reduces leukocyte adhesion, accumulation of macrophages, MMPs, tissue factor, and other proinflammatory mediators. By acting on the MHC class II transactivator (CIITA), statins also interfere with antigen presentation and subsequent T-cell activation. Statin treatment can also limit platelet activation in some assays as well. All these results support the concept that in addition to their favorable effect on the lipid profile, statins can also exert an array of antiinflammatory and immunomodulatory actions. 

Alterations to the P53 gene are the most common genetic defects known in cancer [5]. The protein product of P53 is involved in a number of pathways that directly and indirectly lead to apoptosis. Many genes that are involved in apoptosis can be induced by this protein, which is a transcriptional transactivator. The emerging hypothesis is that p53 is a central node of a complex apoptotic network that may function differ ently in diver se cell types and tissues. For example, Bax, the prototype proapoptotic member of the Bcl2 family, can be transcriptionally induced by p53 in certain, but not all, cell types. Like p53, Bax can modulate the extent to which cells are sensitive to apoptosis caused by therapeutic agents. 

RRE decoy CD34+ bone marrow cells Traps Rev and thus inhibits transactivation of HIV-1 gene expression Kohn et al. 1999... 

RevMlO CD34+ bone marrow cells Inhibits HIV-1 Rev-mediated transactivation of HIV-1 gene expression Podsakoff et al. 2005... 

Bai J, Rossi J, Akkina R (2001) Multivalent anti-CCR ribozymes for stem cell-based HIV type 1 gene therapy. AIDS Res Hum Retroviruses 17 385-399 Bai J, Sui J, Zhu RY, TaUarico AS, Gennari F, Zhang D, Marasco WA (2003) Inhibition of Tat-mediated transactivation and HIV-1 replication by human anti-hCychnTl intrabodies. J Biol Chem 278 1433-1442... 

Malim MH, Bohnlein S, Hauber J, CuUen BR (1989) Functional dissection of the HlV-1 Rev transactivator-derivation of a trans-dominant repressor of Rev function. Cell 58 205-214... 

The viral protein Rev may also play a role in HIV-1 latency. Expression of the viral Rev protein is essential for the nuclear export of genomic RNA as well as unspliced and/or singly spliced transcripts (Cullen 2003), which are ultimately translated into structural, regulatory, and enzymatic viral proteins. Retention of Rev and Tat (viral transactivator proteins) transcripts in the nucleus of resting CD4h- T cells from HAART patients (Lassen et al. 2006) might be involved in the maintenance of post-integration latency in these cells. Importantly, this phenomenon is non-existent in activated T cells. 

Cabioglu N, Summy J, Miller C, et al. CXCL-12/stromal cell-derived factor-la transactivates HER2-neu in breast cancer cells by a novel pathway involving src kinase activation. Cancer Res 2005 65 6493-6497. 

Kim, C. H., Kim, H. S., Cubells, J. F., 8c Kim, K. S. (1999). A previously undescribed intron and extensive 5 upstream sequence, but not Phox2a-mediated transactivation, are necessary for high level cell type-specific expression of the human norepinephrine transporter gene. /. Biol. Chem., 274, 6507-18. 

FIGURE 20.2 The involvement of RARE on apo-lO -lycopenoic acid-transactivated RARp expression. Upper panel Diagram of the RARp reporter vector with wild type and mutated R AREs. Lower panel HeLa cells transfected with the RARp reporter vector and an internal control vector were treated with 5 pmol/I. of apo-lO -lycopenoic acid or 1 pmol/L of all-trans retinoic acid for 24h. Luciferase activities were measured by dual-luciferase reporter system. Values are means of SEM of three replicate assays., statistically significantly different, as compared with control in the same group, P < 0.05. (Adapted from Lian, F. et al., Carcinogenesis, 28, 1567, 2007. With permission.)... 

Cenci S, Toraldo G, Weitzmann MN, Roggia C, Gao Y, Qian WP, Sierra O, Pacifici R (2003) Estrogen deficiency induces bone loss by increasing T cell probferation and lifespan through IFN-gamma-induced class II transactivator. Proc Natl Acad Sci USA 100 10405-10410... 

In another recent example, Hashimoto reported photoaffinity experiments on retinoic acid receptors (RAR). Retinoic acid plays a critical role in cell proliferation and differentiation. RARs belong to the superfamily of nuclear/ thyroid hormone receptors. They consist of six transmembrane domains (A-F) which is a general feature of these receptors. The A/B domains have an autonomous transactivation function while the C-domain contains the Zn-finger, which binds to DNA. The large E-domain participates in ligand binding, dimerization, and ligand dependent transactivation. Finally, D- and F-domains help the orientation and stabilization of the E-domain. 

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