RESUMEN
CK2 is a ubiquitous but enigmatic kinase. The difficulty in assigning a role to CK2 centers on the fact that, to date, no biologically relevant modulator of its function has been identified. One common theme revolves around a constellation of known substrates involved in growth control, compatible with its concentration in the nucleus and nucleolus. We had previously described the identification of two catalytic subunits of CK2 in Trypanosoma brucei and characterized one of them. Here we report the characterization of the second catalytic subunit, CK2alpha', and the identification and characterization of the regulatory subunit CK2beta. All three subunits are primarily localized to the nucleolus in T. brucei. We also show that CK2beta interacts with the nucleolar protein NOG1, adding to the interaction map which previously linked CK2alpha to the nucleolar protein NOPP44/46, which in turn associates with the rRNA binding protein p37. CK2 activity has four distinctive features: near equal affinity for GTP and ATP, heparin sensitivity, and stimulation by polyamines and polybasic peptides. Sequence comparison shows that the parasite orthologues have mutations in residues previously mapped as important in specifying affinity for GTP and stimulation by both polyamines and polybasic peptides. Studies of the enzymatic activity of the T. brucei CK2s show that both the affinity for GTP and stimulation by polyamines have been lost and only the features of heparin inhibition and stimulation by polybasic peptides are conserved.
Asunto(s)
Quinasa de la Caseína II/metabolismo , Trypanosoma brucei brucei/enzimología , Secuencia de Aminoácidos , Animales , Quinasa de la Caseína II/química , Quinasa de la Caseína II/genética , Quinasa de la Caseína II/aislamiento & purificación , Núcleo Celular/metabolismo , Secuencia Conservada , Regulación del Desarrollo de la Expresión Génica , Humanos , Isoenzimas/genética , Isoenzimas/aislamiento & purificación , Isoenzimas/metabolismo , Datos de Secuencia Molecular , Unión Proteica , Interferencia de ARN , Alineación de Secuencia , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/crecimiento & desarrolloRESUMEN
We have generalized the derivation of genetic-interaction networks from quantitative phenotype data. Familiar and unfamiliar modes of genetic interaction were identified and defined. A network was derived from agar-invasion phenotypes of mutant yeast. Mutations showed specific modes of genetic interaction with specific biological processes. Mutations formed cliques of significant mutual information in their large-scale patterns of genetic interaction. These local and global interaction patterns reflect the effects of gene perturbations on biological processes and pathways.