A cyclic dinucleotide comprised of GMP and AMP was previously shown to be a key intermediate during activation of innate immune responses to cytosolic DNA.A report by Patel and Tuschl groups published in Cell reveals the structure of the enzyme involved in the synthesis of this second messenger and identifies this cyclic dinucleotide as a unique compound in metazoan cell signaling.
For more than 100 years it has been known that DNA stimulates immune responses [1].Hence,when DNA reaches the cytoplasmic compartment in a cell,no matter originating from an infectious agent like viruses or from the damaged nucleus or mitochondria,it is recognized as a sign of danger.DNA can provoke severe consequences as it can be seen from aberrant recognition of lost DNA in autoimmune conditions such as systemic lupus erythematous and Sjogren's syndrome.To perceive such a dreadful insult,several DNA-sensing proteins are present in mammalian cells.