The role of the cytosolic fraction and of initiation factor eIF-2 for changes of the rate of protein synthesis during liver regeneration.
The protein synthesis-stimulating activity of the cytosolic fraction from regenerating rat liver was tested in a cell-free system using washed polysomes from normal rat liver. This activity undergoes significant changes during liver regeneration after partial hepatectomy (p.h.). An initial decrease until 16 h after p.h. is followed by a significant increase until 24 h after p.h. Beyond 32 h after p.h. the activity begins to decline again. Evidence is presented that these changes of the cytosolic activity may not be due to alterations in the distribution of protein synthesis-stimulating factors between the microsomal and the cytosolic fraction. The Met-tRNAf-binding activity of the cytosolic fraction changes during liver regeneration analogously to the protein synthesis-stimulating activity measured in the polysomal assay. This indicates that initiation factor eIF-2 is involved in the observed changes of the cytosolic activity. This conclusion could be confirmed by addition of purified eIF-2 to the polysomal assay system. Addition of eIF-2 to cytosolic fractions of low endogenous protein synthesis-stimulating activity (16 h after p.h.) enhances amino-acid incorporation to a significantly higher extent than addition to highly active cytosolic fractions (24 h and 32 h after p.h.). From these results it is concluded that changes in eIF-2 plays an essential role in the described alterations of the cytosolic activities during liver regeneration.
D000818:Animals; D002474:Cell-Free System; D003600:Cytosol / Q000502:physiology*; D015852:Eukaryotic Initiation Factor-2; D007700:Kinetics; D008115:Liver Regeneration; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000502:physiology*; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000502:physiology*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D015852:Eukaryotic Initiation Factor-2; D010448:Peptide Initiation Factors; D011506:Proteins; D012346:RNA, Transfer, Amino Acyl; C026464:tRNA(m)(Met), methionine-