SPLICING OF MRNA PRECURSORS

Summary

Principal Investigator: Michael R Green
Abstract: DESCRIPTION (provided by applicant): The primary transcripts of most eukaryotic genes (precursor mRNAs;pre-mRNAs) contain intervening sequences (introns) that are removed by RNA splicing in a two-step pathway. Pre- mRNA splicing occurs in a ribonucleoprotein (RNP) complex called the spliceosome, which is composed of a large number of proteins and multiple U small nuclear RNP particles (U snRNPs). A small subset of introns, called U12-type introns (as opposed to the major class of U2-type introns), are spliced through the conventional two-step pathway but by a different spliceosome. The U2 snRNP Auxiliary Factor (U2AF) is an essential splicing factor, originally identified in our laboratory, that binds to the polypyrimidine (Py)-tract/3'splice site and initiates spliceosome assembly. Several human proteins are related to the small U2AF subunit, U2AF35, including a protein called U2AF35-related protein (Urp). During the past period of funding, we have shown that Urp is required for splicing of U12-type introns, and for the second step of U2- type intron splicing. In both cases, Urp directly contacts the 3'splice site. Using a combination of molecular biological, biochemical and structural approaches, we will continue to study how U2AF and Urp promote splicing. hUAP56, a member of the DExD/H-box family of RNA- dependent ATPases, was originally identified in our laboratory based upon its interaction with the large U2AF subunit (U2AF65). During the past period of funding we have shown that hUAP56 has multiple roles in U2-type splicing complex assembly, including disrupting the U2AF65-branchpoint/Py-tract interaction, interacting with U4 and U6 snRNAs, and unwinding of the U4/U6 snRNA duplex. We have also found that hUAP56 is required for splicing of U12-type introns. Experiments are proposed to understand the detailed mechanism by which hUAP56 facilitates diverse steps in splicing of U2- and U12-type introns. A variety of mammalian protein splicing factors contain an arginine-serine rich (RS) domain required to promote splicing. We have shown that direct contact with the branchpoint and 5'splice site is a general mechanism by which RS domains promote spliceosome assembly and splicing. Our studies have revealed a pathway of sequential interactions between RS domains and splicing signals during mammalian spliceosome assembly. Molecular, biochemical and structural experiments are proposed to understand in greater detail how RS domains are directed to splicing signals and promote spliceosome assembly and splicing, with an emphasis on studying the role of RS domain phosphorylation. Alternative splicing is an important mechanism of gene regulation and is responsible for substantially increasing diversity of the human proteome. However, the mechanisms that regulate alternative splicing remain largely unknown. During the past period of funding we have shown that FRG1, a protein whose over-expression is responsible for facioscapulohumeral muscular dystrophy (FSHD), functions by misregulating alternative splicing. Experiments are proposed to study how FRG1 affects splicing. In addition, we will perform genome-wide loss-of-function RNA interference screens to study mechanisms of splicing repression and to identify new splicing repressors. PUBLIC HEALTH RELEVANCE: Pre-mRNA splicing is an essential step for expression of the vast majority of protein coding genes in higher eukaryotes. Disruption of normal pre-mRNA splicinggdue to mutations in either the cis-acting regulatory sequences required for splicing or the trans- acting components of the splicing machineryghas been shown to result in a variety of human diseases including atypical cystic fibrosis, retinitis pigmentosa, spinal muscular atrophy and facioscapulohumeral muscular dystrophy, and has also been associated with cancer and metastasis. The experiments proposed in this application will increase our understanding of the factors and mechanisms involved in splice-site recognition, splicing complex assembly and splicing regulation, which may lead to the identification of new therapeutic targets and strategies for the treatment of diseases caused by aberrant pre-mRNA splicing. )
Funding Period: 1990-07-01 - 2015-03-31
more information: NIH RePORT

