REFERENCES

Abstract:
RNA-protein interactions play important roles in almost every step of the lifetime of RNAs, such as RNA splicing, transporting, localization, translation and degradation. Post-translational modifications, such as O-GlcNAcylation and phosphorylation, and their "cross-talk" (OPCT) are essential to the activity and function regulation of RNA-binding proteins (RBPs). However, due to the extremely low abundance of O-GlcNAcylation and the lack of RBP-targeted enrichment strategies, large-scale simultaneous profiling of O-GlcNAcylation and phosphorylation on RBPs is still a challenging task. In the present study, we developed a tandem enrichment strategy combining metabolic labeling-based RNA tagging for selective purification of RBPs and HILIC-based enrichment for simultaneous O-GlcNAcylation and phosphorylation profiling. Benefiting from the sequence-independent RNA tagging by ethynyluridine (EU) labeling, 1115 RBPs binding to different types of RNAs were successfully enriched and identified by quantitative mass spectrometry (MS) analysis. Further HILIC enrichment on the tryptic-digested RBPs and MS analysis led to the first large-scale identification of O-GlcNAcylation and phosphorylation in the RNA-binding proteome, with 461 O-GlcNAc peptides corresponding to 300 RBPs and 671 phosphopeptides corresponding to 389 RBPs. Interestingly, ∼25% RBPs modified by two PTMs were found to be related to multiple metabolism pathways. This strategy has the advantage of high compatibility with MS and provides peptide-level evidence for the identification of O-GlcNAcylated RBPs. We expect it will support simultaneous mapping of O-GlcNAcylation and phosphorylation on RBPs and facilitate further elucidation of the crucial roles of OPCT in the function regulation of RBPs.

O-GlcNAc proteins:
NACAM, SAP18, PLOD2, NOP56, DDX3X, PLXB2, RRP8, SERA, PSMD3, MCA3, PRPF3, TPD54, TIM44, ACTN4, ACSL4, PLOD3, IF2P, ZC11A, SC22B, PR40A, MPPB, CSDE1, U520, NU155, EIF3G, SPF27, RL1D1, CLPX, RTN3, LC7L3, VAPB, SMC2, AP2A1, WIZ, BAG2, TOM40, ACL6A, EGFR, LMNA, TFR1, FRIH, RPN1, RPN2, ITB1, SYEP, HNRPC, SRPRA, VIME, GNAI3, ANXA5, LAMP1, ACADM, TOP1, TOP2A, PABP1, ADT3, TPR, EF2, PDIA4, FPPS, ENPL, ALDR, NDKA, RS2, UBF1, ARF4, NUCL, RAB6A, PSB1, FLNA, SDHB, UBA1, NDKB, ITA6, SFPQ, AT2B4, THIL, RS12, PSA4, SYVC, 1433T, MAP4, PSA5, PSB4, NDUS1, ECHM, KCY, AMRP, SDHA, METK2, CPSM, PUR9, HNRH1, 1433S, STIP1, P5CR1, MCM4, HSP74, CTNA1, MYH9, DEK, RL4, SPB5, NUP62, RBMX, TCPZ, ECE1, PRS6B, KI67, RAGP1, ATRX, SYQ, LMAN1, NASP, FAS, AL7A1, SYSC, MCM2, ACADV, NU153, RBP2, DNLI3, MRE11, CPT1A, F10A1, TCPD, RAB7A, IDH3G, HCFC1, DHB4, HDGF, ROA3, 6PGD, NUP98, ACLY, TCP4, SYYC, UBP14, SNAA, IF5, TERA, DSRAD, TPD52, EIF3B, NU107, EPIPL, SC61B, SRP54, B2MG, SMD2, RL23A, YBOX1, NOP14, IF4G2, GTF2I, NUCB2, RT22, HMGN5, RBM10, TFAM, CLH1, SPTB2, SET, CAP1, EXOSX, EWS, ODO1, RL18A, NUCB1, M2OM, LMNB2, SRS11, CALD1, RL18, C1QBP, CKAP4, KHDR1, DHX9, GOGA2, SSRP1, AHNK, AIMP1, ILF3, SRSF5, SRSF6, TIF1B, TCOF, PICAL, SNW1, TRI29, EIF3A, MLEC, CAPR1, SMC1A, RRP1B, GANAB, NUMA1, U5S1, RRS1, ACOX1, PLEC, RNPS1, PUM3, RB11B, SEPT7, DDB1, CDC37, SRSF7, PCKGM, HNRL2, INF2, PDS5A, PREP, RRP12, TOIP1, HP1B3, RBM26, BRE1A, CDKAL, PRP8, ZC3HE, QSOX2, IKIP, TM10C, EIF3M, PABP2, KTN1, CAND1, THOC6, P66A, MISP, CCAR1, PELP1, NDUF2, RM50, PAF1, TXND5, TOIP2, THOC2, TM263, NU133, PDC6I, SCFD1, LMO7, ELYS, RT27, HS105, NU205, RAD50, SMRC1, TNPO1, FUBP1, P5CR2, DNJA3, PTCD3, DDX27, EFGM, IWS1, NIBA2, YMEL1, PSMD1, EIF3C, ROAA, CMS1, MBB1A, GNL3, PDIP3, PININ, ACAD9, SFXN1, CYBP, RM47, RTN4, DDX21, AAAS, CARF, AATF, BCLF1, MYOF, SYLC, NXF1, SEC63, LIMA1, SEPT9, KAD3, RCOR1, ACINU, TMCO1, PPIE, PA2G4, RUVB2, TR150, RT23, CHTOP, TLN1, HYOU1, SAM50, SP16H, UTP18, SRPRB

