Cyclic dinucleotides (CDNs) span a highly pleiotropic class of bacterial second messenger molecules. Their cellular levels are subject to tight regulation by synthesis and breakdown. By binding to their cognate effector proteins or riboswitch RNA, CDNs regulate numerous phenotypic features such as mobility, sessility, biofilm formation and virulence. In addition to a bacterial origin, recent findings suggested CDNs to be synthesized by metazoans metazoan cells, preparing the ground for an upcoming and exciting field of research.
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