Dataset Information

Identification of SUMO-2/3-modified proteins associated with mitotic chromosomes

ABSTRACT: SUMO modification of proteins (sumoylation) is essential for mitotic progression from yeast to humans, but only a limited number of sumoylated proteins with functions in mitosis have been discovered. Vertebrates express three SUMO paralogs, SUMO-1, SUMO-2 and SUMO-3, but only SUMO-2 and -3 are chromosome-associated in mitosis. In this study, we used chromosome spreads to more precisely define the localization of endogenous SUMO-2 and -3 to the centromere as well as the chromosome protein scaffold. Furthermore, we developed methodologies for the immunopurification of endogenous SUMO-2 and -3 modified proteins from cell extracts. Using LC-MS/MS, we analyzed proteins immunopurified from mitotic chromosome fractions and G0 nuclear fractions. We identified 296 putative sumoylated proteins, with 138 being modified specifically in mitosis. We identified proteins known to localize to the centromere and kinetochore and the chromosome protein scaffold, consistent with SUMO-2/3 localization. Furthermore, we demonstrate that utilizing cell synchronization and fractionation allowed for the discovery of low abundance sumoylated proteins that are not detected in large asynchronous analyses. Our results provide a foundation for further characterization of the roles of sumoylation in regulating diverse aspects of chromosome segregation in mitosis. Thermo .raw files were uploaded to the ProHits (Liu et al, 2010) analytical suite and converted to .mzXML format using ReAdW software. Data were searched using X!Tandem (Craig & Beavis, 2004) against human ORFs (RefSeq v45). Search parameters specified a parent MS tolerance of +/- 15ppm, and an MS/MS tolerance of 0.4 Da, with up to two missed cleavages for trypsin. Oxidation of methionine and tryptophan, ubiquitylation of lysine, and alkylation of cysteine (by NEM) were allowed as variable modifications. Statistical validation of the results was performed using Peptide Prophet and Protein Prophet (Keller et al, 2002; Nesvizhskii et al, 2003) as part of the trans-proteomic pipeline. For each search, the Protein Prophet probability at a 1% false discovery rate was used as a cutoff value to generate SAINT-compatible input files. SAINT parameters were as follows: 5000 iterations, low mode Off (0), minFold 1 and normalization (1) (Choi et al, 2011). SAINT cutoff values of 0.75 were used to generate a high-confidence list of protein identifications.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Hela Cell

SUBMITTER: tharan srikumar

LAB HEAD: Michael J. Matunis

PROVIDER: PXD000381 | Pride | 2019-11-25

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	MM_8A2_SUMO23_G0_100_v1.mzXML	Mzxml
	MM_8A2_SUMO23_G0_100_v1.raw	Raw
	MM_8A2_SUMO23_G0_100_v1_gpm.pep.inter.prot.xml	Xml
	MM_8A2_SUMO23_G0_100_v1_gpm.pep.inter.xml	Xml
	MM_8A2_SUMO23_G0_100_v1_gpm.xml	Xml

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Identification of SUMO-2/3-modified proteins associated with mitotic chromosomes.

Cubeñas-Potts Caelin C Srikumar Tharan T Lee Christine C Osula Omoruyi O Subramonian Divya D Zhang Xiang-Dong XD Cotter Robert J RJ Raught Brian B Matunis Michael J MJ

Proteomics 20150107 4

Sumoylation is essential for progression through mitosis, but the specific protein targets and functions remain poorly understood. In this study, we used chromosome spreads to more precisely define the localization of SUMO-2/3 (small ubiquitin-related modifier) to the inner centromere and protein scaffold of mitotic chromosomes. We also developed methods to immunopurify proteins modified by endogenous, untagged SUMO-2/3 from mitotic chromosomes. Using these methods, we identified 149 chromosome- ...[more]

PMID: 25367092

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Project description:The essential process of dosage compensation equalizes X-chromosome gene expression between C. elegans XO males and XX hermaphrodites through a dosage compensation complex (DCC) that resembles condensin. The DCC binds to both X chromosomes of hermaphrodites to repress transcription by half. Here we show that post-translational modification by the SUMO conjugation pathway is essential for sex-specific assembly of the DCC onto X. Depletion of the SUMO peptide in vivo severely disrupts binding of particular DCC subunits and causes changes in X-linked gene expression similar to those caused by disrupting genes encoding DCC subunits. Three DCC subunits are themselves SUMOylated, and depletion of SUMO preferentially reduces their binding to X, suggesting that SUMOylation of DCC subunits is essential for robust association with X. DCC SUMOylation is triggered by the signal that initiates DCC assembly onto X. The initial step of assembly--binding of X-targeting factors to recruitment sites on X (rex sites)--is independent of SUMOylation, but robust binding of the complete complex requires SUMOylation. SUMOylated DCC subunits are enriched at rex sites, and SUMOylation enhances interactions between X-targeting factors and condensin subunits that facilitate DCC binding beyond the low level achieved without SUMOylation. DCC subunits also participate in condensin complexes essential for chromosome segregation, but their SUMOylation occurs only in the context of the DCC. Our results reinforce a newly emerging theme in which multiple proteins of a complex are SUMOylated in response to a specific stimulus, leading to accelerated complex formation and enhanced function. ChIP-chip experiments using antibodies against DPY-27, SDC-3, DPY-30, DPY-26, DPY-28 and FLAG-tagged SDC-2 in wild-type and smo-1 RNAi treated mixed embryos, with IGG controls. Also, sequential ChIP-chip experiments: (1) ChIP using FLAG antibodies to determine the genome-wide binding sites for SUMOylated proteins, (2) ChIP using FLAG antibodies followed by re-ChIP of eluted protein-chromatin complexes with DPY-27 antibodies to determine genome-wide binding sites for SUMOylated DPY-27 (referred to as DPY-27 re-ChIP experiments), (3) ChIP using FLAG antibodies followed by re-ChIP of eluted protein-chromatin with IGG antibodies to determine background binding (referred to as IGG re-ChIP experiments, and (4) ChIP using DPY-27 antibodies as a control to assess the efficiency of DPY-27 binding and detection in control vs. FLAG-tagged strains.