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J Biol Chem. 2015 May 8;290(19):12040-7. doi: 10.1074/jbc.M115.641530. Epub 2015 Mar 20.

A Proteomic Strategy Identifies Lysine Methylation of Splicing Factor snRNP70 by the SETMAR Enzyme.

Author information

1
From the Department of Biology and scottmc@stanford.edu.
2
From the Department of Biology and Department of Chemical and Systems Biology, School of Medicine, Stanford University, Stanford, California 94305.
3
From the Department of Biology and.
4
Department of Chemical and Systems Biology, School of Medicine, Stanford University, Stanford, California 94305.
5
From the Department of Biology and ogozani@stanfordedu.

Abstract

The lysine methyltransferase (KMT) SETMAR is implicated in the response to and repair of DNA damage, but its molecular function is not clear. SETMAR has been associated with dimethylation of histone H3 lysine 36 (H3K36) at sites of DNA damage. However, SETMAR does not methylate H3K36 in vitro. This and the observation that SETMAR is not active on nucleosomes suggest that H3K36 methylation is not a physiologically relevant activity. To identify potential non-histone substrates, we utilized a strategy on the basis of quantitative proteomic analysis of methylated lysine. Our approach identified lysine 130 of the mRNA splicing factor snRNP70 as a SETMAR substrate in vitro, and we show that the enzyme primarily generates monomethylation at this position. Furthermore, we show that SETMAR methylates snRNP70 Lys-130 in cells. Because snRNP70 is a key early regulator of 5' splice site selection, our results suggest a model in which methylation of snRNP70 by SETMAR regulates constitutive and/or alternative splicing. In addition, the proteomic strategy described here is broadly applicable and is a promising route for large-scale mapping of KMT substrates.

KEYWORDS:

Histone Methylation; Mass Spectrometry (MS); Protein Methylation; Proteomics; Substrate Specificity

PMID:
25795785
PMCID:
PMC4424340
DOI:
10.1074/jbc.M115.641530
[Indexed for MEDLINE]
Free PMC Article

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