Overexpressing eukaryotic translation initiation factor 4E stimulates bovine mammary epithelial cell proliferation.
OBJECTIVE
The eukaryotic translation initiation factor 4E regulates the proliferation of many cell types. In the present study, the effect of its overexpression on the growth of an immortalized bovine mammary epithelial 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 parental cells were also investigated.


METHODS
The cDNA of mouse eukaryotic translation 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 desired time points.


RESULTS
The cells overexpressing wild-type 4E displayed higher growth rates and saturation densities compared to the parental cells (P<0.05), whereas cells expressing mutant 4E showed lower growth rates and saturation densities than the parental controls (P<0.05). The amounts of cyclin D1 mRNA and protein were higher in the wild-type transfectants than in the parental controls, whereas the mutant transfectants contained lower amounts of cyclin D1 mRNA and protein compared to the parental cells.


CONCLUSIONS
Our results suggest that overexpression of eukaryotic translation initiation factor 4E leads to increased cyclin D1 expression at the transcriptional level, which consequently stimulates the proliferation of MAC-T cells.
Long
E
E
Department of Animal Science, Macdonald Campus of McGill University, 21,111 Lakeshore Rd, Quebec, H9X 3V9, Ste-Anne-de-Bellevue, Canada.
Lazaris-Karatzas
A
A
Karatzas
C
C
Zhao
X
X
D000818:Animals; D002417:Cattle; D002455:Cell Division; D002461:Cell Line, Transformed; D016213:Cyclins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004847:Epithelial Cells / Q000502:physiology; D039561:Eukaryotic Initiation Factor-4E; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics*; D008321:Mammary Glands, Animal / Q000166:cytology / Q000502:physiology*; D010448:Peptide Initiation Factors / Q000096:biosynthesis* / Q000235:genetics; D014162:Transfection
D016213:Cyclins; D039561:Eukaryotic Initiation Factor-4E; D010448:Peptide Initiation Factors