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ABSTRACT: Transformed cells express high levels of non-telomeric reverse-transcriptase (RT) activity of retrotransposon and endogenous retrovirus origin. We previously reported that RT inhibition, either pharmacological or through transient silencing of RT-encoding LINE-1 (L1) elements by RNA interference (RNAi), reduced proliferation, induced differentiation and reprogrammed gene expression in human tumorigenic cell lines. Moreover, the antiretroviral drug efavirenz antagonized tumor progression in animal models in vivo. To get insight into the role of retroelements in tumorigenesis, we have now produced two cell lines derived from A-375 melanoma, in which the expression of either L1 retrotransposon, or HERV-K endogenous retrovirus, was stably suppressed by RNAi. Compared to the parental A-375 cell line, cells with stably interfered L1 expression show a lower proliferation rate, a differentiated morphology and lower tumorigenicity when inoculated in nude mice. L1 silencing modulates expression of several genes and, unexpectedly, also downregulates HERV-K expression. In HERV-K interfered cells, instead, L1 expression was unaffected, and cell proliferation and differentiation remained unchanged compared to parental A-375 cells. In vivo, however, their tumorigenic potential was found to be reduced after inoculation in nude mice. These results suggest that L1 and HERV-K play specific and distinct roles in cell transformation and tumor progression.
Oncogene 07/2007; 26(29):4226-33. · 6.37 Impact Factor
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ABSTRACT: We previously characterized a nuclease-hypersensitive fraction of mouse sperm chromatin, which is organized in a typical nucleosomal structure. A partial genomic library was constructed with the DNA from the nuclease-hypersensitive chromatin, which revealed a high content in retroposon/retroviral DNA sequences. Here we report that the cloned nuclease-hypersensitive DNA also contains clusters of potential sites for transcription factors: among those, binding sites for Oct-1, Oct-4, TBP, Ets-1, and C/EBP are most abundant. This observation prompted us to ask whether mature spermatozoa contain the corresponding protein factors. Indirect immunofluorescence experiments show that all analyzed factors are indeed present in the sperm heads. Moreover, transcription factors are associated with the nuclease-hypersensitive chromatin of spermatozoa, as endogenous nucleases that degrade the hypersensitive fraction also cause the concomitant release of transcription factors from sperm cells into the medium. Band-shift assays with proteins extracted from the supernatant, and immunofluorescence analysis of sperm pellets, indicate that transcription factors are largely recovered in the supernatant while being absent or poorly retained in spermatozoa. The possible involvement of these factors in early embryogenesis is discussed.
Molecular Reproduction and Development 10/2001; 60(1):97-106. · 2.53 Impact Factor
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ABSTRACT: Human lymphoblastoid cells of normal origin and from genetic instability syndromes, i.e. Fanconi anemia (FA) group C and ataxia telangectasia, were continuously exposed to extremely low frequency magnetic field (ELF-MF). We report that ELF-MF, though not perturbing cell cycle progression, increases the rate of cell death in normal cell lines. In contrast, cell death is not affected in cells from genetic instability syndromes; this reflects a specific failure of the apoptotic response. Reintroduction of complementation group C in FA cells re-established the apoptotic response to ELF-MF. Thus, genes implicated in genetic instability syndromes are relevant in modulating the response of cells to ELF-MF.
FEBS Letters 02/2001; 487(3):397-403. · 3.54 Impact Factor
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ABSTRACT: We have tested three parameters in sperm-mediated gene transfer assays with mice and pigs: (i) the epididymal versus ejaculated origin of sperm cells, (ii) the primary structure, and (iii) the amount of the challenging foreign DNA. We have found that the pVLCNhGH construct, of retrotransposon origin, causes a massive embryo lethality and yet increases the yield of genetic transformation among born animals of both species compared to viral constructs. Arrest of embryonic development is a DNA dose-dependent effect, which is observed with high DNA doses, while lower doses are compatible with development. Finally, the overall efficiency of sperm-mediated gene transfer is higher when ejaculated, versus epididymal, spermatozoa are used. We suggest that this difference is related to the highly efficient apoptotic response in epididymal compared to ejaculated spermatozoa, triggered by the interaction of exogenous DNA molecules with the sperm membrane.
Molecular Reproduction and Development 07/2000; 56(2 Suppl):301-5. · 2.53 Impact Factor
