Drosha promotes splicing of a pre-microRNA-like alternative exon.
The ribonuclease III enzyme Drosha has a central role in the biogenesis of microRNA (miRNA) by binding and cleaving hairpin structures in primary RNA transcripts into precursor miRNAs (pre-miRNAs). Many miRNA genes are located within protein-coding host genes and cleaved by Drosha in a manner that is coincident with splicing of introns by the spliceosome. The close proximity of splicing and pre-miRNA biogenesis suggests a potential for co-regulation of miRNA and host gene expression, though this relationship is not completely understood. Here, we describe a cleavage-independent role for Drosha in the splicing of an exon that has a predicted hairpin structure resembling a Drosha substrate. We find that Drosha can cleave the alternatively spliced exon 5 of the eIF4H gene into a pre-miRNA both in vitro and in cells. However, the primary role of Drosha in eIF4H gene expression is to promote the splicing of exon 5. Drosha binds to the exon and enhances splicing in a manner that depends on RNA structure but not on cleavage by Drosha. We conclude that Drosha can function like a splicing enhancer and promote exon inclusion. Our results reveal a new mechanism of alternative splicing regulation involving a cleavage-independent role for Drosha in splicing.
Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America; School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
Mallory A
MA
Havens
Department of Biology, Lake Forest College, Lake Forest, Illinois, United States of America.
Ashley A
AA
Reich
Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America; School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
Michelle L
ML
Hastings
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D039642:Eukaryotic Initiation Factors / Q000235:genetics; D005091:Exons; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D012322:RNA Precursors / Q000235:genetics*; D043244:Ribonuclease III / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid
C111495:EIF4H protein, human; D039642:Eukaryotic Initiation Factors; D035683:MicroRNAs; D012322:RNA Precursors; C517918:DROSHA protein, human; D043244:Ribonuclease III