Alternatively, these proteins may not necessarily contribute to intracellular bacterial growth, the most common phenotype examined in the study of L. pneumophila pathogenesis. Instead, they may help the host adapt to challenges such as those brought by detrimental environmental changes and the fluctuations in nutrient supplies. Regardless of the reason, future studies directed to the elucidation of the biochemical and cell biological activities of these substrates will undoubtedly contribute greatly to our understanding the biology of both the pathogen and its hosts. The sequencing and current annotation of the human Pazopanib genome revealed that it contains about 21500 protein coding genes . However, the overwhelming majority of the human genome is composed of non-coding DNA whose function has not been thoroughly investigated. Interestingly, approximately 5% of the human genome is conserved in other eutherian mammals. The recent analysis of DNA topography conservation, rather than nucleotide sequence, suggested that up to 12% of the human genome could be under evolutionary constraint. A significant number of CNCs are found in gene-poor regions of the genome, suggesting that these large intergenic regions have maintained a function throughout evolution. The function of most CNCs remains elusive although recent studies have begun to assign function to a fraction of them. Some CNCs appear to be transcriptional enhancers in vivo although their deletion does not appear to be detrimental for mouse development in one study, despite evidence that CNCs are maintained by negative selective pressure. However, the importance of CNCs in disease has been documented in several disorders including preaxial polydactyly, human NSCL/P holoprosencephaly and Pierre Robin sequences . Furthermore, CNCs might act as silencer elements. It was also proposed by computational analysis that as much as 10% of CNCs correspond to matrix-attachment regions . Finally CNCs might be involved in other cellular processes that remain to be determined. Mostfunctional studies of CNCs performed to date utilized various enhancer essays in order to test their potential role in gene regulation. Although successful, these approaches are not suited for the determination of the functions of CNCs that do not behave as transcriptional enhancers and provide little information on the genes they regulate, as enhancers can act over long distances. Here, we took a different approach aimed at the analysis of physical interactions between CNCs and the rest of the genome using circular chromosome conformation capture . We argue that the identification of “CNC interacting regions” could provide valuable information on the function of the tested CNCs and on the target genomic regions they interact with. In this paper we describe the CIRs of 10 CNCs from human chromosome 21. Conservation of DNA elements by negative selection, such as CNCs, suggests that these sequences have maintained a function during evolution.