Feels awkward but necessary to celebrate scientific progress in this imperiled time for US biomedical research.

Proud of our latest paper out today exploring the role of transposable elements in antiviral resistance to HIV 🦠

genomebiology.biomedcentral.com/articles/10....
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CRISPR-Cas systems are common in chromosomes and mobile plasmids. Therefore, targeting arrays would provide a stable integration position facilitating vertical transmission while maintaining the ability to mobilize between bacteria for horizontal transmission. 10/10

We did not find significant array degradation downstream the insertion. We suspect that integrating into a spacer in the arrays and keeping a small size allow these elements to not disrupt CRISPR-Cas system function. 9/10

Aligning the DNA sequences that flank the ends of the tRNA- and array-targeting elements revealed a conserved DNA motif 40 to 50 bp away from the transposons left ends. 8/10

Unlike the tRNA-targeting pathway from the closely related McCAST element, the array targeting element was not functional in E. coli and may need host factors not found in this heterologous host. 7/10

AlphaFold3-generated structures of TnsD proteins from A. franciscana (AfTnsD, array-targeting) and M. californica (McTnsD, tRNA-targeting) suggest that the C-terminal region absent in AfTnsD corresponds to a helix-turn-helix domain (HTH) used for DNA binding. 6/10

Unlike most Tn7-like elements, array-targeting transposons do not accumulate cargo genes, being consistently smaller and simpler. This contrasts with what is found even with the closely related tRNA-targeting elements. 5/10

A distinct structural difference that co-occurs with the change in att site used between these two elements is a C-terminal motif found in the tRNA-targeting TnsD proteins that is absent in the array-targeting group. 4/10

A similarity tree of nonredundant TnsD/TniQ proteins revealed that the array-targeting transposons are phylogenetically close to TnsD-mediated tRNA-targeting transposons in this phylum, a group that includes validated I-D and I-B2 CAST. 3/10

We found a novel family of Tn7-like transposable elements in Cyanobacteria which display a preference for insertion within CRISPR arrays, suggesting a previously unrecognized functional interplay between Tn7-like elements and CRISPR-Cas systems. 2/10

Our preprint describing a family of Tn7-like transposons that evolved to target CRISPR repeats is now published at Mobile DNA #Tn7 #transposons #mobileDNA 1/10
mobilednajournal.biomedcentral.com/articles/10....