Regulation of cellular phenotype and expression of polyomavirus middle T antigen in rat fibroblasts.

Abstract

Polyoma middle T antigen (mT) was expressed in rat F-111 cells under control of the dexamethasoneregulatable mouse mammary tumor virus promoter. Graded phenotypic responses to levels of mT induction by the hormone were seen, with morphological transformation, focus formation, and anchorage-independent growth requiring increasing levels of mT expression. The ability of different clones to form tumors reflected their maximum level of induction of mT-associated kinase and their ability to grow in soft agar. Expression of transformation parameters and tumorigenicity correlates with the level of mT phosphorylated by pp6O-src in immune complexes and not with the total amount of mT determined by metabolic labeling. We suggest that cellular factors regulate mT activity by forming a kinase-active fraction of mT molecules that controls the transformed state.

Mapping of polyomavirus middle T domain that is responsible for AP-1 activation

“…While LT seems to be essential for immortalization of primary cell lines in culture, MT alone can induce morphological transformation and alterations in the growth properties of established cell lines (Schlegel and Bejamin, 1978;Raptis et al, 1985;Cherington et al, 1986). The ST antigen was shown to be non-essential for cell transformation but to induce cell proliferation to higher saturation densities (Cherington et al, 1986).…”

Tumor induction by a transformation-defective polyoma virus mutant blocked in signaling through Shc

“…Middle T is the major transforming protein of polyoma as revealed in various cell transformation assays (4,5). Its actions are mediated through formation of complexes with pp60 c-src .…”

Rodent fibroblast model for studies of response of malignant cells to exogenous 5-aminolevulinic acid

“…Immortalized fibroblast cell lines (Balb/c 3T3, NIH 3T3 and Swiss 3T3), Balb/c mouse fibrosarcoma cell lines (Wehi 164,6418 and 6423), human bladder carcinoma cell line T24 and human lung cancer cell line A549 were purchased from the American Type Culture Collection (ATCC, Rockville, MD, USA). The Fischer rat fibroblast line F-111 and its derivatives PyF-111 (F-111 transformed by polyomavirus infection), mT-2 (F-111 transfected with polyomavirus mT antigen oncogene), Gen-1 (F-111 transfected with polyomavirus early region mT cDNA under the control of the mouse mammary tumour virus MMTV promoter), pymT4d (F-111 transfected with polyoma mT under the control of the polyomavirus promoter), Fneo-1v and Fneo-1w (F-111 cells transfected with the G418-resistance gene alone) were described previously (Raptis et al, 1985). Primary .…”