Albany 2015:Book of Abstracts
June 9-13 2015
©Adenine Press (2012)
Shaping CRISPR repeat RNA for Cleavage by Cas6 endoribonucleases
Cellular RNAs are processed by endoribonucleases that often recognize distinct sequence or secondary structures within the RNA. A subclass of recently discovered CRISPR repeat RNA in bacteria contain minimally recognizable structural features that facilitate an unknown mechanism of recognition and processing by the Cas6 family of endoribonucleases. Crystal structures of two different Cas6 bound with their respective RNA substrate anologs are obtained and analyzed. While the RNA substrates in both cases have no stable secondary structures in solution, they are shaped by the endoribonucleases into a minimal stem loop structure immediately before their cleavage sites. The short stem loop facilitates the formation of the in line conformation of the scissile phosphate group necessary for cleavage. The endoribonucleases employ a variety of strategies to maintain the correct stem-loop structure in RNA that include multimerization, concurrent binding of minor recognition site, and base-pair mimicking. Our results demonstrate the extraordinary ability of proteins in recognizing structurally flexible RNA.
This research has been supported by NIH R01 GM099604.
Y. Shao, and H. Li, (2013) Recognition and Cleavage of a Nonstructured CRISPR RNA by Its Processing Endoribonuclease Cas6. Structure 21(3):385-93.
R. Wang, H. Zheng, G. Preamplume, Y. Shao, H. Li (2012) The impact of CRISPR repeat sequence on structures of a Cas6 protein-RNA complex. Protein Sci. 21(3):405-417.
R. Wang, G. Preamplume, M.P. Terns, R. M. Terns, & H. Li (2011) Interaction of the Cas6 riboendonuclease with CRISPR RNAs: recognition and cleavage. Structure 19(2):257
1 Institute of Molecular Biophysics, 2 Department of Chemistry and Biochemistry