Nucleosome structure do affect gene expression. During high gene activity, say transcription, the nucleosome structure has to be relaxed to allow the RNA polymerase and other transcription factors to access to the promoter region and to move smoothly on the DNA strand. In heterochromatin nucleosome, the structure is compact and hence they seems to be dormant functionally where as in euchromatin regions the nucleosome has been observed to be relaxed and hence they are hghly active regions.