title: Structure of a group II intron in complex with its reverse transcriptase.
abstract: Bacterial group II introns are large catalytic RNAs related to nuclear spliceosomal introns and eukaryotic retrotransposons. They self-splice, yielding mature RNA, and integrate into DNA as retroelements. A fully active group II intron forms a ribonucleoprotein complex comprising the intron ribozyme and an intron-encoded protein that performs multiple activities including reverse transcription, in which intron RNA is copied into the DNA target. Here we report cryo-EM structures of an endogenously spliced Lactococcus lactis group IIA intron in its ribonucleoprotein complex form at 3.8-Å resolution and in its protein-depleted form at 4.5-Å resolution, revealing functional coordination of the intron RNA with the protein. Remarkably, the protein structure reveals a close relationship between the reverse transcriptase catalytic domain and telomerase, whereas the active splicing center resembles the spliceosomal Prp8 protein. These extraordinary similarities hint at intricate ancestral relationships and provide new insights into splicing and retromobility.
authors.affiliation: Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, USA.
authors.forename: Guosheng
authors.initials: G
authors.lastname: Qu
authors.affiliation: Laboratory of Cellular and Molecular Basis of Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA.
authors.forename: Prem Singh
authors.initials: PS
authors.lastname: Kaushal
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA.
authors.forename: Hideki
authors.initials: H
authors.lastname: Shigematsu
authors.affiliation: Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, USA.
authors.forename: Carol Lyn
authors.initials: CL
authors.lastname: Piazza
authors.affiliation: Laboratory of Cellular and Molecular Basis of Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA.|Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, USA.
authors.forename: Rajendra Kumar
authors.initials: RK
authors.lastname: Agrawal
authors.affiliation: Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, USA.|Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, USA.
authors.forename: Marlene
authors.initials: M
authors.lastname: Belfort
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.|Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA.
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D013294:Lactococcus lactis / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D016337:RNA, Catalytic / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D012194:RNA-Directed DNA Polymerase / Q000737:chemistry / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D016337:RNA, Catalytic; D012261:Ribonucleoproteins; C099785:LtrA protein, Lactococcus lactis; D012194:RNA-Directed DNA Polymerase