Transformation of REF cells by oncogenes E1A and cHa-ras leads to activation of AP-1 factor concomitantly with downregulation of c-fos gene transcription. Here we addressed two issues: (i) how does transcription of Fos/Jun-regulated genes change in the cells lacking Fos-Jun heterodimers; (ii) to which extent HDAC-mediated chromatin reorganization does affect, apart from c-fos, transcription of some other early and late-response genes. To this end, we studied the kinetics of serum-stimulated transcription of c-fos, c-jun, fra-1, egr-1, and cyclinD1 genes, as well as the effects of sodium butyrate, an inhibitor of histone deacetylase activity, on transcription of these genes in normal REF cells and transformants E1A + ras. (C) 2003 Elsevier Science (USA). All rights reserved.