Project description:A battery of spliceosome-associated proteins has been identified in microRNA (miRNA) biogenesis; however, the underlying mechanisms remain elusive. The intron lariat spliceosome (ILS) complex is highly conserved among eukaryotes and its disassembly marks the end of a canonical splicing cycle. In this study, we show that two conserved disassembly factors of the ILS complex, ILP1 and NTR1, positively regulate microRNA biogenesis through facilitating transcriptional elongation in Arabidopsis. ILP1 and NTR1 form a stable complex and co-regulate alternative splicing of more than a hundred genes across the genome including the core circadian gene LHY and some pri-miRNAs. Dysfunction in either ILP1 or NTR1 result in reduced RNA polymerase II occupancy at elongated regions of MIR chromatins, without affecting MIR promoter activity, pri-miRNA decay and DCL1 processing. Our results provide insights into the molecular mechanisms of spliceosomal machineries in non-coding RNA regulation.
Project description:The evolutionarily conserved, putative RNA helicase MAC7 exists in both animals and plants. The human MAC7 homolog, Aquarius, is part of the spliceosome and plays a role in pre-mRNA splicing in vitro. In Arabidopsis, MAC7 was shown to be part of the MOS4-associated complex (MAC), which is required for plant defense and development. Here through RNA-seq analysis we discover that down-regulated genes in MAC subunit mutants are mostly involved in plant defense and stimulus response, confirming a role of MAC in the regulation of biotic and abiotic stress responses. We also discover global intron retention defects in mutants in three members of MAC, thus linking the functions of MAC to splicing in Arabidopsis. In addition, we show that mac7-1, a partial loss-of-function mutant in MAC7, and two other MAC subunit mutants, mac3a mac3b and prl1 prl2, exhibit reduced microRNA levels in general, indicating that MAC promotes microRNA biogenesis. The mac7-1 mutant shows reduced primary miRNA (pri-miRNA) levels without affecting MIR promoter activity or the degradation of pri-miRNA transcripts, implicating functions of MAC7 during transcription elongation or maturation of pri-miRNAs. As a nuclear protein, MAC7 is not localized in dicing bodies, but it affects the localization of HYL1 to dicing bodies. We propose that MAC acts to link MIR transcription to pri-miRNA processing.
Project description:The evolutionarily conserved, putative RNA helicase MAC7 exists in both animals and plants. The human MAC7 homolog, Aquarius, is part of the spliceosome and plays a role in pre-mRNA splicing in vitro. In Arabidopsis, MAC7 was shown to be part of the MOS4-associated complex (MAC), which is required for plant defense and development. Here through RNA-seq analysis we discover that down-regulated genes in MAC subunit mutants are mostly involved in plant defense and stimulus response, confirming a role of MAC in the regulation of biotic and abiotic stress responses. We also discover global intron retention defects in mutants in three members of MAC, thus linking the functions of MAC to splicing in Arabidopsis. In addition, we show that mac7-1, a partial loss-of-function mutant in MAC7, and two other MAC subunit mutants, mac3a mac3b and prl1 prl2, exhibit reduced microRNA levels in general, indicating that MAC promotes microRNA biogenesis. The mac7-1 mutant shows reduced primary miRNA (pri-miRNA) levels without affecting MIR promoter activity or the degradation of pri-miRNA transcripts, implicating functions of MAC7 during transcription elongation or maturation of pri-miRNAs. As a nuclear protein, MAC7 is not localized in dicing bodies, but it affects the localization of HYL1 to dicing bodies. We propose that MAC acts to link MIR transcription to pri-miRNA processing.
Project description:Alternative splicing plays a major role in expanding the potential informational content of eukaryotic genomes. It is an important post-transcriptional regulatory mechanism that can increase protein diversity and affect mRNA stability. Cold stress, which adversely affects plants growth and development, regulates the transcription and splicing of plants splicing factors. This affects the pre-mRNA processing of many genes. To identify cold regulated alternative splicing we applied Affymetrix Arabidopsis tiling arrays to survey the transcriptome under cold treatment conditions.