CHROMOSOMAL INTEGRATION DEPENDENT INDUCTION OF JUNB BY GROWTH-FACTORSREQUIRES MULTIPLE FLANKING EVOLUTIONARILY CONSERVED SEQUENCES

The junB locus contains nine flanking evolutionarily conserved sequenc es (FECS) that share 72% to 91% sequence identity between human and mo use, These FECS encompass the same regions of flanking DNA necessary f or maximal mitogenic induction of junB, Most of the cis elements repor ted to date that affect junB regulation also reside within FECS, These observations suggest that the persistence of FECS through evolution r eflects a necessary role in junB transcriptional regulation, In this r eport, we identify specific regulatory cis elements within junB FECS I I and III and provide a quantitative analysis of the contribution made by these sequences to junB induction, These cis elements include a Se rum Response Element (SRE), two Ets sites previously unrecognized as c ontributing to junB expression, and two novel Ets-linked motifs (ELMs) , In general, mutating any single element significantly impairs junB i nduction, Moreover, the same mutations alter the structure of junB 5' flanking DNA within chromatin, Collectively, these results suggest tha t multiple proteins bound within FECS confederate to form a functional promoter complex, the activity of which is dependent upon a specific chromatin architecture.