With ~1/3 of Streptomyces genomes carrying telomeric transposons, these elements compete for the same niche. Identical transposons in different telomeres, both within and between genomes, are occasionally found to be disrupted by other transposons, indicating fierce competition.

TnsBC telomeric transposons are highly diverse, with distinct gene repertoires. Surprisingly, one subgroup includes the Type I-E Cascade + tnsBC system. The tnsBC was initially thought to replace Cas1-Cas2. Spacer analysis supports their telomeric role, often targeting ttrA.

Tn7-like telomeric transposons encode TnsA, which mediates cointegrate resolution. We hypothesized TnsA is inactive, as cut-and-paste transposition would harm one-ended transposons. Active site analysis confirmed that conserved residues in non-telomeric transposons are altered.

Following PASTs, we searched telomeric transposons by clustering and mapping the locations and orientations of DDE family transposases in Streptomyces. This analysis identified two groups of telomeric transposons: Tn7-like and the other containing only conserved tnsB and tnsC.

Initially mistaken as "broken" V-K CASTs near contig ends, PASTs are linked to a small protein gene and a downstream protelomerase (TelT). We confirmed these contig ends as true termini maintained by TelT. The transposon preferentially targets linearized E. coli chromosome ends.

These elements, with a single transposon end and a telomere-defined opposite end, act as mobile telomeres. Their lifestyle ensures host dependence and may facilitate conjugative transfer via TtrA-mediated telomere mobilization in Streptomyces, contributing to telomere turnover.

In eukaryotes, some transposons target telomeres; in Drosophila, they even replace them. Peters lab and Barabas group show that bacteria with linear genomes also harbor diverse telomeric transposons. https://t.co/QxXMlJaenE @JoePetersLab @BarabasGroup

Eukaryotes have linear DNA and their telomeres are hotspots for transposons. Many bacteria are also known to have linear genomes. We identified several families of independently evolved telomeric transposons. 1/7

Excited to share our recent findings on Tn7 and its fascinating targeting mechanism, now published in Molecular Cell! 🧬🔬Check it out

Disclaimer: Photo was digitally edited to include @PopoMicro and @MachadoChacon who couldn't make the photo shot

It was a pleasure working with @PopoMicro on this review of CRISPR-Cas associated transposons (CAST). Hopefully it gives a sense for the diversity of Tn7-like transposons and CRISPR systems that independently combined. https://t.co/Aq8lz2HG3O

Hats off to the brilliant minds at Feng lab and Gootenberg lab for their awe-inspiring research achievement! (What a competitive field, people always have manuscripts ready at about the same time) https://t.co/kmAqHcB8X3

@JoePetersLab We thank Dr. Pietrasiak for providing the strain used in this work from the Terrestrial Cyanobacterial Culture Collection (NuMex TCCC). The frozen cell mass sent by Dr. Pietrasiak was even alive! Tough dessert cyanobacteria! @DrylandAlgae

Our small discovery just got published 😇. Relatively few cyanobacterial genomes are home to most known families of CRISPR-Cas transposons (CAST). After a careful search, we found a new capture: type I-D CAST~ https://t.co/QyaBuNXGHb @JoePetersLab

@JoePetersLab

PI is bullied!

Peters lab having fun with snow ~~

@PopoMicro @JoePetersLab @ShreyaKrishnan3 @MarcinNowotny @kellogg_liz @Nancy_Craig777 @alba_guarne @PhoebeARice @BarabasGroup @Christinahong9 Look what I found! Compliments of the talented @christinerbeck

Happy CSHL transposable meeting! #cshlTE22 @shsternberg @JoePetersLab @ShreyaKrishnan3 @MarcinNowotny @kellogg_liz @Nancy_Craig777 @alba_guarne @PhoebeARice @BarabasGroup @Christinahong9 Dyda lab

CRISPR 2022~ Popo happy~