Loss of the RNA trimethylguanosine cap is compatible with nuclear accumulation of spliceosomal snRNAs but not pre-mRNA splicing or snRNA processing during animal development

Autoři: Lin Cheng aff001;  Yu Zhang aff003;  Yi Zhang aff005;  Tao Chen aff001;  Yong-Zhen Xu aff004;  Yikang S. Rong aff002
Působiště autorů: School of Life Sciences, Sun Yat-sen University, Guangzhou, China aff001;  Hengyang College of Medicine, University of South China, Hengyang, China aff002;  Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China aff003;  College of Life Sciences, Wuhan University, Wuhan, China aff004;  Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, Bethesda, United States of America aff005
Vyšlo v časopise: Loss of the RNA trimethylguanosine cap is compatible with nuclear accumulation of spliceosomal snRNAs but not pre-mRNA splicing or snRNA processing during animal development. PLoS Genet 16(10): e32767. doi:10.1371/journal.pgen.1009098
Kategorie: Research Article
doi: 10.1371/journal.pgen.1009098


The 2,2,7-trimethylguanosine (TMG) cap is one of the first identified modifications on eukaryotic RNAs. TMG, synthesized by the conserved Tgs1 enzyme, is abundantly present on snRNAs essential for pre-mRNA splicing. Results from ex vivo experiments in vertebrate cells suggested that TMG ensures nuclear localization of snRNAs. Functional studies of TMG using tgs1 mutations in unicellular organisms yield results inconsistent with TMG being indispensable for either nuclear import or splicing. Utilizing a hypomorphic tgs1 mutation in Drosophila, we show that TMG reduction impairs germline development by disrupting the processing, particularly of introns with smaller sizes and weaker splice sites. Unexpectedly, loss of TMG does not disrupt snRNAs localization to the nucleus, disputing an essential role of TMG in snRNA transport. Tgs1 loss also leads to defective 3’ processing of snRNAs. Remarkably, stronger tgs1 mutations cause lethality without severely disrupting splicing, likely due to the preponderance of TMG-capped snRNPs. Tgs1, a predominantly nucleolar protein in Drosophila, likely carries out splicing-independent functions indispensable for animal development. Taken together, our results suggest that nuclear import is not a conserved function of TMG. As a distinctive structure on RNA, particularly non-coding RNA, we suggest that TMG prevents spurious interactions detrimental to the function of RNAs that it modifies.

Klíčová slova:

Drosophila melanogaster – Immunostaining – Introns – Larvae – Reverse transcriptase-polymerase chain reaction – RNA sequencing – Small nuclear RNA – Small nucleolar RNA


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