Recent research published in the Journal Nature Genetics looked into the effects of promoter shape on promoter evolution and expression noise in animals. As covered in class, a promoter is a portion of DNA at which the process of transcription is initiated. Promoters can fall into two categories, broad or narrow. These categories are what is referred to as the promoter "shape". The published findings indicated that promoter shape not only varies across species but also within individual populations. The model organism used in the study was our old friend Drosophila.
The function of differing promoter shape is not fully understood but the researchers were able to show that shape did not directly relate to transcription levels. Results also indicated that expression noise may play a role in the evolution of promoters. I found a short article here that gives a quick overview of gene expression noise for those interested. Overall this research is important in broadening our understanding of the complex interactions that lead to gene expression at a cellular level.