The double helix DNA structure most of us are familiar with is encoded with copious amounts of information. Yet, all of this “junk” DNA has been deemed useless until recently, when researchers captured video showing how pieces of this so-called junk DNA can act as on/off switches for genes.
Over 90 percent of the human genome consists of non-genes, which are often referred to as the junk DNA, and until recently, scientists had no idea how these “junk” bits could turn on or off genes. But new research shows that these regions of “junk” DNA are teeming with functional activity and can be activated by the presence of specific proteins.
To understand how this works, researchers examined the binding of a protein called p460 to DNA. They found that this protein, which is involved in DNA-dependent protein kinase, is required to activate DNA-dependent gene transcription. They also found that p460 is specifically bound to the ends of double-stranded DNA, whereas supercoiled DNA and single-stranded DNA in the form of poly(dA) or poly(dT) fail to activate p460.
The binding of p460 to the ends of double-stranded and supercoiled DNA is mediated by distinct sets of chromosome-specific proteins. The cis-acting domains of these proteins interact with distinct motifs present in the promoter regions of DNA-dependent genes to trigger their activation. The data suggest that the choice of which DNA replication origins are activated during S phase is regulated by factors that regulate chromatin organization, cell growth and differentiation, and replication stress. dna activation