title: Phosphorylation of eIF2α on Threonine 169 is not required for Trypanosoma brucei cell cycle arrest during differentiation.
abstract: The trypanosome life cycle consists of a series of developmental forms each adapted to an environment in the relevant insect and/or mammalian host. The differentiation process from the mammalian bloodstream form to the insect-midgut procyclic form in Trypanosoma brucei occurs in two steps in vivo. First proliferating 'slender' bloodstream forms differentiate to non-dividing 'stumpy' forms arrested in G1. Second, in response to environmental cues, stumpy bloodstream forms re-enter the cell cycle and start to proliferate as procyclic forms after a lag during which both cell morphology and gene expression are modified. Nearly all arrested cells have lower rates of protein synthesis when compared to the proliferating equivalent. In eukaryotes, one mechanism used to regulate the overall rate of protein synthesis involves phosphorylation of the alpha subunit of initiation factor eIF2 (eIF2α). The effect of eIF2α phosphorylation is to prevent the action of eIF2B, the guanine nucleotide exchange factor that activates eIF2 for the next rounds of initiation. To investigate the role of the phosphorylation of eIF2α in the life cycle of T. brucei, a cell line was made with a single eIF2α gene that contained the phosphorylation site, threonine 169, mutated to alanine. These cells were capable of differentiating from proliferating bloodstream form cells into arrested stumpy forms in mice and into procyclic forms in vitro and in tsetse flies. These results indicate that translation attenuation mediated by the phosphorylation of eIF2α on threonine 169 is not necessary for the cell cycle arrest associated with these differentiation processes.
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Carla Cristi D C
authors.initials: CC
authors.lastname: Avila
authors.affiliation: Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU, UK; School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK.
authors.forename: Lori
authors.initials: L
authors.lastname: Peacock
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Fabricio Castro
authors.initials: FC
authors.lastname: Machado
authors.affiliation: School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK.
authors.forename: Wendy
authors.initials: W
authors.lastname: Gibson
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Sergio
authors.initials: S
authors.lastname: Schenkman
authors.affiliation: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK. Electronic address: mc115@cam.ac.uk.
authors.forename: Mark
authors.initials: M
authors.lastname: Carrington
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil. Electronic address: bacastilho@unifesp.br.
authors.forename: Beatriz A
authors.initials: BA
authors.lastname: Castilho
mesh_terms: D000818:Animals; D002460:Cell Line; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010442:Peptide Chain Initiation, Translational; D010766:Phosphorylation; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D014352:Trypanosomiasis / Q000469:parasitology*; D014370:Tsetse Flies / Q000469:parasitology
chemical_list: D015852:Eukaryotic Initiation Factor-2; D015800:Protozoan Proteins; D013912:Threonine
keywords: Cell cycle arrest; Differentiation; T. brucei; Translation initiation; eIF2