Regulation of gene expression: probing DNA-protein interactions in vivo and in vitro

Tremendous efforts have been put together over the last several years to complete the entire sequencing of the human genome. As we enter the proteomic era, when the major aim is understanding which gene encodes which protein, the time has also come to identify their precise function inside the astonishing signaling network required to accomplish all cellular functions. Understanding when, why and how a gene is expressed has now become a necessity toward identifying all the regulatory pathways that mediate cellular processes such as differentiation, migration, replication, DNA repair and apoptosis. Regulation of gene transcription is a process that is primarily under the influence of nuclear-located transcription factors. Consequently, identifying which protein activates or represses a specific gene is a prerequisite for understanding cell fate and function. The current state of, and recent advances in, transcriptional regulation approaches are reviewed here, with special emphasis on new technologies required when probing for DNA-protein interactions. This review explores different strategies aimed at identifying both the regulatory sequences of any given gene and the trans-acting regulatory factors that recognize these elements as their target sites in the nucleus. Ongoing developments in the fields of nanotechnology, RNA silencing and protein modeling toward the investigation of DNA-protein interactions and their relevance in the battle against cancer are discussed.