How splicing factors are recruited to nascent transcripts in the nucleus in order to assemble spliceosomes on newly synthesised pre-mRNAs is unknown. To address this question, we compared the intranuclear trafficking kinetics of small nuclear ribonucleoprotein particles (snRNP) and non-snRNP proteins in the presence and absence of splicing activity. Photobleaching experiments clearly show that spliceosomal proteins move continuously throughout the entire nucleus independently of ongoing transcription or splicing. Using quantitative experimental data, a mathematical model was applied for spliceosome assembly and recycling in the nucleus. The model assumes that splicing proteins move by Brownian diffusion and interact stochastically with binding sites located at different subnuclear compartments. Inhibition of splicing, which reduces the number of pre-mRNA binding sites available for spliceosome assembly, was modeled as a decrease in the on-rate binding constant in the nucleoplasm. Simulation of microscopy experiments before and after splicing inhibition yielded results consistent with the experimental observations. Taken together, our data argue against the view that spliceosomal components are stored in nuclear speckles until a signal triggers their recruitment to nascent transcripts. Rather, the results suggest that splicing proteins are constantly diffusing throughout the entire nucleus and collide randomly and transiently with pre-mRNAs.
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http://dx.doi.org/10.1371/journal.pcbi.0030201 | DOI Listing |
Biochim Biophys Acta Gen Subj
January 2025
Computational Structural Biology Laboratory, Department of Bioscience and Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India; Bioinformatics Centre, Department of Bioscience and Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India. Electronic address:
Conformational switching in RNA binding proteins (RBPs) are crucial for regulation of RNA processing and transport. Dysregulation or mutations in RBPs and broad RNA processing abnormalities are related to many human diseases including neurodegenerative disorders. Here, we review the role of protein-RNA conformational switches in RBP-RNA complexes.
View Article and Find Full Text PDFZhong Nan Da Xue Xue Bao Yi Xue Ban
July 2024
Southern Hospital affiliated with Shenzhen University, Shenzhen Guangdong 518001, China.
Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype with poor prognosis. RNA alternative splicing dysregulation plays a critical role in the initiation and progression of TNBC. This article systematically introduces the basic process of RNA splicing and then focuses on reviewing the aberrant alternative splicing events and their biological effects in TNBC: 1) Multiple splicing-related factors promote tumor cell proliferation and mediate chemotherapy resistance by regulating the alternative splicing of genes involved in cell survival and drug response; 2) dysregulation of splicing regulatory networks leads to altered splicing of multiple metastasis-related genes, promoting tumor invasion and metastasis; 3) aberrant alternative splicing events participate in tumor progression by affecting the expression of DNA damage repair genes; 4) dysregulation of alternative splicing is also involved in the regulation of tumor immune evasion and stem cell properties.
View Article and Find Full Text PDFRNA
January 2025
University of Helsinki, Institute of Biotechnology
Minor spliceosome is responsible for recognizing and excising a specific subset of divergent introns during the pre-mRNA splicing process. Mutations in the unique snRNA and protein components of the minor spliceosome are increasingly being associated with a variety of germline and somatic human disorders, collectively termed as minor spliceosomopathies. Understanding the mechanistic basis of these diseases has been challenging due to limited functional information on many minor spliceosome components.
View Article and Find Full Text PDFNat Commun
January 2025
Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
The assembly of repressive heterochromatin in eukaryotic genomes is crucial for silencing lineage-inappropriate genes and repetitive DNA elements. Paradoxically, transcription of repetitive elements within constitutive heterochromatin domains is required for RNA-based mechanisms, such as the RNAi pathway, to target heterochromatin assembly proteins. However, the mechanism by which heterochromatic repeats are transcribed has been unclear.
View Article and Find Full Text PDFJ Biol Chem
December 2024
Department of Molecular Cell and Developmental Biology, University of California, Santa Cruz, California, USA; Center for Molecular Biology of RNA, University of California, Santa Cruz, California, USA. Electronic address:
The spliceosome protein, SF3B1 associates with U2 snRNP during early spliceosome assembly for pre-mRNA splicing. Frequent somatic mutations in SF3B1 observed in cancer necessitates characterization of its role in identifying the branchpoint adenosine of introns. Remarkably, SF3B1 is the target of three distinct natural product drugs, each identified by their potent anti-tumor properties.
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