Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Regulation of an eukaryotic initiation factor-2 (eIF-2) associated 67 kDa glycoprotein p(67) and its requirement in protein synthesis
Abstract
Eukaryotic initiation factor-2 (eIF-2) associated 67kDa polypeptide (p$\sp{67})$ plays a critical role in the regulation of protein synthesis initiation in mammalian cells. Under certain physiological conditions, phosphorylation of the $\alpha$-subunit of eIF-2 by kinases leads to eIF-2 inactivation and thereby protein synthesis inhibition. p$\sp{67}$ can protect the eIF-2 $\alpha$-subunit from inhibitory phosphorylation and therefore promotes the protein synthesis even in the presence of active eIF-2 kinases. p$\sp{67}$ level in the cells is regulated by two different mechanisms, (i) by activation of a p$\sp{67}$-deglycosylase. Heme-deficient reticulocyte and vaccinia viral infected animal cells use these mechanisms. (ii) at the mRNA level. This mechanism is used during serum starvation and mitogen stimulation of the cells. Direct demonstration and the requirement of p$\sp{67}$ in protein synthesis in vivo was done using cloned p$\sp{67}$ cDNA. The sense and antisense p$\sp{67}$ cDNA were expressed in rat-hepatoma (KRC-7) cells. These phenotypes were then used to investigate the function of p$\sp{67}$ gene in protein synthesis regulation. Expression of the antisense p$\sp{67}$ cDNA in the presence of zinc in PMA-induced serum starved cells completely inhibited induced appearance of p$\sp{67}$ mRNA, p$\sp{67}$ protein and subsequent protein synthesis. Also on expression of sense p$\sp{67}$ cDNA the appearance of p$\sp{67}$ mRNA in the serum starved cells was accompanied by the appearance of p$\sp{67}$ protein and hence the restoration of the rates of total protein synthesis. Thus the loss of p$\sp{67}$ mRNA in serum starved cells is due to loss of p$\sp{67}$ transcription and the p$\sp{67}$ transcription regulates total rate of protein synthesis. The eIF-2 kinase activity was the same in the cells grown in complete medium, after serum starvation and subsequent mitogen stimulation. It is not the level of eIF-2 kinase but the level of p$\sp{67}$ which changes the protein synthesis rate at different condition.
Subject Area
Biochemistry|Molecular biology
Recommended Citation
Gupta, Swati, "Regulation of an eukaryotic initiation factor-2 (eIF-2) associated 67 kDa glycoprotein p(67) and its requirement in protein synthesis" (1997). ETD collection for University of Nebraska-Lincoln. AAI9730272.
https://digitalcommons.unl.edu/dissertations/AAI9730272