![]() Following transcription, pre-snRNAs are subjected to endonucleolytic cleavage at specific sites to remove the RNA fragment transcribed beyond the 3′-end of mature snRNAs. In Arabidopsis ( Arabidopsis thaliana), the DNA-dependent RNA polymerase II (Pol II) synthesizes the primary snRNA transcripts (pre-snRNAs) U1, U2, U4, U5, and U12, but not U6, which is transcribed by Pol III ( Carbon et al., 1987 Vankan and Filipowicz, 1988). Their biogenesis involves transcription and subsequent processing steps. Small nuclear RNAs (snRNAs Hadjiolov et al., 1966), a class of noncoding RNAs, are the basal components of the spliceosome and play essential roles in pre-mRNA splicing ( Black et al., 1985 Ray et al., 1997 Guo et al., 2009). Taken together, these data reveal that DSP1 and DSP4 function is essential for pollen development, and that the two cooperatively promote pre-snRNA transcription and 3′-end processing efficiency and accuracy. We also detected miscleaved pre-snRNAs in dsp1-1 dsp4-1, but not in dsp1-1 or dsp4-1. In addition, Pol II occupancy at snRNA loci is lower in dsp1-1 dsp4-1 than in either single mutant. ![]() Interestingly, dsp1-1 dsp4-1 double mutants exhibit complete male sterility and reduced pre-snRNA transcription and 3′-end maturation, unlike dsp1-1 or dsp4-1. Null dsp4-1 mutants have pleiotropic developmental defects, including impaired pollen development and reduced pre-snRNA transcription and 3′ maturation, resembling the phenotype of the dsp1-1 mutant. Here, we show that DSP4, a member of the metallo-β-lactamase family, physically interacts with DSP1 through its β-Casp domain. ![]() Yet it remains unclear how DSP1 complex subunits act together to process snRNAs. We have previously shown that the Arabidopsis ( Arabidopsis thaliana) Defective in snRNA Processing 1 (DSP1) complex, composed of at least five subunits, is responsible for snRNA 3′ maturation and is essential for plant development. Most snRNAs are transcribed by the DNA-dependent RNA polymerase II (Pol II) and require 3′-end endonucleolytic cleavage. Small nuclear RNAs (snRNAs) play essential roles in spliceosome assembly and splicing. ![]()
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