Structure of the dual enzyme Ire1 reveals the basis for catalysis and regulation in nonconventional RNA splicing.
Ire1 is an ancient transmembrane sensor of ER stress with dual protein kinase and ribonuclease activities. In response to ER stress, Ire1 catalyzes the splicing of target mRNAs in a spliceosome-independent manner. We have determined the crystal structure of the dual catalytic region of Ire1at 2.4 A resolution, revealing the fusion of a domain, which we term the KEN domain, to the protein kinase domain. Dimerization of the kinase domain composes a large catalytic surface on the KEN domain which carries out ribonuclease function. We further show that signal induced trans-autophosphorylation of the kinase domain permits unfettered binding of nucleotide, which in turn promotes dimerization to compose the ribonuclease active site. Comparison of Ire1 to a topologically disparate ribonuclease reveals the convergent evolution of their catalytic mechanism. These findings provide a basis for understanding the mechanism of action of RNaseL and other pseudokinases, which represent 10% of the human kinome.
Lee
Kenneth P K
KP
Program in Systems Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada.
Dey
Madhusudan
M
Neculai
Dante
D
Cao
Chune
C
Dever
Thomas E
TE
Sicheri
Frank
F
D017398:Alternative Splicing / Q000235:genetics*; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000502:physiology; D020134:Catalytic Domain / Q000502:physiology; D018360:Crystallography, X-Ray; D019281:Dimerization; D004721:Endoplasmic Reticulum / Q000378:metabolism; D019143:Evolution, Molecular; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D010766:Phosphorylation; D010770:Phosphotransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D011487:Protein Conformation; D017510:Protein Folding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012260:Ribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015003:Yeasts / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D008562:Membrane Glycoproteins; D009711:Nucleotides; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D010770:Phosphotransferases; C082863:IRE1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D012260:Ribonucleases