PRMT1-mediated arginine methylation of PIAS1 regulates STAT1 signaling

Abstract

To elucidate the function of the transcriptional coregulator PRMT1 (protein arginine methyltranferase 1) in interferon (IFN) signaling, we investigated the expression of STAT1 (signal transducer and activator of transcription) target genes in PRMT1-depleted cells. We show here that PRMT1 represses a subset of IFNginducible STAT1 target genes in a methyltransferase-dependent manner. These genes are also regulated by the STAT1 inhibitor PIAS1 (protein inhibitor of activated STAT1). PIAS1 is arginine methylated by PRMT1 in vitro as well as in vivo upon IFN treatment. Mutational and mass spectrometric analysis of PIAS1 identifies Arg 303 as the single methylation site. Using both methylation-deficient and methylation-mimicking mutants, we find that arginine methylation of PIAS1 is essential for the repressive function of PRMT1 in IFN-dependent transcription and for the recruitment of PIAS1 to STAT1 target gene promoters in the late phase of the IFN response. Methylation-dependent promoter recruitment of PIAS1 results in the release of STAT1 and coincides with the decline of STAT1-activated transcription. Accordingly, knockdown of PRMT1 or PIAS1 enhances the antiproliferative effect of IFNg. Our findings identify PRMT1 as a novel and crucial negative regulator of STAT1 activation that controls PIAS1-mediated repression by arginine methylation.[Keywords: Transcriptional repression; interferon signaling; STAT1; PIAS1; PRMT1; arginine methylation] Supplemental material is available at http://www.genesdev.org.

Mechanism of inhibiting type I interferon induction by hepatitis B virus X protein

“…For example, HBx enhances HBV replication and secretion of surface and precore protein in HepG2 cells but not in Huh7 cells (Melegari et al, 1998). On the other hand, the decreased function of transcriptional coregulator PRMT1 on STAT1 methylation, which was reported to account for the reduction of transcriptional activity of STAT1 (Christen et al, 2007), is challenged by the finding that PRMT1 mediates arginine methylation of protein inhibitor of activated STAT1 (PIAS1) instead, leading to repression of IFN-inducible transcription via promoting the release of STAT1 from target gene promoter (Weber et al, 2009). …”

PIAS proteins: pleiotropic interactors associated with SUMO

“…Interestingly, the serine residue is conserved in PIAS2 and PIAS3, but it is currently not known if they are also targeted by IKKa. PIAS1 was recently also found to be dimethylated on R303, located between the PINIT motif and SP-RING domain, by protein arginine methyltransferase 1 (PRMT1) in response to interferon [108], which resulted in repression of STAT1 signaling. It is possible that also PIAS2 and PIAS3 are targeted by PRMT1, since the region encompassing the R residue is fully conserved in them.…”

Establishment of an ectopically expressed and functional PRMT1 for proteomic analysis of arginine‐methylated proteins

“…Accordingly, ectopic expression of PRMT1 enhanced the methylation levels of cellular proteins when detected by fluorography using Chao-Hsiung Lin 5,6 Wey-Jinq Lin tritium-labeled SAM as a methyl donor. Proteins with upregulated methylation were resolved by 2-DE and identified using MS/MS.…”

“…However, the regulatory detail of PRMT1 in terms of substrate selection and catalytic activity is not fully understood. While methylated arginine residues are frequently found in the glycine-and argininerich (GAR) motifs or RXR sequences of PRMT1 substrates[2], arginine methylation of some other substrates does not occur in either of these contexts [5,6]. Identification and analysis of more methyl acceptors will further elucidate essential elements of substrate recognition.…”