The first conference of the year brought together cryo-EM academic communities and industry partners to evaluate how the use of cryo-EM has developed over the last decade.

The researchers provided updates on recent and ongoing methodological developments and focused on the integration of cryo-ET and cryo-EM with complementary imaging techniques and discussed the integration of cryo-EM in the drug-discovery workflow.

In addition to the conference pogramme showcasing speakers from many different countries and working across various fields, we also held a poster session, where conference participants got to vote for the best poster prizes resulting in two winners.

Viktoras Ragožius is one of them and we are happy to share his abstract below. Take a look!

Structural studies of type I CRISPR-Cas adaptation complex interaction with prespacers

Presenter: Viktoras Ragožius, Vilnius University, Lithuania

Collaborators: Inga Songailiene, Tomas Sinkunas, Algirdas Miksys, Virginijus Siksnys, Lina Malinauskaite, Vilnius University, Lithuania

Abstract: Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) proteins provide an adaptive immunity against exogenous nucleic acids (NA) in bacteria and archaea. CRISPR-Cas systems retain a record of past infections by incorporating short segments of foreign NA as spacers within the host CRISPR array in a process known as adaptation.

Adaptation stage requires a multistep process, starting with obtaining a pool of possible DNA substrates for the adaptation complex and completing with integration of prespacers into CRISPR locus in a correct orientation to enable biogenesis of functional crRNA molecules, that are vital for the RNA-guided interference pathways.

Heterohexameric complex composed of Cas1 and Cas2 proteins (adaptation complex) identifies a potential prespacer by recognizing a specific 2-5 base pairs sequence known as protospacer adjacent motif (PAM). Within type I systems, PAM recognition can be achieved either directly through the adaptation complex or with the involvement of Cas4

(PAM-cleaving endonuclease). The coordination of PAM processing with stepwise integration is important to establish unidirectionality of prespacer’s insertion into CRISPR array.

Nonetheless, this mechanism has been more extensively investigated in systems that include Cas4, as opposed to systems where adaptation complex directly recognizes the PAM. Here, single particle transmission electron cryo-microscopy was used to determinestructures of type I adaptation complex interaction with different prespacers.

This study provides important insights into the molecular basis of adaptation stage based on prespacers processing.

Poster not available due to unpublished data.

The EMBL Industry Workshop ‘Cryo-EM in academia and industry’ took place from 29 – 31 January 2024 at EMBL Heidelberg and virtually.