The Biology of CRISPR-Cas: Backward and Forward 

 -  Cell, 172(6), p.1239-1259, 2018 .
<br/><br/> In bacteria and archaea, clustered regularly interspaced short palindromic repeats (CRISPR)and CRISPR-associated (Cas)proteins constitute an adaptive immune system against phages and other foreign genetic elements. Here, we review the biology of the diverse CRISPR-Cas systems and the major progress achieved in recent years in understanding the underlying mechanisms of the three stages of CRISPR-Cas immunity: adaptation, crRNA biogenesis, and interference. The ecology and regulation of CRISPR-Cas in the context of phage infection, the roles of these systems beyond immunity, and the open questions that propel the field forward are also discussed. CRISPR-Cas systems provide bacteria and archaea with diverse mechanisms of adaptive immunity, illuminating the evolutionary pressures imposed by selfish genetic elements. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>CRISPR ASSOCIATED PROTEIN<br/>DNA<br/>NUCLEIC ACID<br/>RNA