Immortalization
Mostrando 13-24 de 349 artigos, teses e dissertações.
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13. Dissociation among in vitro telomerase activity, telomere maintenance, and cellular immortalization
The immortalization of human cells is a critical step during tumorigenesis. In vitro, normal human somatic cells must overcome two proliferative blockades, senescence and crisis, to become immortal. Transformation with viral oncogenes extends the life span of human cells beyond senescence. Such transformed cells eventually succumb to crisis, a period of wide
The National Academy of Sciences.
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14. Disruption of either the E1 or the E2 regulatory gene of human papillomavirus type 16 increases viral immortalization capacity.
The "high-risk" human papillomavirus types 16 (HPV-16) and 18 (HPV-18) have been etiologically implicated in the majority of human cervical carcinomas. In these cancers, the viral DNAs are often integrated into the host genome so that expression of the E1 and the E2 genes is lost, suggesting that disruption of these regulatory genes plays an important role i
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15. The E7 gene of human papillomavirus type 16 is sufficient for immortalization of human epithelial cells.
The contribution of the E6 and E7 open reading frames of human papillomavirus type 6b (HPV6b) and HPV16 to immortalization of human keratinocytes was evaluated by using amphotropic recombinant retroviruses. The HPV16 E7 gene could immortalize primary human keratinocytes without the cooperation of the viral E6 gene; however, E6 was able to contribute signific
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16. Telomere elongation in immortal human cells without detectable telomerase activity.
Immortalization of human cells is often associated with reactivation of telomerase, a ribonucleoprotein enzyme that adds TTAGGG repeats onto telomeres and compensates for their shortening. We examined whether telomerase activation is necessary for immortalization. All normal human fibroblasts tested were negative for telomerase activity. Thirteen out of 13 D
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17. The EBNA2 Polyproline Region Is Dispensable for Epstein-Barr Virus-Mediated Immortalization Maintenance
Epstein-Barr virus nuclear antigen 2 (EBNA2) is required for EBV-mediated immortalization of primary human B cells and is a direct transcriptional activator of viral and cellular genes. The prototype EBNA2 protein contains a unique motif in which 43 out of 45 amino acids are prolines (polyproline region [PPR]). Previous genetic analysis has shown that deleti
American Society for Microbiology.
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18. Immortalization-susceptible elements and their binding factors mediate rejuvenation of regulation of the type I collagenase gene in simian virus 40 large T antigen-transformed immortal human fibroblasts.
Dramatic changes occur in expression of the type I collagenase gene during the process of immortalization in simian virus 40 large T antigen-transformed human fibroblasts (S. Imai and T. Takano, Biochem. Biophys. Res. Commun. 189:148-153, 1992). From transient transfection assays, it was determined that these changes involved the functions of two immortaliza
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19. Polyomavirus large T mutants affected in retinoblastoma protein binding are defective in immortalization.
To clarify the relationship between the various activities of the polyomavirus large T antigen and the contribution of this oncogene to neoplastic transformation, we constructed a series of mutants with small deletions or single-amino-acid substitutions in two separate regions of the protein. These sequences were targeted because they showed considerable sim
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20. Immortalization of primary epithelial cells requires first- and second-exon functions of adenovirus type 5 12S.
Immortalization of primary cells is a multistep process. The adenovirus E1A 12S gene product is a member of the class of oncoproteins that have the ability to establish primary cells as cell lines in culture. It is encoded by two exons. Extensive mutational analysis demonstrates that four regions of the E1A 12S gene, encoded by both exons, are necessary for
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21. Regions of human papillomavirus type 16 E7 oncoprotein required for immortalization of human keratinocytes.
Binding of the retinoblastoma gene product (pRB) by viral oncoproteins, including the E7 of human papillomavirus type 16 (HPV 16), is thought to be important in transformation of cells. One of the steps in transformation is the immortalization process. Here we show that mutations in E7 within the full-length genome which inhibit binding of pRB do not abrogat
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22. Conditional immortalization of freshly isolated human mammary fibroblasts and endothelial cells
Reports differ as to whether reconstitution of telomerase activity alone is sufficient for immortalization of different types of human somatic cells or whether additional activities encoded by other “immortalizing” genes are also required. Here we show that ectopic expression of either the catalytic subunit of human telomerase (hTERT) or a temperatu
The National Academy of Sciences.
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23. Human Papillomavirus Type 16 E6-Induced Degradation of E6TP1 Correlates with Its Ability To Immortalize Human Mammary Epithelial Cells
Recent analyses have identified a number of binding partners for E6, including E6AP, ERC55, paxillin, hDlg, p300, interferon regulatory factor 3, hMCM7, Bak, and E6TP1. Notably, association with E6 targets p53, E6TP1, myc, hMCM7, and Bak for degradation. However, the relative importance of the various E6 targets in cellular transformation remains unclear. E6
American Society for Microbiology.
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24. Immortalization of primary human keratinocytes by the helix–loop–helix protein, Id-1
Basic helix–loop–helix (bHLH) DNA-binding proteins have been demonstrated to regulate tissue-specific transcription within multiple cell lineages. The Id family of helix–loop–helix proteins does not possess a basic DNA-binding domain and functions as a negative regulator of bHLH proteins. Overexpression of Id proteins within a variety of cell types h
The National Academy of Sciences.