Species: Homo sapiens

Abstract:
Glycosyltransferases carry out important cellular functions in species ranging from bacteria to humans. Despite their essential roles in biology, simple and robust activity assays that can be easily applied to high-throughput screening for inhibitors of these enzymes have been challenging to develop. Herein, we report a bead-based strategy to measure the group-transfer activity of glycosyltransferases sensitively using simple fluorescence measurements, without the need for coupled enzymes or secondary reactions. We validate the performance and accuracy of the assay using O-GlcNAc transferase (OGT) as a model system through detailed Michaelis-Menten kinetic analysis of various substrates and inhibitors. Optimization of this assay and application to high-throughput screening enabled screening for inhibitors of OGT, leading to a novel inhibitory scaffold. We believe this assay will prove valuable not only for the study of OGT, but also more widely as a general approach for the screening of glycosyltransferases and other group-transfer enzymes.

O-GlcNAc proteins:
HCFC1, CSK21, TAB1

Species: Homo sapiens

Abstract:
O-Linked β-N-acetylglucosamine (O-GlcNAc) is a monosaccharide that plays an essential role in cellular signaling throughout the nucleocytoplasmic proteome of eukaryotic cells. Strategies for selectively increasing O-GlcNAc levels on a target protein in cells would accelerate studies of this essential modification. Here, we report a generalizable strategy for introducing O-GlcNAc into selected target proteins in cells using a nanobody as a proximity-directing agent fused to O-GlcNAc transferase (OGT). Fusion of a nanobody that recognizes GFP (nGFP) or a nanobody that recognizes the four-amino acid sequence EPEA (nEPEA) to OGT yielded nanobody-OGT constructs that selectively delivered O-GlcNAc to a series of tagged target proteins (e.g., JunB, cJun, and Nup62). Truncation of the tetratricopeptide repeat domain as in OGT(4) increased selectivity for the target protein through the nanobody by reducing global elevation of O-GlcNAc levels in the cell. Quantitative chemical proteomics confirmed the increase in O-GlcNAc to the target protein by nanobody-OGT(4). Glycoproteomics revealed that nanobody-OGT(4) or full-length OGT produced a similar glycosite profile on the target protein JunB and Nup62. Finally, we demonstrate the ability to selectively target endogenous α-synuclein for O-GlcNAcylation in HEK293T cells. These first proximity-directed OGT constructs provide a flexible strategy for targeting additional proteins and a template for further engineering of OGT and the O-GlcNAc proteome in the future. The use of a nanobody to redirect OGT substrate selection for glycosylation of desired proteins in cells may further constitute a generalizable strategy for controlling a broader array of post-translational modifications in cells.

O-GlcNAc proteins:
SBNO1, CNOT1, P121C, DX39A, GTPB1, AP3B1, PGRC1, TAF4, EIF3F, IPO5, IF2B3, NOP56, DDX3X, ARI1A, IRS4, ANM5, TCRG1, PSA7, HGS, MYPT1, HNRDL, XPO1, SET1A, PUR4, NPC1, TIF1A, NKRF, OGT1, PPM1G, EIF3D, EIF3H, DHX15, SERA, HNRPR, IF4G3, E41L2, ZN207, BUB3, ACTN4, HTSF1, AP1G1, SYNC, AKAP8, CALU, SMCA5, JIP4, OGA, HNRPQ, DIAP1, TSN3, SNX2, DKC1, CLAP2, CPNE3, PHF2, ANR17, H2AY, FLNB, NCOR1, CISY, PR40A, SF3B1, CSDE1, U520, EIF3G, PRAF3, SRP72, MTA2, TOX4, SC24D, SC31A, SCAF4, ZRAB2, LC7L3, VAPB, IPO7, SC24B, ACSL3, AP2A1, AIFM1, LDHA, COX2, HPRT, AATM, PGK1, LMNA, TFR1, ALDOA, OAT, G3P, RPN1, RPN2, AT1A1, ADT2, PCCA, IF2A, RLA0, ITB1, ATPB, ENOA, PYGL, G6PI, NPM, LDHB, PDIA1, H10, TBB5, HEXB, PROF1, SYEP, HS90A, HNRPC, 4F2, HS90B, ASNS, ODPA, RU17, RSSA, SNRPA, GSTP1, HMGB1, DLDH, ROA1, PARP1, LKHA4, HS71B, H14, ODP2, THIO, CH60, BIP, HSP7C, EPB41, ODPB, LAMP1, ACADM, TOP1, TOP2A, PYC, C1TC, MPRI, PRPS2, PABP1, PCNA, HARS1, IMDH2, TPR, KCRB, XRCC6, XRCC5, EF2, PDIA4, PLST, GLU2B, KPYM, ENPL, PO2F1, HNRPL, SYDC, PLAK, ALDR, EZRI, GNS, RS2, CREB1, H12, AT2A2, JUNB, PYRG1, DDX5, PRS6A, TCPA, RL35A, RL7, VINC, SON, RCC1, NUCL, HXK1, E2AK2, SPEE, IF2B, ANXA7, LMNB1, FLNA, VDAC1, FBRL, PUR2, PUR6, UBA1, NDKB, ROA2, RFX1, TCEA1, SFPQ, PPIB, RS3, NFYA, SAHH, COF1, IF4B, EF1B, MCM3, BRD2, ATPA, PSA1, PSA3, PSA4, PAX6, U2AF2, RL13, PTBP1, SYTC, SYVC, EF1G, RFA1, APEX1, PYR1, CALR, MAP4, CALX, PSB5, TKT, PRDX6, PRDX5, PRDX3, RL12, PEBP1, PDIA3, 2AAA, CDC27, AMRP, SDHA, QCR1, PUR9, HNRH1, STIP1, PRDX2, RL9, CSTF2, MCM4, MCM5, MCM7, GLYM, HSP74, PHB, MYH9, COPB2, ADDA, BASI, FUS, NU214, DEK, MP2K2, ATPG, RL4, SRP14, NUP62, RBMX, GRP75, IF4A3, RS19, RL3, TXLNA, TCPZ, MDHC, MDHM, ECHA, IF2G, GARS, SYIC, LAP2A, LAP2B, MTREX, RS27, LPPRC, MATR3, RANG, VDAC2, UBP5, KI67, RAGP1, NOP2, CRKL, BAG6, RL27A, RL5, RL21, RL28, RS9, STT3A, COPD, PRC2A, TCPE, AL9A1, RL34, NASP, FAS, TCPG, EFTU, SYAC, SYSC, PSB3, MCM2, YLPM1, TMEDA, RBM25, NU153, RBP2, GSK3A, TAF6, GUAA, MRE11, GDIB, EMD, F10A1, LRBA, RL14, TCPQ, TCPD, ANX11, PAPOA, RAB7A, SMCA4, HCFC1, DHB4, ROA3, 6PGD, HNRPM, IMA1, AGFG1, HNRPF, MSH6, RBM5, NUP98, ACLY, COPB, COPA, MOT1, SC24C, SYRC, SYYC, AT1B3, RD23B, P5CS, IF5, XPO2, TERA, AFAD, DSRAD, PSA, SYMC, CTBP2, NU107, TPIS, ACTB, IF4A1, PSA6, ARF3, ABCE1, RAP1B, RS3A, RL26, RL15, S61A1, HNRPK, RS7, RS8, 