SF-B that binds to a negative element in glutathione transferase P gene is similar or identical to trans-activator LAP/IL6-DBP.

We have previously identified a silencer (negative enhancer) in glutathione transferase P (GST-P) gene which is strongly and specifically induced during hepatocarcinogenesis of the rat. At least three trans-acting factors bind to multiple cis-elements located in this silencer. One of these factors, SF-B (Silencer Factor B) specifically binds to GPS1 (GST-P Silencer 1) and has been cloned by a Southwestern protocol. Analysis of DNA and deduced amino acid sequence reveals that SF-B clone is most likely identical to an IL-6 inducible trans-activator LAP/IL6-DBP. Binding efficiency of SF-B to GPS1 is indistinguishable from that to IL6-responsive element found in C-reactive protein gene. The possibility that SF-B/LAP/IL6-DBP functions as a dual positive and negative regulator is discussed.