Biomaterial Database

Small nuclear ribonucleoprotein (RNP) U2 contains numerous additional proteins and has a bipartite RNP structure under splicing conditions. 1993

S E Behrens, and K Tyc, and B Kastner, and J Reichelt, and R Lührmann

Institut für Molekularbiologie und Tumorforschung, Philipps-Universität Marburg, Germany.

Small nuclear (sn) ribonucleoprotein (RNP) U2 functions in the splicing of mRNA by recognizing the branch site of the unspliced pre-mRNA. When HeLa nuclear splicing extracts are centrifuged on glycerol gradients, U2 snRNPs sediment at either 12S (under high salt concentration conditions) or 17S (under low salt concentration conditions). We isolated the 17S U2 snRNPs from splicing extracts under nondenaturing conditions by using centrifugation and immunoaffinity chromatography and examined their structure by electron microscope. In addition to common proteins B', B, D1, D2, D3, E, F, and G and U2-specific proteins A' and B", which are present in the 12S U2 snRNP, at least nine previously unidentified proteins with apparent molecular masses of 35, 53, 60, 66, 92, 110, 120, 150, and 160 kDa bound to the 17S U2 snRNP. The latter proteins dissociate from the U2 snRNP at salt concentrations above 200 mM, yielding the 12S U2 snRNP particle. Under the electron microscope, the 17S U2 snRNPs exhibited a bipartite appearance, with two main globular domains connected by a short filamentous structure that is sensitive to RNase. These findings suggest that the additional globular domain, which is absent from 12S U2 snRNPs, contains some of the 17S U2-specific proteins. The 5' end of the RNA in the U2 snRNP is more exposed for reaction with RNase H and with chemical probes when the U2 snRNP is in the 17S form than when it is in the 12S form. Removal of the 5' end of this RNA reduces the snRNP's Svedberg value from 17S to 12S. Along with the peculiar morphology of the 17S snRNP, these data indicate that most of the 17S U2-specific proteins are bound to the 5' half of the U2 snRNA.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D009690	Nucleic Acid Conformation	The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.	DNA Conformation,RNA Conformation,Conformation, DNA,Conformation, Nucleic Acid,Conformation, RNA,Conformations, DNA,Conformations, Nucleic Acid,Conformations, RNA,DNA Conformations,Nucleic Acid Conformations,RNA Conformations
D002458	Cell Fractionation	Techniques to partition various components of the cell into SUBCELLULAR FRACTIONS.	Cell Fractionations,Fractionation, Cell,Fractionations, Cell
D002467	Cell Nucleus	Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Cell Nuclei,Nuclei, Cell,Nucleus, Cell
D006367	HeLa Cells	The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for, among other things, VIRUS CULTIVATION and PRECLINICAL DRUG EVALUATION assays.	Cell, HeLa,Cells, HeLa,HeLa Cell
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006860	Hydrogen Bonding	A low-energy attractive force between hydrogen and another element. It plays a major role in determining the properties of water, proteins, and other compounds.	Hydrogen Bonds,Bond, Hydrogen,Hydrogen Bond
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA