S-phase phosphorylation of lamin B2.
Lamin B2 modification in synchronously dividing populations of human diploid fibroblasts was determined by 2-dimensional gel electrophoresis and [32P]orthophosphate labelling. In quiescent (G0) and G1 cultures of HDF, lamin B2 migrated as 2 spots on 2-dimensional gels. In contrast, in S-phase populations of HDF lamin B2 migrated as a single basic species. The level of lamin B2 phosphorylation was determined after immunoisolation from [32P]orthophosphate labelled cells. The results of these experiments indicated a 2-3-fold increase in the steady state level of lamin B2 phosphorylation in S-phase HDF compared with G0 HDF. Consistent with this evidence, tryptic peptide maps revealed the presence of a phosphopeptide in S-phase lamin B2 which was absent from G0 lamin B2. Since all of the phosphate incorporated into S-phase and G0 lamin B2 was recovered in serine residues we conclude that the S-phase specific phosphopeptide did not represent either of the cdc2 sites associated with entry nuclear lamina breakdown.
Kill
I R
IR
Department of Biological Sciences, University of Dundee, Scotland, UK.
Hutchison
C J
CJ
D015153:Blotting, Western; D002460:Cell Line; D015180:Electrophoresis, Gel, Two-Dimensional; D005347:Fibroblasts / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D034921:Lamin Type B; D034882:Lamins; D009687:Nuclear Proteins / Q000378:metabolism*; D010449:Peptide Mapping; D010710:Phosphates / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D016196:S Phase; D014357:Trypsin / Q000378:metabolism
D034921:Lamin Type B; D034882:Lamins; D009687:Nuclear Proteins; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D014357:Trypsin