SV40 LARGE-T ONCOGENE INHIBITS TRANSCRIPTION OF PERLECAN-RELATED PROTEOGLYCANS BUT STIMULATES HYALURONAN SYNTHESIS IN A TEMPERATURE-SENSITIVE RENAL-TUBULE PRINCIPAL CELL-LINE

We have analyzed the effects of SV40 large-T oncogene on proteoglycan (PG) synthesis in a temperature-sensitive SV40-transformed renal cell line. Cells shifted from permissive (33 degrees C) to restrictive (39. 5 degrees C) temperature, acquired within 48 h the phenotype of princi pal cells of the renal collecting tubule. They then synthesized hyalur onan, a large-sized PG, small amounts of free GAG chains, and a major similar to 130-kDa kDa heparan sulfate-PG. Sulfated PGs were localized in a basement membrane-like layer and possessed the same core protein (61-70 kDa) derived from perlecan. Expression of large-T oncogene at the permissive temperature induced dramatic alterations of the extrace llular matrix, and a 4- and 12 fold reduction in cell-associated and m edium-released sulfated PGs, due to a similar to 50% decrease in perle can mRNA content and gene transcription. This contrasted with a 2-fold increase in actin gene transcription and a 10- and 2-fold rise in the hyaluronan content in cells and medium, respectively. These alteratio ns did not occur in a control cell line (RC.SV3) derived from the same tubule segment but infected with wild-type SV40 strain. They are thus most likely related to the functional state of large-T oncogene and m ay take part in the early steps of transformation.