1.Mitotic phosphorylation of eukaryotic initiation factor 4G1 (eIF4G1) at Ser1232 by Cdk1:cyclin B inhibits eIF4A helicase complex binding with RNA.
Dobrikov MI1, Shveygert M, Brown MC, Gromeier M. Mol Cell Biol. 2014 Feb;34(3):439-51. doi: 10.1128/MCB.01046-13. Epub 2013 Nov 18.
During mitosis, global translation is suppressed, while synthesis of proteins with vital mitotic roles must go on. Prior evidence suggests that the mitotic translation shift involves control of initiation. Yet, no signals specifically targeting translation initiation factors during mitosis have been identified. We used phosphoproteomics to investigate the central translation initiation scaffold and "ribosome adaptor," eukaryotic initiation factor 4G1 (eIF4G1) in interphase or nocodazole-arrested mitotic cells. This approach and kinase inhibition assays, in vitro phosphorylation with recombinant kinase, and kinase depletion-reconstitution experiments revealed that Ser1232 in eIF4G1 is phosphorylated by cyclin-dependent kinase 1 (Cdk1):cyclin B during mitosis. Ser1232 is located in an unstructured region of the C-terminal portion of eIF4G1 that coordinates assembly of the eIF4G/-4A/-4B helicase complex and binding of the mitogen-activated protein kinase (MAPK) signal-integrating kinase, Mnk.
2.Characterization of two T. gondii CK1 isoforms.
Donald RG1, Zhong T, Meijer L, Liberator PA. Mol Biochem Parasitol. 2005 May;141(1):15-27.
Previous affinity chromatography experiments have described the unexpected binding of an isoform of casein kinase I (CK1) from Leishmania mexicana, Trypanosoma cruzi, Plasmodium falciparum and Toxoplasma gondii to an immobilized cyclin-dependent kinase (CDK) inhibitor (purvalanol B). In order to further evaluate CK1 as a potential anti-parasitic target, two T. gondii CK1 genes were cloned by PCR using primers derived from a putative CK1 gene fragment identified from a T. gondii EST database. The genes are predicted to encode a smaller polypeptide of 38 kDa (TgCK1alpha) and larger 49 kDa isoform bearing a C-terminal extension (TgCK1beta). Enzymatically active recombinant FLAG-epitope tagged TgCK1alpha and TgCK1beta enzymes were immuno-precipitated from transiently transfected T. gondii parasites. While TgCK1alpha expression was found to be cytosolic, TgCK1beta was expressed predominantly at the plasma membrane. Deletion mapping showed that the C-terminal domain of TgCK1beta confers this membrane-association.
3.An evolutionary conserved role of Wnt signaling in stem cell fate decision.
Teo R1, Möhrlen F, Plickert G, Müller WA, Frank U. Dev Biol. 2006 Jan 1;289(1):91-9. Epub 2005 Nov 23.
Wnt/Frizzled/ss-catenin-based signaling systems play diverse roles in metazoan development, being involved not only in the establishment of body axes in embryogenesis but also in regulating stem cell fate in mammalian post-embryonic development. We have studied the role the canonical Wnt cascade plays in stem cell fate determination in Hydractinia, a member of the ancient metazoan phylum Cnidaria, by analyzing two key molecules in this pathway, frizzled and ss-catenin, and blocking GSK-3. Generally, frizzled was expressed in cells able to divide but absent in post-mitotic, terminally differentiated cells such as nerve cells and nematocytes. Transcripts of frizzled were identified in all embryonic stages beginning with maternal transcripts in the oocyte. Following gastrulation and in the planula larva, frizzled expression concentrated in the central endodermal mass from which the first interstitial stem cells and their derivatives arise. In post-metamorphic development, high levels of frizzled transcripts were detected in interstitial stem cells.