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The multifunctional poly(A)-binding protein (PABP) 1 is subject to extensive dynamic post-translational modification, which molecular modelling suggests plays an important role in co-ordinating its activities.

Brook M, McCracken L, Reddington JP, Lu ZL, Morrice NA, Gray NK - Biochem. J. (2012)

Bottom Line: Intriguingly, PABP1 contains glutamate and aspartate methylations, modifications of unknown function in eukaryotes, as well as lysine and arginine methylations, and lysine acetylations.The latter dramatically alter the pI of PABP1, an effect also observed during the cell cycle, suggesting that different biological processes/stimuli can regulate its modification status, although PABP1 also probably exists in differentially modified subpopulations within cells.Modelling using available structures implicates these modifications in regulating interactions with individual PAM2 (PABP-interacting motif 2)-containing proteins, suggesting a direct link between PABP1 modification status and the formation of distinct mRNP (messenger ribonucleoprotein) complexes that regulate mRNA fate in the cytoplasm.

View Article: PubMed Central - PubMed

Affiliation: MRC Centre for Reproductive Health/MRC Human Reproductive Sciences Unit, Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, Scotland, UK. matt.brook@ed.ac.uk

ABSTRACT
PABP1 [poly(A)-binding protein 1] is a central regulator of mRNA translation and stability and is required for miRNA (microRNA)-mediated regulation and nonsense-mediated decay. Numerous protein, as well as RNA, interactions underlie its multi-functional nature; however, it is unclear how its different activities are co-ordinated, since many partners interact via overlapping binding sites. In the present study, we show that human PABP1 is subject to elaborate post-translational modification, identifying 14 modifications located throughout the functional domains, all but one of which are conserved in mouse. Intriguingly, PABP1 contains glutamate and aspartate methylations, modifications of unknown function in eukaryotes, as well as lysine and arginine methylations, and lysine acetylations. The latter dramatically alter the pI of PABP1, an effect also observed during the cell cycle, suggesting that different biological processes/stimuli can regulate its modification status, although PABP1 also probably exists in differentially modified subpopulations within cells. Two lysine residues were differentially acetylated or methylated, revealing that PABP1 may be the first example of a cytoplasmic protein utilizing a 'methylation/acetylation switch'. Modelling using available structures implicates these modifications in regulating interactions with individual PAM2 (PABP-interacting motif 2)-containing proteins, suggesting a direct link between PABP1 modification status and the formation of distinct mRNP (messenger ribonucleoprotein) complexes that regulate mRNA fate in the cytoplasm.

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PABP1 is arginine dimethylated independently of PRMT4PABP1 was immunoprecipitated from Prmt4+/+ and Prmt4−/− MEFs (A) or HeLa cells (B) and Western blotted using anti-(dimethyl-Arg455/Arg460-PABP1), anti-(symmetrically dimethylated arginine) (SYM10), anti-(asymmetrically dimethylated arginine) (ASYM24) or anti-PABP1 antibodies (A, right-hand panel; B, bottom panel). The anti-(methyl-arginine) antibodies also detected additional methylated antigens (marked with *) in PABP1 immunoprecipitates. Molecular mass in kDa is indicated.
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Figure 2: PABP1 is arginine dimethylated independently of PRMT4PABP1 was immunoprecipitated from Prmt4+/+ and Prmt4−/− MEFs (A) or HeLa cells (B) and Western blotted using anti-(dimethyl-Arg455/Arg460-PABP1), anti-(symmetrically dimethylated arginine) (SYM10), anti-(asymmetrically dimethylated arginine) (ASYM24) or anti-PABP1 antibodies (A, right-hand panel; B, bottom panel). The anti-(methyl-arginine) antibodies also detected additional methylated antigens (marked with *) in PABP1 immunoprecipitates. Molecular mass in kDa is indicated.

Mentions: PRMT4, and other type 1 PRMTs (PRMT1, 3, 6 and 8), asymmetrically dimethylate arginine. In Prmt4−/− MEFs, the amount of asymmetrically dimethylated arginine in PABP1 is dramatically decreased, but not abrogated (Figure 2A; ASYM24, [14]), consistent with a role for other type 1 PRMTs. Since the anti-(methyl-Arg455/Arg460 PABP1) antibody (Figure 2A) detects reduced but persistent dimethylation in Prmt4−/− MEFs, the sites for these other type 1 PRMTs must include one or both of these residues. In contrast, type 2 PRMTs (PRMT5, 7 and 9) catalyse symmetrical arginine dimethylation which was not detected in PABP1 (Figure 2A; SYM10), although readily detected in other proteins present within input lysates (Supplementary Figure S3 at http://www.BiochemJ.org/bj/441/bj4410803add.htm). This suggests that PABP1 is not a Type 2 PRMT substrate in MEFs.


