Only few of the human endogenous retrovirus (HERV) sequences in the human genome can produce proteins. We have previously reported that (i) patients with germ cell tumors often make antibodies against proteins encoded by HERV-K elements, (ii) expression of the HERV-K rec gene in transgenic mice can interfere with germ cell development and induce carcinoma in situ, and (iii) HERV-K np9 transcript is overproduced in many tumors including breast cancers. Here we document that both Np9 and Rec physically and functionally interact with the promyelocytic leukemia zinc finger (PLZF) tumor suppressor, a transcriptional repressor and chromatin remodeler implicated in cancer and the self-renewal of spermatogonial stem cells. Interaction is mediated via two different central and C-terminal domains of Np9 and Rec and the C-terminal zinc fingers of PLZF. One major target of PLZF is the c-myc proto-oncogene. Coexpression of Np9 and Rec with PLZF abrogates the transcriptional repression of the c-myc gene promoter by PLZF and results in c-Myc overproduction, altered expression of c-Myc-regulated genes, and corresponding effects on cell proliferation and survival. Thus, the human endogenous retrovirus proteins Np9 and Rec may act oncogenically by derepressing c-myc through the inhibition of PLZF.

We have recently identified Np9 as a novel nuclear protein produced by the human endogenous retrovirus K and were able to document the exclusive presence of np9 transcript in tumors and transformed cells. With the aim of studying whether Np9 has a role in tumorigenesis, a systematic search for interacting proteins was performed. Here, we identify the RING-type E3 ubiquitin ligase LNX (ligand of Numb protein X) as an Np9-interacting partner. We furthermore show that the interaction involves N-and C-terminal domains of both proteins and can affect the subcellular localization of LNX. LNX has been reported to target the cell fate determinant and Notch antagonist Numb for proteasome-dependent degradation, thereby causing an increase in transactivational activity of Notch. We document that LNX-interacting Np9, like Numb, is unstable and degraded via the proteasome pathway and that ectopic Numb can stabilize recombinant Np9. Combined, these findings point to the possibility that Np9 affects tumorigenesis through the LNX/Numb/Notch pathway.Up to 8% of the human genome consists of retrovirusderived sequences (19). They are the result of numerous infections and subsequent integration of proviral elements into the germ line of human ancestors during the past 40 million years (2). Most of the recent human endogenous retrovirus (HERV) elements are defective due to the accumulation of mutations. Nonetheless, retroviral genes are frequently expressed in normal and transformed human tissues. The function of these genes in normal human cell physiology is still unclear (32). So far, only the expression of the env gene of HERV-W is known to have a crucial function in normal organismal physiology, namely human trophoblast cell fusion and differentiation (5,12,23). In contrast, retroviral gene expression has been linked to several human diseases, including tumorigenesis. In particular, expression of HERV-K seems to be strongly associated with transformation. Early hints pointing in this direction came from the observation that expression of the HERV-K proteins Gag and Env, as well as antibodies directed against these proteins, could be specifically detected in patients suffering from germ cell tumors (17,24,30,31). Other studies implicate a contribution of HERV-K10 gag RNA expression to the development of leukemia (9) or show that env as well as the expression of subgenomic env transcripts correlates with human breast cancer (35,36).It is unclear, at the present, how these proteins may support tumorigenesis. The Rev-like regulatory protein Rec (20,21)

Background: Mutation of a tumor suppressor allele leaves the second as backup. Not necessarily so with p53. This homo-tetrameric transcription factor can become contaminated with mutant p53 through hetero-tetramerization. In addition, it can be out-competed by the binding to p53 DNA recognition motifs of transactivation-incompetent isoforms (ΔN and ΔTA-isoforms) of the p53/ p63/p73 family of proteins. Countermeasures against such dominant-negative or dominantinhibitory action might include the evolutionary gain of novel, transactivation-independent tumor suppressor functions by the wild-type monomer.

Micropatterned adhesive surfaces may have potential in reconstructive surgery. The adhesion performance of mice ear skin to micropatterned poly(dimethylsiloxane) (PDMS) was investigated, under in vitro conditions, and compared to flat substrates. No significant difference in separation force F was observed between flat substrates and micropatterned surfaces with pillar arrays. However, the energy necessary for separation of the substrate from the skin was sensitive to the topography. Furthermore, our results show that the force-displacement curves depended on the wetness of the skin: Highest force values were obtained for fresh skin while the forces decreased as the skin dried out. The results are encouraging for further studies on the potential of patterned PDMS in biomedical applications.