Top Publications

  1. pmc Structural basis for polypyrimidine tract recognition by the essential pre-mRNA splicing factor U2AF65
    E Allen Sickmier
    Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
    Mol Cell 23:49-59. 2006
  2. pmc Solution conformation and thermodynamic characteristics of RNA binding by the splicing factor U2AF65
    Jermaine L Jenkins
    Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
    J Biol Chem 283:33641-9. 2008
  3. pmc The U2AF35-related protein Urp contacts the 3' splice site to promote U12-type intron splicing and the second step of U2-type intron splicing
    Haihong Shen
    Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500 712, Korea
    Genes Dev 24:2389-94. 2010
  4. pmc Structure of phosphorylated SF1 bound to U2AF⁶⁵ in an essential splicing factor complex
    Wenhua Wang
    Center for RNA Biology and Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
    Structure 21:197-208. 2013
  5. pmc U2AF65 adapts to diverse pre-mRNA splice sites through conformational selection of specific and promiscuous RNA recognition motifs
    Jermaine L Jenkins
    Center for RNA Biology and Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
    Nucleic Acids Res 41:3859-73. 2013

Research Grants

Detail Information

Publications6

  1. pmc Structural basis for polypyrimidine tract recognition by the essential pre-mRNA splicing factor U2AF65
    E Allen Sickmier
    Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
    Mol Cell 23:49-59. 2006
    ..The energetic importance of conserved residues for Py tract binding is established by analysis of site-directed mutant U2AF(65) proteins using surface plasmon resonance...
  2. pmc Solution conformation and thermodynamic characteristics of RNA binding by the splicing factor U2AF65
    Jermaine L Jenkins
    Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
    J Biol Chem 283:33641-9. 2008
    ..Results of these studies suggest inter-RRM conformational plasticity as a possible means for U2AF65 to universally identify diverse pre-mRNA splice sites...
  3. pmc The U2AF35-related protein Urp contacts the 3' splice site to promote U12-type intron splicing and the second step of U2-type intron splicing
    Haihong Shen
    Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500 712, Korea
    Genes Dev 24:2389-94. 2010
    ..Thus, through recognition of a common splicing element, Urp facilitates distinct steps of U2- and U12-type intron splicing...
  4. pmc Structure of phosphorylated SF1 bound to U2AF⁶⁵ in an essential splicing factor complex
    Wenhua Wang
    Center for RNA Biology and Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
    Structure 21:197-208. 2013
    ..We further determine that SPSP phosphorylation and the SF1/U2AF⁶⁵ interface are essential in vivo. These results offer a structural prototype for phosphorylation-dependent control of pre-mRNA splicing factors...
  5. pmc U2AF65 adapts to diverse pre-mRNA splice sites through conformational selection of specific and promiscuous RNA recognition motifs
    Jermaine L Jenkins
    Center for RNA Biology and Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
    Nucleic Acids Res 41:3859-73. 2013
    ..Our results highlight both local and global conformational selection as a means for universal 3' splice site recognition by U2AF(65)...

Research Grants30

  1. Pre-mRNA Splicing Mechanisms
    Melissa J Moore; Fiscal Year: 2013
    ..Only by gaining a better understanding the cellular machinery mediating this process will we ultimately be able to treat such splicing-related diseases. ) ..
  2. Spliceosome Mechanism Dissected at the Single Molecule Level
    Nils G Walter; Fiscal Year: 2013
    ..Taken together, these advances will pave the way for, over the funding period, extensive mechanistic studies of yeast splicing and for studying alternative splicing in humans in the longer term. ..
  3. Mechanistic consequences of mutations in spliceosomal snRNAs
    Richard A Padgett; Fiscal Year: 2013
    ..Successful completion of these studies will advance our understanding of spliceosomal splicing, define the molecular causes of a human disease and determine the role of U12-dependent splicing in gene expression and development. ..
  4. SMN Control of snRNP Biogenesis: Role in RNA Splicing and Motor Neuron Survival
    Livio Pellizzoni; Fiscal Year: 2013
    ..These studies should provide insights into the basic mechanisms of RNA regulation and the molecular defects underlying SMA pathogenesis with the potential of identifying new candidate targets for therapeutic development. ..