AUTHOR=Taylor Hannah N. , Laderman Eric , Armbrust Matt , Hallmark Thomson , Keiser Dylan , Bondy-Denomy Joseph , Jackson Ryan N. 

TITLE=Positioning Diverse Type IV Structures and Functions Within Class 1 CRISPR-Cas Systems

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.671522

DOI=10.3389/fmicb.2021.671522

ISSN=1664-302X

ABSTRACT=<p>Type IV CRISPR systems encode CRISPR associated (Cas)-like proteins that combine with small RNAs to form multi-subunit ribonucleoprotein complexes. However, the lack of Cas nucleases, integrases, and other genetic features commonly observed in most CRISPR systems has made it difficult to predict type IV mechanisms of action and biological function. Here we summarize recent bioinformatic and experimental advancements that collectively provide the first glimpses into the function of specific type IV subtypes. We also provide a bioinformatic and structural analysis of type IV-specific proteins within the context of multi-subunit (class 1) CRISPR systems, informing future studies aimed at elucidating the function of these cryptic systems.</p>