Leucine methylation of protein phosphatase PP4C at C-terminal is critical for its cellular functions |
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Authors: | JungJin Lee Dong-Hyun Lee |
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Institution: | Department of Biological Sciences, College of Science, Chonnam National University, Gwangju 500-757, Republic of Korea |
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Abstract: | BackgroundProtein phosphatase 4 (PP4) has been known to have critical functions in DNA double strand break (DSB) repair and cell cycle by the regulation of phosphorylation of its target proteins, such as H2AX, RPA2, KAP-1, 53BP1. However, it is largely unknown how PP4 itself is regulated.MethodsWe examined the PP4C methylation on L307 at C-terminal by using methylated-leucine specific antibody. Then with PP4C L307A mutant, we explored that how nonmethylated form of PP4C affects its known cellular functions by immunoprecipitation, immunofluorescence, and DNA DSB repair assays.ResultsHere we show that PP4C is methylated on its C-terminal leucine residue in vivo and this methylation is important for cellular functions mediated by PP4. In the cells PP4C L307A mutant has significantly low activity of dephosphorylation against its known target proteins, and the loss of interaction between L307A PP4 mutant and regulatory subunits, R1, R2, or R3α/β causes the dissociation from its target proteins. Moreover, PP4C L307A mutant loses its role in both DSB repair pathways, HR (homologous recombination) and NHEJ (non-homologous end joining), which phenocopies PP4C depletion.ConclusionOur results demonstrate the key site of PP4C methylation and establish the physiological importance of this regulation. |
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Keywords: | DNA damage response Double-strand DNA breaks repair Protein phosphatase 4 Leucine methylation Homologous recombination Non-homologous end joining |
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