The rate of protein synthesis in mammals is largely regulated by phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2) that is modulated by the cellular glycoprotein, p67, due to its protection of eIF2α phosphorylation (POEP) activity. At the N-terminus of p67, there are three unique domains, and at the C-terminus there is a conserved acid sequence. To analyze the importance of these domains, C-terminal deletion mutants of rat p67 were expressed constitutively in KRC-7 cells. In these cells, the phosphorylation level of the α-subunit of eIF2 was determined, and it was found that expression of the 1-97 amino acid segment of rat p67 increases POEP activity in vivo, and induces the endogenous levels of p67. These cells also show increased growth rate, and efficient translation of chloramphenicol acetyltransferase and β-galactosidase reporter genes. At the N-terminus of p67, there are two unique domains: a lysine-rich domain I with the sequence 36KKKRRKKKK44, and an acidic residue-rich domain with the sequence 77EEKEKDDDDEDGDGD91. Substitution of lysine-rich domain I with 36NMKSGNKTQ44 in rat recombinant p67 resulted in the inhibition of its POEP activity, and substitution of the acidic residue-rich domain with 77QNIQKALEPEAGDGA91, resulted in no inhibition of POEP activity in KRC-7 cells. Taken together, our data suggest that protection of translation initiation factor eIF2 phosphorylation correlates with eIF2-associated glycoprotein p67 levels and requires the lysine-rich domain I of p67.
- Glycoprotein p67
- Protection of eIF2α phosphorylation (POEP)
- Translation initiation factor eIF2
ASJC Scopus subject areas