Overexpressing eukaryotic translation initiation factor 4E stimulates bovine mammary epithelial cell proliferation

Background and aims: The eukaryotic translation initiation factor 4E regula tes the proliferation of many cell types. In the present study, the effect of its overexpression on the growth of an immortalized bovine mammary epith elial cell line, MAC-T, has been investigated. Since involvement of cyclin D1 in growth regulation of other cell types has been suggested previously, the differences in cyclin D1 expression among the 4E-overexpressing and par ental cells were also investigated. Methods: The cDNA of mouse eukaryotic t ranslation initiation factor 4E coding region (either wild-type or mutant, where Trp-56 was mutated to Ala) was transfected into MAC-T cells: and its protein expression was detected by Western blot analysis. Growth rates and saturation densities were calculated based on the cell counting data at des ired time points. Key results: The cells overexpressing wild-type 4E displa yed higher growth rates and saturation densities compared to the parental c ells (P < 0.05), whereas cells expressing mutant 4E showed lower growth rat es and saturation densities than the parental controls (P < 0.05). The amou nts of cyclin D1 mRNA and protein were higher in the wild-type transfectant s than in the parental controls, whereas the mutant transfectants contained lower amounts of cyclin D1 mRNA and protein compared to the parental cells . Conclusion: Our results suggest that overexpression of eukaryotic transla tion initiation factor 4E leads to increased cyclin D1 expression at the tr anscriptional level, which consequently stimulates the proliferation of MAC -T cells. (C) 2001 Elsevier Science Ltd. All rights reserved.