FIG 1.

HEK TER anchorage independence transformation assay. (A) The HEK TER cell-based system was used to determine whether papillomavirus oncoproteins can replace SV40 ST antigen in cells expressing SV40 large T antigen, hTERT, and activated Ras (14). HEK TER cells were transduced with pMIG-based retroviruses, which consist of a test oncoprotein gene located upstream of the EMCV IRES and a GFP open reading frame. Test oncoproteins included wild-type SV40 ST, the SV40 ST110 mutant, HPV16 E6, HPV16 E7, BPV1 E6, and BPV1 E7. GFP-positive cell populations were sorted by FACS and tested for growth in soft agar. LTR, long terminal repeat. (B) HEK TER cells were transduced with pMIG retroviruses encoding SV40 small T antigen (SV40 ST), HPV16 E6, HPV16 E7, BPV1 E6, or BPV1 E7. The various panels depict phase-contrast and green fluorescence images of HEK TER cell lines after sorting and expansion. Mock-transduced HEK TER cells were included as a control but were not sorted. (C) In a separate set of transductions, HEK TER cells were transduced with a pMIG vector encoding the SV40 ST110 mutant or with an empty version of the pMIG vector. Images depict phase-contrast and green fluorescence images of HEK TER cell lines after sorting and expansion. HEK TER parental cells are included as a control but were not sorted.