NIEUWE CRISPR PUBLICATIE IN MOLECULAR CELL

Nieuwe publicatie in Molecular Cell, maar het is ook nog even wachten op de printverversie van het Amerikaanse blad. Want, als alles gaat zoals het is beloofd, staat de door ded ontworpen cover op de editie van 20 november. Tot dan maar even geduld hebben.
Voor een eerste blik op het artikel (met een korte samenvatting in het Engels), zie de online versie van 6 november 2014; klik ook op :
publicatie in Mol Cell

Highlights

• •TtCsm and TtCmr complexes share similar crRNA guides
• •Architecture of TtCsm resembles that of Type I and Type III-B complexes
• •TtCsm degrades target RNA in a stepwise fashion, analogous to Cmr complex
• •TtCsm crRNA guides appear to lack a Type I-like seed sequence

Summary

CRISPR-Cas is a prokaryotic adaptive immune system that provides sequence-specific defense against foreign nucleic acids. Here we report the structure and function of the effector complex of the Type III-A CRISPR-Cas system of Thermus thermophilus: the Csm complex (TtCsm). TtCsm is composed of five different protein subunits (Csm1–Csm5) with an uneven stoichiometry and a single crRNA of variable size (35–53 nt). The TtCsm crRNA content is similar to the Type III-B Cmr complex, indicating that crRNAs are shared among different subtypes. A negative stain EM structure of the TtCsm complex exhibits the characteristic architecture of Type I and Type III CRISPR-associated ribonucleoprotein complexes. crRNA-protein crosslinking studies show extensive contacts between the Csm3 backbone and the bound crRNA. We show that, like TtCmr, TtCsm cleaves complementary target RNAs at multiple sites. Unlike Type I complexes, interference by TtCsm does not proceed via initial base pairing by a seed sequence.