THE DEVELOPMENTAL ACTIVATION OF THE CHICKEN LYSOZYME LOCUS IN TRANSGENIC MICE REQUIRES THE INTERACTION OF A SUBSET OF ENHANCER ELEMENTS WITH THE PROMOTER

The complete chicken lysozyme locus is expressed in a position indepen dent fashion in macrophages of transgenic mice and forms the identical chromatin structure as observed with the endogenous gene in chicken c ells. Individual lysozyme cis-regulatory elements reorganize their chr omatin structure at different developmental stages, Accordingly, their activities are developmentally regulated, indicating a differential r ole of these elements in locus activation. We have shown previously th at a subset of enhancer elements and the promoter are sufficient to ac tivate transcription of the chicken lysozyme gene at the correct devel opmental stage, Here, we analyzed to which grade the developmentally c ontrolled chromatin reorganizing capacity of cis-regulatory elements i n the 5'-region of the chicken lysozyme locus is dependent on promoter elements, and we examined whether the lysozyme locus carries a domina nt chromatin reorganizing element, To this end we generated transgenic mouse lines carrying constructs with a deletion of the lysozyme promo ter, Expression of the transgene in macrophages is abolished, however, the chromatin reorganizing ability of the cis-regulatory elements is differentially impaired, Some cis-elements require the interaction wit h the promoter to stabilize transcription factor complexes detectable as DNase I hypersensitive sites in chromatin, whereas other elements r eorganize their chromatin structure autonomously.