The stimulation of gene expression by the R region from HTLV-1 and BLV

The 5' untranslated regions (5'UTR) of mRNA are known to stimulate or inhib it more or less translation. SR alpha, an association of SV40 early gene pr omoter and of the R region plus the first 39 nucleotides of the U5 region ( designated as R) from the human T-cell leukemia virus (HTLV-1) is currently used to stimulate expression of various coding regions. Its effect is cons idered to take place at the translational level. In all studies published s o far, the R region was associated with the promoter and 5'UTR from SV40 ea rly genes. In the present work, the role of SV40 5'UTR and HTLV-IR region w as evaluated separately using different promoters, reporter genes and cells . Both SV40 5'UTR (SU) and R region (R) from HTLV-1 stimulated separately t he expression of adjacent reporter genes. When associated, the SV40 5'UTR a nd the R region from HTLV-1 (SUR) were a more potent stimulator of gene exp ression and their effects were more than additive. This effect was very pot ent in HeLa and HC11 cells and almost inexistent in CHO and COS 7 cells. It was of various intensity in other cell types including bird and fish cells . The presence of SUR in gene constructs favoured the accumulation of the m RNAs. SUR stimulated gene expression when added between the cap and the ini tiation codon. Unexpectedly, SUR was never inhibitory. SUR can therefore be considered essentially as a potent and specific stimulator of gene express ion favoring mRNA accumulation. (C) 2000 Elsevier Science B.V. All rights r eserved.