Ferritin is a translationally regulated heat shock protein of avian reticulocytes.
Heat-shock avian reticulocytes exhibit enhanced synthesis of a greater than 450-kDa protein. Biochemical, immunochemical, and visual criteria were used to identify this protein as the iron storage protein ferritin. The 21-kDa ferritin subunits synthesized during heat shock are similar in size and pI to the subunits that are constitutively synthesized. The 2-6-fold heat shock-induced increase in ferritin synthesis appears to be regulated at the translational level as it is insensitive to actinomycin D. Northern and dot-blot hybridization analyses of cytoplasmic RNAs with avian H-ferritin cDNA fragments support the contention that the heat shock stimulation of ferritin synthesis is translationally regulated. These latter studies demonstrate that the heat shock-induced synthesis of ferritin does not involve a change in the amount of total cytoplasmic ferritin mRNAs, but rather appears to entail a translocation of cytoplasmic H-ferritin mRNAs from a polyribosome-free, translationally repressed state to a polyribosome-associated, translationally active state. These results suggest that thermally stressed avian reticulocytes have a critical and functional need for the synthesis of additional ferritin and that its enhanced synthesis, unlike the new and/or enhanced synthesis of the well-established avian heat shock proteins, is regulated wholly at the translational level.
Atkinson
B G
BG
Department of Zoology, University of Western Ontario, London, Canada.
Blaker
T W
TW
Tomlinson
J
J
Dean
R L
RL
D000818:Animals; D003370:Coturnix; D004591:Electrophoresis, Polyacrylamide Gel; D005293:Ferritins / Q000096:biosynthesis / Q000097:blood* / Q000235:genetics; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000097:blood* / Q000235:genetics; D006358:Hot Temperature; D008970:Molecular Weight; D014176:Protein Biosynthesis; D012156:Reticulocytes / Q000378:metabolism*
D006360:Heat-Shock Proteins; D005293:Ferritins