Arginine methylation next to the PY-NLS modulates Transportin binding and nuclear import of FUS

Abstract

Fused in sarcoma (FUS) is a nuclear protein that carries a proline-tyrosine nuclear localization signal (PY-NLS) and is imported into the nucleus via Transportin (TRN). Defects in nuclear import of FUS have been implicated in neurodegeneration, since mutations in the PY-NLS of FUS cause amyotrophic lateral sclerosis (ALS). Moreover, FUS is deposited in the cytosol in a subset of frontotemporal lobar degeneration (FTLD) patients. Here, we show that arginine methylation modulates nuclear import of FUS via a novel TRN-binding epitope. Chemical or genetic inhibition of arginine methylation restores TRN-mediated nuclear import of ALS-associated FUS mutants. The unmethylated arginine-glycine-glycine domain preceding the PY-NLS interacts with TRN and arginine methylation in this domain reduces TRN binding. Inclusions in ALS-FUS patients contain methylated FUS, while inclusions in FTLD-FUS patients are not methylated. Together with recent findings that FUS co-aggregates with two related proteins of the FET family and TRN in FTLD-FUS but not in ALS-FUS, our study provides evidence that these two diseases may be initiated by distinct pathomechanisms and implicates alterations in arginine methylation in pathogenesis.

The FUS about arginine methylation in ALS and FTLD

“…Methylation of the RGG3 peptide completely prevented this binding. Through these experiments Dormann et al (2012) were able to show for the first time that residues outside of the PY-NLS can be involved in FUS nuclear import. Furthermore, they were able to establish a working model by which this occurs: they propose that in normal situations, the PY-NLS anchors the FUS C-terminus to TRN and the adjacent RGG repeats stabilize the interaction.…”

“…In recent times, it has been established that this arginine methylation can affect their nuclear localization (Araya et al, 2005;Jobert et al, 2009;Tradewell et al, 2012). In this issue, Dormann et al (2012) sought to delve further into the mechanism by which this occurs. They began their studies in a similar fashion to Tradewell and colleagues, by confirming that inhibiting global arginine methylation using the general methylation inhibitor, adenosine-2,3-dialdehyde (AdOx) could restore the lost nuclear localization of both HA-tagged cytoplasmic ALS-causing mutants and cytoplasmic EWS and TAF15 point mutants in HeLa cells.…”

“…Accordingly, Dormann et al (2012) have identified that methylation of the Fused in sarcoma (FUS) RGG3 domain is involved in the cytoplasmic mislocalisation of ALS-FUS mutants, through a transportin-dependent mechanism. By contrast, hypomethylation in this domain may play a role in the aberrant accumulation of FUS in FTLD-FUS.…”

Activity-dependent FUS dysregulation disrupts synaptic homeostasis

“…Nucleocytoplasmic shuttling of FUS occurs by a nonclassical proline-tyrosine nuclear localization signal (PY-NLS) and a nuclear export signal (NES) (10). Methylation of the C-terminal RGG3 domain of FUS is necessary for transportin 1 interaction and nuclear localization (11).…”

Methylation of the nuclear poly(A)-binding protein by type I protein arginine methyltransferases – how and why

“…FUS is known to carry asymmetrically dimethylated arginine residues; in contrast to PABPN1, these are not in the canonical motifs of the transportin-binding site but in an adjacent RGG domain (Rappsilber et al , 2003 ). The inhibition of arginine methylation by the use of the general inhibitor adenosine dialdehyde, knockdown of PRMT1, or deletion of the PRMT1 gene rescued the nuclear import of FUS when it was compromised by mutations in its PY-NLS (Dormann et al , 2012 ;Tradewell et al , 2012 ). As in the case of PABPN1, the binding of FUS to transportin was reduced by arginine methylation (Fronz et al , 2011 ;Dormann et al , 2012 ).…”