PA317 cyclin E-L is an amphotropic retrovirus producing cell line constructed from the PA317 (see ATCC CRL-9078) fibroblast cell line by introduction of a retrovirus expression vector (LXSN). The LXSN vector uses the 5'long terminal repeat of Moloney murine sarcoma virus to express the inserted cDNA and contains the neomycin phosphotransferase gene (G418 resistance) as a selectable marker. The full length cDNA coding human cyclin E-L (1.7 kb HindIII fragment) was treated with Klenow fragment and cloned into the HpaI site of the vector. The PA317 cyclin E-L cell line expresses human cyclin E-L. Cyclin E is a nuclear protein essential for the G1 to S phase transition. Mammalian cells express two forms of cyclin E protein which differ from each other by the presence (cyclin E-L) or absence (cyclin E-S) of a 15 amino acid amino terminal domain. Fibroblasts engineered to constitutively overexpress either form of cyclin E show elevated cyclin E dependent kinase activity and a shortened G1 phase of the cell cycle. |
