Project description:Chromatin proteins competes with the transcription machinery for access to genomic DNA and suppress cryptic promoters. CRISPR arrays form the physical memory of CRISPR adaptive immune systems. The incorporation of virus-derived AT-rich DNA into CRISPR arrays renders them prone to harbouring cryptic promoters. Sulfolobales feature extremely long CRISPR arrays spanning several kilobases as well as a CRISPR-specific chromatin protein termed Cbp1. Altered Cbp1 expression affects transcription from CRISPR arrays in multiple ways, but the mechanistic basis remains to be understood. Here, we show that Cbp1 recruits the general chromatin protein Cren7 to form a heteromeric chromatin complex at CRISPR arrays. Cbp1-CreN7 chromatinisation plays a dual role in the transcription of CRISPR array. It suppresses spurious transcription from cryptic CRISPR array-internal promoters via steric occlusion of the transcription machinery while enhancing transcription from promoters in the CRISPR leaders. Our results show that Cbp1-CreN7 chromatinization drives the coordinated transcription of long CRISPR arrays. Additional binding sites of Cbp1 associated with transposases and the leaders of alternative CRISPR arrays hint on a wider regulatory function of Cbp1 linking defense systems and mobile genetic elements.
Project description:Chromatin proteins competes with the transcription machinery for access to genomic DNA and suppress cryptic promoters. CRISPR arrays form the physical memory of CRISPR adaptive immune systems. The incorporation of virus-derived AT-rich DNA into CRISPR arrays renders them prone to harbouring cryptic promoters. Sulfolobales feature extremely long CRISPR arrays spanning several kilobases as well as a CRISPR-specific chromatin protein termed Cbp1. Altered Cbp1 expression affects transcription from CRISPR arrays in multiple ways, but the mechanistic basis remains to be understood. Here, we show that Cbp1 recruits the general chromatin protein Cren7 to form a heteromeric chromatin complex at CRISPR arrays. Cbp1-CreN7 chromatinisation plays a dual role in the transcription of CRISPR array. It suppresses spurious transcription from cryptic CRISPR array-internal promoters via steric occlusion of the transcription machinery while enhancing transcription from promoters in the CRISPR leaders. Our results show that Cbp1-CreN7 chromatinization drives the coordinated transcription of long CRISPR arrays. Additional binding sites of Cbp1 associated with transposases and the leaders of alternative CRISPR arrays hint on a wider regulatory function of Cbp1 linking defense systems and mobile genetic elements.
Project description:CRISPR-Cas is a prokaryotic adaptive immune system, classified into six different types, each characterised by a signature protein. Type III systems, classified based on the presence of a Cas10 subunit, are rather diverse multi-subunit assemblies with a range of enzymatic activities and downstream ancillary effectors. The broad array of current biotechnological CRISPR applications is mainly based on proteins classified as Type II, however recent developments established the feasibility and efficacy of multi-protein Type III CRISPR-Cas effector complexes as RNA-targeting tools in eukaryotes. The crenarchaeon Saccharolobus solfataricus has two type III system subtypes (III-B and III-D). Here, we report the cryo-EM structure of the Csm Type III-D complex from S. solfataricus (SsoCsm), which uses CRISPR RNA to bind target RNA molecules, activating the Cas10 subunit for antiviral defence. The structure reveals the complex organisation, subunit/subunit connectivity and protein/guide RNA interactions of the SsoCsm complex, one of the largest CRISPR effectors known.
Project description:Some archaea from the genus Sulfolobus are important for bioleaching of copper, where metal resistant microorganisms are required. Biofilm generation is one of the ways microorganisms cope with some stimuli in nature, including heavy metals. The response to external factors, particularly in the biofilm form of life, is still underexplored in archaea. To explore how model thermoacidophilic archaeon Saccharolobus solfataricus faces copper stress during this lifestyle, changes in biofilms were studied using crystal violet staining, confocal fluorescence microscopy, and qPCR approaches. It was found that biofilm formation reached a maximum at 0.5 mM Cu, before starting to decrease at higher metal concentrations. The morphology of biofilms at 0.5 mM Cu was observed to be different, displaying lower thickness, different sugar patterns, and higher amounts of cells compared to standard growing conditions. Furthermore, copA, which is responsive to intracellular Cu concentration, was downregulated in biofilm cells when compared with planktonic cells exposed to the same metal concentration. The latest results suggests that cells in biofilms are less exposed to Cu than those in planktonic culture. In a PolyP-deficient strain, Cu was not able to induce biofilm formation at 0.5 mM. In summary, the findings reported here suggest that the biofilm form of life confers S. solfataricus advantages to face stress caused by Cu.Biofilm formation remains a relatively unexplored topic in archaeal research. Therefore, this knowledge in model organisms such as S. solfataricus, and how they use it to face stress, could be of great importance to engineer organisms with improved capabilities to be applied in biotechnological processes, such as bioleaching of metals.
Project description:In the field of biocatalysis and the development of a bio-based economy, hemicellulases have attracted great interest for various applications in industrial processes. However, the study of the catalytic activity of the lignocellulose-degrading enzymes needs to be improved to achieve the efficient hydrolysis of plant biomasses. In this framework, hemicellulases from hyperthermophilic archaea show interesting features as biocatalysts and provide many advantages in industrial applications thanks to their stability in the harsh conditions encountered during the pretreatment process. However, the hemicellulases from archaea are less studied compared to their bacterial counterpart, and the activity of most of them has been barely tested on natural substrates. Here, we investigated the hydrolysis of xyloglucan oligosaccharides from two different plants by using, both synergistically and individually, three glycoside hydrolases from Saccharolobus solfataricus: a GH1 β-gluco-/β-galactosidase, a α-fucosidase belonging to GH29, and a α-xylosidase from GH31. The results showed that the three enzymes were able to release monosaccharides from xyloglucan oligosaccharides after incubation at 65 °C. The concerted actions of β-gluco-/β-galactosidase and the α-xylosidase on both xyloglucan oligosaccharides have been observed, while the α-fucosidase was capable of releasing all α-linked fucose units from xyloglucan from apple pomace, representing the first GH29 enzyme belonging to subfamily A that is active on xyloglucan.