New pre-print(s) from the Sternberg Lab in collaboration with @LeifuChangLab! We uncover an unprecedented molecular mechanism of CRISPR-Cas12f-like proteins, which drive RNA-guided transcription independently of canonical promoter motifs. Full story here:

16/16 This work was a big team effort and fun collaboration! Thanks to everyone: Matt, Egill, Tanner, Jing, Zaofeng, Americo, Florian, Hamna, Ryan, Nick, Israel and our stellar mentor Sam for making this project possible!.

Join millions who have switched to Grok.

15/16 In summary, we shed light on the biological role of a naturally occurring version of CRISPR interference (CRISPRi), that emerged in gut-associated bacteria to benefit multiple aspects of their lifestyle.

14/16 The repeated exaptation of TnpB to regulate flagellin suggests strong evolutionary pressure favoring RNA-guided control of flagellin expression, particularly in gut-associated bacterial species.

13/16 In other key members of the human gut microbiome, flagellin-regulating TldRs can be found associated with the translational repressor CsrA. The coordinated action of TldR and CsrA suggests a dual mode of both transcriptional and post-transcriptional gene regulation.

12/16 The extra domain stabilizes the filament by increasing inter-subunit contacts. Structure-guided mutagenesis confirmed that this domain is essential to improve motility of the lysogen. We believe it could similarly explain the decreased activation of TLR5.

11/16 We found that both flagellar filaments have a drastically different structure. The prophage flagellar filament is significantly thicker and presents a surprising mesh-like structure. This is due to the presence of an extra domain in the prophage flagellin.

10/16 To try to link these phenotypic observations, we teamed up once again with @IsraelF96135088 and decided to inspect the structures of the prophage flagellin in comparison to their host counterpart.

9/16 The phenotypic effects of lysogenization result in a consequential ecological outcome: enhanced colonization of the murine gut, illustrating the advantage of flagellar remodeling in a host-associated environment.

8/16 We also find that lysogenic conversion by FRφ reduces activation of TLR5, a receptor that detects flagellin to initiate the immune response, suggesting that lysogenization may facilitate immune evasion.

7/16 We find that lysogenic conversion by FRφ leads to increased motility of the host. Essentially, Enterobacter (and even E. coli actually) swims faster when expressing FliCp instead of FliCh.

6/16 To tackle this question we focused on a clinical isolate of Enterobacter, that natively contains what we now call a Flagellin Remodeling prophage (FRφ), and started our detective work to uncover the potential advantage(s) conferred by the acquisition of this prophage.

5/16 Prophages sometimes provide new traits to their bacterial host, that is called “lysogenic conversion”. Now, why would a phage manipulate the flagellar apparatus of their host? That question is the focus of our new study.

4/16 Strikingly, FliC-associated TldRs are found in prophages and target the promoter of host-encoded FliC. Basically, TldR silences the host FliC (FliCh) and the prophage copy (FliCp) takes over, effectively leading to a remodeling of the host flagellar apparatus.

3/16 Unlike TnpB, which can be found in transposons and in association with transposases, TldR is often found in association with FliC (flagellin), the main subunit of flagellar filaments. Flagella are large appendages used by bacteria for motility.

2/16 Last year we reported the discovery of RNA-guided transcriptional repressors, derived from the Cas12 ancestor TnpB. We called it TldR for “TnpB-like nuclease dead repressors”. Yet, we did not address their actual biological role. More details here:

1/16 New pre-print from the Sternberg Lab!.We uncover how temperate phages can use RNA-guided transcription factors to remodel the flagellar composition of their bacterial host and enhance their fitness. Find the preprint and full story here:

14/16 The repeated exaptation of TnpB to regulate flagellin suggests strong evolutionary pressure favoring RNA-guided control of flagellin expression, particularly in gut-associated bacterial species.

13/16 In other key members of the human gut microbiome flagellin-regulating TldRs can be found associated with the translational repressor CsrA. The coordinated action of TldR and CsrA suggests a dual mode of both transcriptional and post-transcriptional gene regulation.

12/16 The extra domain stabilizes the filament by increasing inter-subunit contacts. Structure-guided mutagenesis confirmed that this domain is essential to improve motility of the lysogen. We believe it could similarly explain the decreased activation of TLR5.

11/16 We found that both flagellar filaments have a drastically different structure. The prophage flagellar filament is significantly thicker and presents a surprising mesh-like structure. This is due to the presence of an extra domain in the prophage flagellin.