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Molecular and Cellular Biology, March 2006, p. 1644-1653, Vol. 26, No. 5
0270-7306/06/$08.00+0 doi:10.1128/MCB.26.5.1644-1653.2006
M. Christine Hollander,2,
Georgina F. Miller,3 and
Albert J. Fornace Jr.2*
NIH-GWU Graduate Partnerships Program in Genetics,1 Gene Response Section, Center for Cancer Research, NCI,2 Division of Veterinary Resources, NIH, Bethesda, Maryland3
Received 15 December 2004/ Returned for modification 21 January 2005/ Accepted 8 December 2005
The protein encoded by growth arrest and DNA damage-inducible transcript 34 (Gadd34) is associated with translation initiation regulation following certain stress responses. Through interaction with the protein phosphatase 1 catalytic subunit (PP1c), Gadd34 recruits PP1c for the removal of an inhibitory phosphate group on the
subunit of elongation initiation factor 2, thereby reversing the shutoff of protein synthesis initiated by stress-inducible kinases. In the absence of stress, the physiologic consequences of Gadd34 function are not known. Initial analysis of Gadd34-null mice revealed several significant findings, including hypersplenism, decreased erythrocyte volume, increased numbers of circulating erythrocytes, and decreased hemoglobin content, resembling some thalassemia syndromes. Biochemical analysis of the hemoglobin-producing reticulocyte (an erythrocyte precursor) revealed that the decreased hemoglobin content in the Gadd34-null erythrocyte is due to the reduced initiation of the globin translation machinery. We propose that an equilibrium state exists between Gadd34/PP1c and the opposing heme-regulated inhibitor kinase during hemoglobin synthesis in the reticulocyte.
Present address: Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Present address: Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20889.
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