PubMed · 8983246
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1996. Cell multiplication.. https://doi.org/10.1016/s0955-0674(96)80094-9
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The p53 protein has been reported to regulate cellular responses to genetic stress such as far-ultraviolet light (UV), protecting human cells from mutation. Levels of p53 protein in hypermutable RSa cells were found here to increase soon after UV irradiation, while those in UV(r)-1 cells, a hypomutable variant of RSa cells, showed a delayed increase. Three cell lines overexpressing wild-type p53 in UV(r)-1 cells exhibited higher sensitivity to UV mutagenicity than did control U-V-7 cells transfected with vector alone, assessed using the ouabain-resistance phenotypic mutation test and identification of K-ras codon 12 base substitution mutation. On the other hand, U-V-7 cells showed UV-induced elevation of antipain-sensitive protease activity, but p53 transfectants did not. Moreover, antipain treatment to U-V-7 cells was increased susceptibility to UV mutagenicity. Thus, p53 protein overproduction may sensitize human cells, at least those tested, to UV mutagenicity, in association with inhibition of protease activity.
By binding to a cis-acting element (oriP) in the Epstein-Barr virus (EBV) genome, EBV nuclear antigen 1 (EBNA1) enables persistence and enhances transcription from EBV episomes. To investigate whether EBNA1 also directly affects cell gene transcription, we conditionally expressed a Flag-tagged dominant negative EBNA1 (FDNE) in an EBV immortalized lymphoblastoid cell line, in which the EBV genome is integrated into cell DNA. FDNE induction inhibited expression from an EBNA1-dependent oriP reporter plasmid by more than 90% in these cells but did not affect expression from integrated EBV or oriP reporter DNA. FDNE induction also did not alter expression of more than 1,800 cellular mRNAs. Lymphoblastoid cell line growth under a variety of conditions was unaffected by FDNE induction. Although Gal4-VP16 and EBNA1 strongly activated and coactivated a Gal4-VP16- and oriP-dependent promoter that was on an episome, only Gal4-VP16 activated the promoter when it was integrated into chromosomal DNA. These data indicate that EBNA1 is specifically deficient in activation of an integrated oriP enhancer and does not affect cell growth or gene expression through an interaction with cognate chromosomal DNA.
The radial pattern of the plant root is determined by the action of two transcription factors, SHORT ROOT and SCARECROW, which are produced in different cell types. The SHORT ROOT protein has now been shown to move from cell to cell, regulating transcription of the downstream SCARECROW gene in the target cells.