The multifunctional poly(A)-binding protein (PABP) 1 is subject to extensive dynamic post-translational modification, which molecular modelling suggests plays an important role in co-ordinating its activities.

Brook M, McCracken L, Reddington JP, Lu ZL, Morrice NA, Gray NK - Biochem. J. (2012)

PABP1 is arginine dimethylated independently of PRMT4PABP1 was immunoprecipitated from Prmt4+/+ and Prmt4−/− MEFs (A) or HeLa cells (B) and Western blotted using anti-(dimethyl-Arg455/Arg460-PABP1), anti-(symmetrically dimethylated arginine) (SYM10), anti-(asymmetrically dimethylated arginine) (ASYM24) or anti-PABP1 antibodies (A, right-hand panel; B, bottom panel). The anti-(methyl-arginine) antibodies also detected additional methylated antigens (marked with *) in PABP1 immunoprecipitates. Molecular mass in kDa is indicated.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3298439&req=5

Figure 2: PABP1 is arginine dimethylated independently of PRMT4PABP1 was immunoprecipitated from Prmt4+/+ and Prmt4−/− MEFs (A) or HeLa cells (B) and Western blotted using anti-(dimethyl-Arg455/Arg460-PABP1), anti-(symmetrically dimethylated arginine) (SYM10), anti-(asymmetrically dimethylated arginine) (ASYM24) or anti-PABP1 antibodies (A, right-hand panel; B, bottom panel). The anti-(methyl-arginine) antibodies also detected additional methylated antigens (marked with *) in PABP1 immunoprecipitates. Molecular mass in kDa is indicated.
Mentions: PRMT4, and other type 1 PRMTs (PRMT1, 3, 6 and 8), asymmetrically dimethylate arginine. In Prmt4−/− MEFs, the amount of asymmetrically dimethylated arginine in PABP1 is dramatically decreased, but not abrogated (Figure 2A; ASYM24, [14]), consistent with a role for other type 1 PRMTs. Since the anti-(methyl-Arg455/Arg460 PABP1) antibody (Figure 2A) detects reduced but persistent dimethylation in Prmt4−/− MEFs, the sites for these other type 1 PRMTs must include one or both of these residues. In contrast, type 2 PRMTs (PRMT5, 7 and 9) catalyse symmetrical arginine dimethylation which was not detected in PABP1 (Figure 2A; SYM10), although readily detected in other proteins present within input lysates (Supplementary Figure S3 at http://www.BiochemJ.org/bj/441/bj4410803add.htm). This suggests that PABP1 is not a Type 2 PRMT substrate in MEFs.

Bottom Line: Intriguingly, PABP1 contains glutamate and aspartate methylations, modifications of unknown function in eukaryotes, as well as lysine and arginine methylations, and lysine acetylations.The latter dramatically alter the pI of PABP1, an effect also observed during the cell cycle, suggesting that different biological processes/stimuli can regulate its modification status, although PABP1 also probably exists in differentially modified subpopulations within cells.Modelling using available structures implicates these modifications in regulating interactions with individual PAM2 (PABP-interacting motif 2)-containing proteins, suggesting a direct link between PABP1 modification status and the formation of distinct mRNP (messenger ribonucleoprotein) complexes that regulate mRNA fate in the cytoplasm.

View Article: PubMed Central - PubMed

Affiliation: MRC Centre for Reproductive Health/MRC Human Reproductive Sciences Unit, Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, Scotland, UK. matt.brook@ed.ac.uk

ABSTRACT
PABP1 [poly(A)-binding protein 1] is a central regulator of mRNA translation and stability and is required for miRNA (microRNA)-mediated regulation and nonsense-mediated decay. Numerous protein, as well as RNA, interactions underlie its multi-functional nature; however, it is unclear how its different activities are co-ordinated, since many partners interact via overlapping binding sites. In the present study, we show that human PABP1 is subject to elaborate post-translational modification, identifying 14 modifications located throughout the functional domains, all but one of which are conserved in mouse. Intriguingly, PABP1 contains glutamate and aspartate methylations, modifications of unknown function in eukaryotes, as well as lysine and arginine methylations, and lysine acetylations. The latter dramatically alter the pI of PABP1, an effect also observed during the cell cycle, suggesting that different biological processes/stimuli can regulate its modification status, although PABP1 also probably exists in differentially modified subpopulations within cells. Two lysine residues were differentially acetylated or methylated, revealing that PABP1 may be the first example of a cytoplasmic protein utilizing a 'methylation/acetylation switch'. Modelling using available structures implicates these modifications in regulating interactions with individual PAM2 (PABP-interacting motif 2)-containing proteins, suggesting a direct link between PABP1 modification status and the formation of distinct mRNP (messenger ribonucleoprotein) complexes that regulate mRNA fate in the cytoplasm.

Show MeSH
Related in: MedlinePlus