1433E, RS14, RS23, RS11, SMD1, RL7A, RS4X, H4, RAN, RL23, GBB2, RL10A, RL11, RL8, PPIA, RL40, TRA2B, AP2B1, IF5A1, RACK1, YBOX1, EF1A1, TBB4B, CSK21, IF4G2, GTF2I, TCPB, PRKDC, RL24, RL19, SRSF3, FOXK1, RBM10, MPCP, CLH1, HNRPU, SPTB2, FOXK2, CAP1, LAT1, EXOSX, EWS, RL18A, FKBP4, RL6, TOP2B, KMT2A, LMNB2, TF65, IF4G1, TLE3, SRS11, PUR1, SUH, GABPA, PRDX1, RL18, C1QBP, KHDR1, SRSF1, DHX9, CD47, SSRP1, RBBP4, AHNK, AP1B1, NU160, BPTF, TP53B, AIMP1, ILF2, ILF3, LMAN2, TRAP1, PP1R8, ACACA, ROA0, PRDX4, CBX3, PSMD2, SRSF6, TIF1B, PTK7, PABP4, EIF3I, TCOF, SF3B2, TMED1, PICAL, RIPK1, HDAC1, CUL4B, CD166, IDI1, NFYC, CKAP5, HNRPD, SCRB2, DSG2, EIF3A, UBP2L, SCRIB, TTL12, DCTN1, DYHC1, SRC8, CAPR1, RBM39, MCM6, MDC1, EPN4, SMC1A, RRP1B, UBP10, GANAB, LBR, ZN638, IMB1, NUMA1, SEPT2, SART3, U5S1, SYK, BRD3, PDIA6, IPYR, TEBP, NONO, PWP2, RCN1, PCBP1, PCBP2, SF3B3, SAFB1, SF3A1, NCOA2, SF01, MARE1, NSDHL, TAB1, AAAT, VAS1, ZYX, CCDC6, PKN2, DDB1, CDC37, SRSF7, CPSF6, NRF1, H31T, QSER1, QRIC1, P3H1, TB10B, AMOT, DHB12, PRC2B, H2B2F, HP1B3, CE170, ZC3HD, RBM26, RIF1, RPRD2, ZN318, ECM29, ZMYM4, MAP1S, LIN54, EDC4, PRP8, SCYL2, NFRKB, ZC3HE, LARP1, FIP1, MCAF1, GGYF2, SPT6H, SND1, DHX30, KDM3B, ZCCHV, NUP54, POGZ, NUFP2, MAVS, I2BP2, RBBP6, HUWE1, YTHD3, CENPV, LYRIC, ZN598, GP180, CAND1, CARM1, DDX42, P66A, ARI3B, MGAP, PHF6, CHERP, ANKH1, SUGP1, CCAR1, SPB1, PHAR4, SPART, CCAR2, NUP93, S11IP, FNBP4, CPSF7, ARFG1, ENAH, AFG2H, TXND5, LS14A, Z280C, TNR6A, SMRC2, TBC15, PNPT1, HM13, PO210, GEMI5, ZN384, SMAP2, NU133, PDC6I, PCNP, CKAP2, ATX2L, P66B, ELYS, DDX1, GBF1, NICA, UBXN4, HS105, LAR4B, NU205, AKAP1, TFG, CBP, DDX17, CELF1, RENT1, SMRC1, FUBP2, TNPO1, UBP7, NCLN, FUBP1, FKB10, KBP, PDLI5, FUBP3, CHAP1, Z512B, ZFR, PRRC1, DOCK7, RBM14, VPS35, CIC, EFGM, SIN3A, MINT, CDC5L, PSMD1, EYA3, ATX2, HCD2, ACON, TS101, TCPH, ANM1, SH3G1, COR1B, DIDO1, HNRL1, DDX23, TMED9, NUP58, RBM4, NAA15, B2L13, YTHD1, UNK, ILKAP, SP130, BRD8, I2BPL, SLK, S6A15, PININ, NELFA, PTN23, WNK1, AMPB, GORS2, CYBP, TAF9B, GLOD4, CBX8, NCOA5, CHD8, APMAP, DCP1A, RTN4, ANLN, GEPH, PDLI7, DDX21, SYFB, SYIM, SMC4, RBM12, DDX18, CARF, UGGG1, CDK12, TECR, IF2B1, HPBP1, ITSN2, CNOT2, HACD3, RCC2, SYLC, SUCB1, UBQL2, PCYOX, S30BP, PUF60, NRBP, DACH1, BAZ2A, BAZ1B, CDC23, TASOR, ACINU, CDV3, MRTFB, YETS2, HECD1, PKCB1, DD19B, PRP19, MAGD2, FAF1, TRI33, SRRM2, PA2G4, RUVB2, RUVB1, VDAC3, E41L3, TR150, NOP58, SHLB1, LC7L2, TMED7, STRAP, RTCB, HBS1L, TLN1, HYOU1, PRC2C, SP16H, COPG1, DC1L1, S23IP