A fission yeast general translation factor reveals links between protein synthesis and cell cycle controls.
In two independent screens we isolated fission yeast mutations with phenotypes suggesting defects in B-cyclin function or expression. These mutations define a single gene which we call ded1. We show that ded1 encodes a general translation factor that is related in sequence and function to RNA helicases required for translation in other species. Levels of the B-cyclins Cig2 and Cdc13 are dramatically reduced upon inactivation of Ded1, and this reduction is independent of degradation by the anaphase promoting complex. When a ded1 mutant is grown under semi-restrictive conditions, the translation of Cig2 (and to a lesser extent Cdc13), is impaired relative to other proteins. We show that B-cyclin translation is specifically inhibited upon nitrogen starvation of wild-type cells, when B-cyclin/Cdc2 inactivation is a prerequisite for G(1) arrest and subsequent mating. Our data suggest that translational inhibition of B-cyclin expression represents a third mechanism, in addition to cyclin degradation and Rum1 inhibition, that contributes to Cdc2 inactivation as cells exit from the mitotic cell cycle and prepare for meiosis.
Grallert
B
B
Imperial Cancer Research Fund, Lincoln's Inn Fields, London, WC2A 3PX, UK.
Kearsey
S E
SE
Lenhard
M
M
Carlson
C R
CR
Nurse
P
P
Boye
E
E
Labib
K
K
D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D053487:DEAD-box RNA Helicases; D005656:Fungal Proteins / Q000502:physiology*; D005800:Genes, Fungal; D014176:Protein Biosynthesis; D020365:RNA Helicases / Q000502:physiology; D012568:Schizosaccharomyces / Q000166:cytology* / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D029702:Schizosaccharomyces pombe Proteins; C492151:sum3 protein, S pombe; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases