Multiple forms of the U2 small nuclear ribonucleoprotein auxiliary factor U2AF subunits expressed in higher plants.
نویسندگان
چکیده
Requirements for intron recognition during pre-mRNA splicing in plants differ from those in vertebrates and yeast. Plant introns contain neither conserved branch points nor distinct 3' splice site-proximal polypyrimidine tracts characteristic of the yeast and vertebrate introns, respectively. However, they are strongly enriched in U residues throughout the intron, property essential for splicing. To understand the roles of different sequence elements in splicing, we are characterizing proteins involved in intron recognition in plants. In this work we show that Nicotiana plumbaginifolia, a dicotyledonous plant, contains two genes encoding different homologs of the large 50-65-kDa subunit of the polypyrimidine tract binding factor U2AF, characterized previously in animals and Schizosaccharomyces pombe. Both plant U2AF65 isoforms, referred to as NpU2AF65a and NpU2AF65b, support splicing of an adenovirus pre-mRNA in HeLa cell nuclear extracts depleted of the endogenous U2AF factor. Both proteins interact with RNA fragments containing plant introns and show affinity for poly(U) and, to a lesser extend, poly(C) and poly(G). The branch point or the 3' splice site regions do not contribute significantly to intron recognition by NpU2AF65. The existence of multiple isoforms of U2AF may be quite general in plants because two genes expressing U2AF65 have been identified in Arabidopsis, and different isoforms of the U2AF small subunit are expressed in rice.
منابع مشابه
Molecular Characterization and Phylogeny of U2AF Homologs in Plants
U2AF (U2 small nuclear ribonucleoprotein auxiliary factor) is an essential splicing factor with critical roles in recognition of the 3#-splice site. In animals, the U2AF small subunit (U2AF) can bind to the 3#-AG intron border and promote U2 small nuclear RNP binding to the branch-point sequences of introns through interaction with the U2AF large subunit. Two copies of U2AFencoding genes were i...
متن کاملCloning and intracellular localization of the U2 small nuclear ribonucleoprotein auxiliary factor small subunit.
U2 small nuclear ribonucleoprotein auxiliary factor (U2AF), an essential mammalian splicing factor, is composed of two subunits: a 65-kDa protein (U2AF65), which binds the pre-mRNA polypyrimidine tract and is required for in vitro splicing, and an associated 35-kDa protein (U2AF35). Here we report the isolation of a cDNA encoding U2AF35. U2AF35 contains sequence motifs found in several mammalia...
متن کاملMolecular characterization and phylogeny of U2AF35 homologs in plants.
U2AF (U2 small nuclear ribonucleoprotein auxiliary factor) is an essential splicing factor with critical roles in recognition of the 3'-splice site. In animals, the U2AF small subunit (U2AF35) can bind to the 3'-AG intron border and promote U2 small nuclear RNP binding to the branch-point sequences of introns through interaction with the U2AF large subunit. Two copies of U2AF35-encoding genes w...
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The U2 snRNP auxiliary factor (U2AF) is an essential splicing factor composed of two subunits, a large, 65-kDa subunit (U2AF(65)) and a small subunit, U2AF(35). U2AF(65) binds to the polypyrimidine tract upstream from the 3' splice site and promotes U2 snRNP binding to the pre-mRNA. Based on in vitro studies, it has been proposed that U2AF(35) plays a role in assisting U2AF(65) recruitment to n...
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The pre-mRNA splicing factor U2AF (U2 snRNP auxiliary factor) has an essential role in 3' splice site selection. U2AF binds the intron pyrimidine tract between the branchpoint and the 3' splice site and recruits U2 snRNP to the branch site at an early step in spliceosome assembly. Human U2AF is a heterodimer composed of large (hU2AF65) and small (hU2AF35) subunits. Both subunits contain a domai...
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 273 51 شماره
صفحات -
تاریخ انتشار 1998