摘要
CRISPR-Cas systems provide the small RNA-based adaptive immunity to defend against invasive genetic elements in archaea and bacteria.Organisms of Sulfolobales,an order of thermophilic acidophiles belonging to the Crenarchaeotal Phylum,usually contain both type I and typeⅢCRISPR-Cas systems.Two species,Saccharolobus solfataricus and Sulfolobus islandicus,have been important models for CRISPR study in archaea,and knowledge obtained from these studies has greatly expanded our understanding of molecular mechanisms of antiviral defense in all three steps:adaptation,expression and crRNA processing,and interference.Four subtypes of CRISPR-Cas systems are common in these organisms,including I-A,I-D,Ⅲ-B,andⅢ-D.These cas genes form functional modules,e.g.,all genes required for adaptation and for interference in the I-A immune system are clustered together to form aCas and i Cas modules.Genetic assays have been developed to study mechanisms of adaptation and interference by different CRISPR-Cas systems in these model archaea,and these methodologies are useful in demonstration of the protospacer-adjacent motif(PAM)-dependent DNA interference by I-A interference modules and multiple interference activities byⅢ-B Cmr systems.Ribonucleoprotein effector complexes have been isolated for SulfolobalesⅢ-B andⅢ-D systems,and their biochemical characterization has greatly enriched the knowledge of molecular mechanisms of these novel antiviral immune responses.
基金
grants from the Chinese National Transgenic Science and Technology Program(2019ZX08010003 to QS)
the National Natural Science Foundation of China(31771380 to QS)
the Qingdao Applied Research Fund for postdoctoral researchers(62450079311107 to ZY)
the State Key Laboratory of Microbial Technology and Shandong University。
