α-Crystalline Domains and Intrinsically Disordered Regions Can Work in Parallel to Induce Accumulation of MBD6 at Chromocenters in Arabidopsis thaliana

TL;DR

This study shows that two protein regions, ACDs and IDRs, can work together to help MBD6 gather at specific DNA regions in Arabidopsis.

Contribution

The paper reveals that ACDs and IDRs can function in parallel to drive MBD6 accumulation at chromocenters.

Findings

ACDs and IDRs can both facilitate MBD6 accumulation at chromocenters in Arabidopsis.

IDRs fused to MBD6 can partially replace ACDs in gene-silencing functions.

ACD15 and ACD21 are still needed for full MBD6 accumulation when using IDRs.

Abstract

Proteins are localized and concentrated at cellular and genomic locations for specific and efficient functions. Efforts to understand protein accumulation in eukaryotic organisms have primarily focused on multivalent interactions between intrinsically disordered regions (IDRs) as mediators of protein condensation. We previously showed that α-crystalline domain (ACD) proteins 15 (ACD15) and 21 (ACD21) were required for multimerization and the accumulation of gene-silencing methyl-CpG-binding domain protein 6 (MBD6) at chromocenters in Arabidopsis thaliana. Here, we demonstrate that ACDs and IDRs can act as parallel mechanisms, facilitating higher-order MBD6 assemblies. Using human IDRs known to be important for protein accumulation, we replicated and enhanced the accumulation of MBD6 at chromocenters. In addition, IDRs fused to MBD6 could substitute for ACD function and partially reconstitute the MBD6 gene-silencing function. However, the accumulation of MBD6 by IDRs still required ACD15 and ACD21 for full effect. These results establish that ACD-mediated protein accumulation is a mechanism that can function similarly to and together with IDR-mediated mechanisms.

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