Lariat debranching by RNA DEBRANCHING ENZYME 1 depends on SICKLE inArabidopsis thaliana

Abstract

ABSTRACTSpliceosome mediated intron removal from precursor mRNAs (pre-mRNAs) generates circular RNAs called intron lariats. RNA DEBRANCHING ENZYME 1 (DBR1) ribonucleases linearize, or debranch, intron lariats to allow their degradation.DBR1genes occur across eukaryotes and are essential in animals and plants. High levels of intron lariats in the weakArabidopsis thaliana dbr1-2allele inhibits primary microRNA (pri-miRNA) processing, disrupting miRNA production and miRNA-regulated growth and development. Arabidopsissickle(sic) mutants alter pri-miRNA processing and pre-mRNA splicing. This study demonstratessicmutants accumulate intron lariats matching those in weakdbralleles. The strongsic-1and weakdbr1-3alleles together cause synthetic lethality, while weaksic-3withdbr1-3has intron lariat accumulation likesic-3. Further,sic-3,dbr1-3, andsic-3 dbr1-3similarly alter circadian rhythms and growth of roots and rosettes. The conserved MPLKIP amino acid motif in SIC mediates physical interaction with DBR1in vitroand is required for intron lariat debranchingin vivo. Thus, MPLKIP containing proteins, like SIC and human TTDN1, act with cognate DBR1 proteins to maintain RNA homeostasis critical for growth and development.