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. Nevertheless, 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 the microprocessor in pag1 compared with Col-0. SE overexpression triggered the destruction of both transgenic and endogenous protein, leading to similar phenotypes of se and SE overexpression lines. We therefore propose that PAG1 degrades the intrinsically disordered portion of SE to secure the functionality of folded SE that is assembled and protected in macromolecular complexes. This study provides insight into how the 20S proteasome regulates RNA metabolism through controlling its key factor in eukaryotes.

SERRATE（SE）是RNA代谢的关键因素。在这里，我们报道SE与其他成分结合20S核心蛋白酶体α亚基G1（PAG1），并在其突变体中积累。纯化的含PAG1的20S蛋白酶体在体外通过ATP和泛素非依赖性方式降解重组SE。然而，PAG1是体内SE的阳性调节剂，因为pag1显示出与se相当的分子和/或发育缺陷。此外，SE组装不良的大分子复合物，与Col-0相比，在pag1中的微处理器中得到了例证。SE的过表达引发转基因和内源蛋白的破坏，导致类似的表型se和SE过表达线。因此，我们建议PAG1降解SE的固有无序部分，以确保在高分子复合物中组装并受保护的折叠SE的功能。这项研究提供了关于20S蛋白酶体如何通过控制其在真核生物中的关键因子来调节RNA代谢的见解。