Article

The tRNA methylase METTL1 is phosphorylated and inactivated by PKB and RSK in vitro and in cells.

MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK.
The EMBO Journal (Impact Factor: 10.75). 06/2005; 24(9):1696-705. DOI: 10.1038/sj.emboj.7600648
Source: PubMed

ABSTRACT A substrate for protein kinase B (PKB)alpha in HeLa cell extracts was identified as methyltransferase-like protein-1 (METTL1), the orthologue of trm8, which catalyses the 7-methylguanosine modification of tRNA in Saccharomyces cerevisiae. PKB and ribosomal S6 kinase (RSK) both phosphorylated METTL1 at Ser27 in vitro. Ser27 became phosphorylated when HEK293 cells were stimulated with insulin-like growth factor-1 (IGF-1) and this was prevented by inhibition of phosphatidyinositol 3-kinase. The IGF-1-induced Ser27 phosphorylation did not occur in 3-phosphoinositide-dependent protein kinase-1 (PDK1)-deficient embryonic stem cells, but occurred normally in PDK1[L155E] cells, indicating that the effect of IGF-1 is mediated by PKB. METTL1 also became phosphorylated at Ser27 in response to phorbol-12-myristate 13-acetate and this was prevented by PD 184352 or pharmacological inhibition of RSK. Phosphorylation of METTL1 by PKB or RSK inactivated METTL1 in vitro, as did mutation of Ser27 to Asp or Glu. Expression of METTL1[S27D] or METTL1[S27E] did not rescue the growth phenotype of yeast lacking trm8. In contrast, expression of METTL1 or METTL1[S27A] partially rescued growth. These results demonstrate that METTL1 is inactivated by PKB and RSK in cells, and the potential implications of this finding are discussed.

Download full-text

Full-text

Available from: Axel Knebel, Jul 02, 2015
0 Followers
 · 
92 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Loss of N7-methylguanosine (m7G) modification is involved in the recently discovered rapid tRNA degradation pathway. In yeast, this modification is catalyzed by the heterodimeric complex composed of a catalytic subunit Trm8 and a noncatalytic subunit Trm82. We have solved the crystal structure of Trm8 alone and in complex with Trm82. Trm8 undergoes subtle conformational changes upon Trm82 binding which explains the requirement of Trm82 for activity. Cocrystallization with the S-adenosyl-methionine methyl donor defines the putative catalytic site and a guanine binding pocket. Small-angle X-ray scattering in solution of the Trm8-Trm82 heterodimer in complex with tRNA(Phe) has enabled us to propose a low-resolution structure of the ternary complex which defines the tRNA binding mode of Trm8-Trm82 and the structural elements contributing to specificity.
    Structure 02/2008; 16(1):52-61. DOI:10.1016/j.str.2007.10.025 · 6.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Yeast tRNA (m(7)G46) methyltransferase contains two protein subunits (Trm8 and Trm82). To address the RNA recognition mechanism of the Trm8-Trm82 complex, we investigated methyl acceptance activities of eight truncated yeast tRNA(Phe) transcripts. Both the D-stem and T-stem structures were required for efficient methyl-transfer. To clarify the role of the D-stem structure, we tested four mutant transcripts, in which tertiary base pairs were disrupted. The tertiary base pairs were important but not essential for the methyl-transfer to yeast tRNA(Phe) transcript, suggesting that these base pairs support the induced fit of the G46 base into the catalytic pocket.
    FEBS Letters 05/2007; 581(8):1599-604. DOI:10.1016/j.febslet.2007.03.023 · 3.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A protein expressed in immune cells and muscle was detected in muscle extracts as a substrate for several SAPKs (stress-activated protein kinases). It interacted specifically with the F-actin capping protein CapZ in splenocytes, and was therefore termed 'CapZIP' (CapZ-interacting protein). Human CapZIP was phosphorylated at Ser-179 and Ser-244 by MAPKAP-K2 (mitogen-activated protein kinase-activated protein kinase 2) or MAPKAP-K3 in vitro. Anisomycin induced the phosphorylation of CapZIP at Ser-179 in Jurkat cells, which was prevented by SB 203580, consistent with phosphorylation by MAPKAP-K2 and/or MAPKAP-K3. However, osmotic shock-induced phosphorylation of Ser-179 was unaffected by SB 203580. These and other results suggest that CapZIP is phosphorylated at Ser-179 in cells by MAPKAP-K2/MAPKAP-K3, and at least one other protein kinase. Stress-activated MAP kinase family members phosphorylated human CapZIP at many sites, including Ser-68, Ser-83, Ser-108 and Ser-216. Ser-108 became phosphorylated when Jurkat cells were exposed to osmotic shock, which was unaffected by SB 203580 and/or PD 184352, or in splenocytes from mice that do not express either SAPK3/p38gamma or SAPK4/p38delta. Our results suggest that CapZIP may be phosphorylated by JNK (c-Jun N-terminal kinase), which phosphorylates CapZIP to >5 mol/mol within minutes in vitro. Osmotic shock or anisomycin triggered the dissociation of CapZIP from CapZ in Jurkat cells, suggesting that phosphorylation of CapZIP may regulate the ability of CapZ to remodel actin filament assembly in vivo.
    Biochemical Journal 07/2005; 389(Pt 1):127-35. DOI:10.1042/BJ20050387 · 4.78 Impact Factor