Structural insights into target DNA recognition and cleavage by the CRISPR-Cas12c1 system.

Cas12c is the recently characterized dual RNA-guided DNase effector of type V-C CRISPR-Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated protein) systems. Due to minimal requirements for a protospacer adjacent motif (PAM), Cas12c is an attractive candidate for genome editing. Here we report the crystal structure of Cas12c1 in complex with single guide RNA (sgRNA) and target double-stranded DNA (dsDNA) containing the 5'-TG-3' PAM.

Functional Features and Current Applications of the RNA-Targeting Type VI CRISPR-Cas Systems.

CRISPR-Cas systems are a form of prokaryotic adaptive immunity that employs RNA-guided endonucleases (Cas effectors) to cleave foreign genetic elements. Due to their simplicity, targeting programmability, and efficiency, single-effector CRISPR-Cas systems have great potential for application in research, biotechnology, and therapeutics. While DNA-targeting Cas effectors such as Cas9 and Cas12a have become indispensable tools for genome editing in the past decade, the more recent discovery of RNA-targeting CRISPR-Cas systems has opened the door for implementation of CRISPR-Cas technology in RNA manipulation.

Mechanistic insights into the R-loop formation and cleavage in CRISPR-Cas12i1.

Cas12i is a newly identified member of the functionally diverse type V CRISPR-Cas effectors. Although Cas12i has the potential to serve as genome-editing tool, its structural and functional characteristics need to be investigated in more detail before effective application. Here we report the crystal structures of the Cas12i1 R-loop complexes before and after target DNA cleavage to elucidate the mechanisms underlying target DNA duplex unwinding, R-loop formation and cis cleavage.

Cryo-electron Microscopy Structure of the Swine Acute Diarrhea Syndrome Coronavirus Spike Glycoprotein Provides Insights into Evolution of Unique Coronavirus Spike Proteins.

Coronaviruses (CoV) have caused a number of major epidemics in humans and animals, including the current pandemic of coronavirus disease 2019 (COVID-19), which has brought a renewed focus on the evolution and interspecies transmission of coronaviruses. Swine acute diarrhea syndrome coronavirus (SADS-CoV), which was recently identified in piglets in southern China, is an alphacoronavirus that originates from the same genus of horseshoe bats as severe acute respiratory syndrome CoV (SARS-CoV) and that was reported to be capable of infecting cells from a broad range of species, suggesting a considerable potential for interspecies transmission. Given the importance of the coronavirus spike (S) glycoprotein in host range determination and viral entry, we report a cryo-electron microscopy (cryo-EM) structure of the SADS-CoV S trimer in the prefusion conformation at a 3.

Molecular Basis of Ubiquitination Catalyzed by the Bacterial Transglutaminase MavC.

The effector MavC is a transglutaminase that carries out atypical ubiquitination of the host ubiquitin (Ub)-conjugation enzyme UBE2N by catalyzing the formation of an isopeptide bond between Gln40 and Lys92, which leads to inhibition of signaling in the NF-κB pathway. In the absence of UBE2N, MavC deamidates Ub at Gln40 or catalyzes self-ubiquitination. However, the mechanisms underlying these enzymatic activities of MavC are poorly understood at the molecular level.

Cryo-EM structures of the human PA200 and PA200-20S complex reveal regulation of proteasome gate opening and two PA200 apertures.

Proteasomes are highly abundant and conserved protease complexes that eliminate unwanted proteins in the cells. As a single-chain ATP-independent nuclear proteasome activator, proteasome activator 200 (PA200) associates with 20S core particle to form proteasome complex that catalyzes polyubiquitin-independent degradation of acetylated histones, thus playing a pivotal role in DNA repair and spermatogenesis. Here, we present cryo-electron microscopy (cryo-EM) structures of the human PA200-20S complex and PA200 at 2.

High-throughput sequencing and analysis of microbial communities in the mangrove swamps along the coast of Beibu Gulf in Guangxi, China.

Mangrove swamp is one of the world's richest and most productive marine ecosystems. This ecosystem also has a great ecological importance, but is highly susceptible to anthropogenic disturbances. The balance of mangrove ecosystem depends largely on the microbial communities in mangrove sediments.

Two HEPN domains dictate CRISPR RNA maturation and target cleavage in Cas13d.

Cas13d, the type VI-D CRISPR-Cas effector, is an RNA-guided ribonuclease that has been repurposed to edit RNA in a programmable manner. Here we report the detailed structural and functional analysis of the uncultured Ruminococcus sp. Cas13d (UrCas13d)-crRNA complex.