Degradation of SERRATE via ubiquitin-independent 20S proteasome to survey RNA metabolism

Abstract

Serrate (SE) is a key factor in RNA metabolism. Here, we report that SE binds 20S core proteasome α subunit G1 (PAG1) among other components and is accumulated in their mutants. Purified PAG1-containing 20S proteasome degrades recombinant SE via an ATP- and ubiquitin-independent manner in vitro. Notwithstanding, PAG1 is a positive regulator for SE in vivo as pag1 shows comparable molecular and /or developmental defects relative to se . Furthermore, SE is poorly assembled into macromolecular complexes exemplified by microprocessor in pag1 compared to Col-0. Intriguingly, SE overexpression triggered destruction of both transgenic and endogenous protein, leading to similar phenotypes of se and SE overexpression lines. Thus, we propose that PAG1 degrades intrinsically disordered portion of SE to secure functionality of folded SE that is assembled and protected in macromolecular complexes. This study provides new insight into how 20S proteasome regulates RNA metabolism through controlling its key factor in eukaryotes.

HYL1-CLEAVAGE SUBTILASE 1 (HCS1) suppresses miRNA biogenesis in response to light-to-dark transition

“…Moreover, we suggested that DCL1 can be degraded by an unknown protease during skotomorphogenesis and light/dark conversion ( 38 ). Furthermore, damaged SE is degraded by ubiquitin-independent proteasomal activity ( 39 ). Intriguingly, a recent study suggested that Dicer is cleaved by an unknown serine protease in undifferentiated monocytes ( 40 , 41 ).…”

The epigenetic factor FVE orchestrates cytoplasmic SGS3-DRB4-DCL4 activities to promote transgene silencing in Arabidopsis

“…The interaction between FVE and DRB4 was further confirmed by the Co-IP assay with protein extracts from transfected N. benthamiana leaves ( Fig. 9B ) ( 39 ). Y2H and LCI assays for SGS3 and DRB4 also detected their interaction in vivo ( Fig.…”

“… ( A ) LCI assay showed that FVE (top) and FVE-8 (bottom) interact with DRB4 in N. benthamiana . PAG1-nLUC/cLUC-SE is a positive control ( 39 ). See also fig.…”

“…Leaves of 4-week-old plants of Col-0, E5-4, fve-8 , and fve-8; gFVE were used as resources of protoplasts. Eighteen hours after transfection, fluorescence signals in the protoplast were visualized by a Leica SP8 confocal microscope ( 39 ). Samples were excited by a 514-nm argon laser with an emission of 527 nm for YFP and 633 nm for chlorophyll autofluorescence, respectively.…”

DEAD-box helicases modulate dicing body formation in Arabidopsis

“…S5G). A recent study showed that SE contains an intrinsically unfolded region and undergoes degradation via the 20 S proteasome to secure the functionality of folded and functional SE ( 20 ). Hence, we suspected that RH6, RH8, and RH12 may facilitate the phase separation of SE during D-body assembly.…”