SUMOylation of GTF2IRD1 Regulates Protein Partner Interactions and Ubiquitin-Mediated Degradation

Abstract

GTF2IRD1 is one of the genes implicated in Williams-Beuren syndrome, a disease caused by haploinsufficiency of certain dosage-sensitive genes within a hemizygous microdeletion of chromosome 7. GTF2IRD1 is a prime candidate for some of the major features of the disease, presumably caused by abnormally reduced abundance of this putative transcriptional repressor protein. GTF2IRD1 has been shown to interact with the E3 SUMO ligase PIASxβ, but the significance of this relationship is largely unexplored. Here, we demonstrate that GTF2IRD1 can be SUMOylated by the SUMO E2 ligase UBC9 and the level of SUMOylation is enhanced by PIASxβ. A major SUMOylation site was mapped to lysine 495 within a conserved SUMO consensus motif. SUMOylation of GTF2IRD1 alters the affinity of the protein for binding partners that contain SUMO-interacting motifs, including a novel family member of the HDAC repressor complex, ZMYM5, and PIASxβ itself. In addition, we show that GTF2IRD1 is targeted for ubiquitination and proteasomal degradation. Cross regulation by SUMOylation modulates this process, thus potentially regulating the level of GTF2IRD1 protein in the cell. These findings, concerning post-translational control over the activity and stability of GTF2IRD1, together with previous work showing how GTF2IRD1 directly regulates its own transcription levels suggest an evolutionary requirement for fine control over GTF2IRD1 activity in the cell.

Nuclear translocation of IGF-1R via p150Glued and an importin-β/RanBP2-dependent pathway in cancer cells

“…Since these original studies, a vast variety of proteins have been identified to be SUMO targets. SUMOylation regulates protein stability [154], protein-protein interactions [155] and subcellular localization [156], thereby impacting nearly all processes in the cell. The SUMOylation process is energy dependent similar to the ubiquitination process and involves three classes of enzymes, E1, E2 and E3.…”

Functions of Gtf2i and Gtf2ird1 in the developing brain: transcription, DNA-binding, and long term behavioral consequences

“…This supports the role of GTF2IRD1 in regulating chromatin by transcriptionally controlling other chromatin modifiers. These data, along with the localization pattern of GTF2IRD1 in the nucleus and its direct association with other chromatin modifiers such as ZMYM5 (18, 39), suggests that GTF2IRD1 can exert its regulation of chromatin at several different levels of biological organization. Motif enrichment analysis of GTF2IRD1 peaks indicated that CTCF cobind with GTF2IRD1.…”

The nuclear localization pattern and interaction partners of GTF2IRD1 demonstrate a role in chromatin regulation

“…While some GTF2IRD1 protein binding partners have been reported (Tussie-Luna et al 2002;Widagdo et al 2012) this area is unexplored and we therefore set out to address this need using a comprehensive screening approach.…”

“…Five of these clones were not pursued beyond sequence identification as they were known to be solely cytoplasmic, extracellular or cell membrane localized and were less likely to be of biological relevance. Two of the proteins have been described previously as interacting nuclear partners (TussieLuna et al 2002;Widagdo et al 2012). Of the remaining 33 proteins, 26 either shuttle into the nucleus or are primarily located in the nucleus according to known functions or predictions summarized in the subcellular localization database, COMPARTMENTS (Binder et al 2014).…”

“…Location data are based on reported subcellular localizations or predicted/inferred information using COMPARTMENTS (Binder et al 2014). Several clones occurred in both screens (a) and 2 genes (b) have been described previously (Tussie-Luna et al 2002;Widagdo et al 2012). Some interactions were not pursued beyond sequence analysis (not done-n.d.).…”