DIFFERENTIAL EXPRESSION OF REL FAMILY MEMBERS IN HUMAN T-CELL LEUKEMIA-VIRUS TYPE I-INFECTED CELLS - TRANSCRIPTIONAL ACTIVATION OF C-REL BYTAX PROTEIN

The Tax protein of the human T-cell leukemia virus type I (HTLV-I) has been shown to induce nuclear expression of Rel family NF-kappaB-bindi ng proteins. However, under different experimental conditions, differe nt members of the Rel family were induced (N. Arima, J. A. Molitor, M. R. Smith, J. H. Kim, Y. Daitoku, and W. G. Greene, J. Virol. 65:6892- 6899, 1991). In this study, using specific immunological reagents capa ble of distinguishing individual members of the Rel family proteins, w e show that only c-Rel, not NF-kappaB p50 or p65, is induced in HTLV-I -infected cells. Preferential c-rel induction by HTLV-1 infection was detected at the protein and RNA levels as well as in the nuclear NF-ka ppaB-binding form. Induced c-rel expression was also detected in cells stably transfected with tax cDNA, further correlating the c-rel induc tion with viral Tax expression. An increase in c-rel mRNA was detected within 3 h after induction of Tax expression, suggesting that this ef fect is at least partially regulated at the level of transcription. Fu rthermore, using a particle bombardment method for gene cotransfection , we show that Tax can transcriptionally activate the c-rel promoter i n a T-cell line, Jurkat.