Interconversion of Drosophila nuclear lamin isoforms during oogenesis, early embryogenesis, and upon entry of cultured cells into mitosis.
Two isoforms of a single nuclear lamin, distinguishable on one-dimensional SDS-polyacrylamide gels, have previously been identified in Drosophila nuclei during interphase. A third species, designated lamin Dmmit, has now been identified as soluble in extracts of Drosophila tissue culture cells blocked in mitosis by drugs. An apparently identical form is the only lamin species detectable in late-stage egg chambers and early embryos. Phosphoamino acid analyses suggest that the conversion of lamins Dm1 and Dm2 to lamin Dmmit is brought about by a specific rearrangement of phosphate groups rather than by dramatic net changes in the levels of lamin phosphorylation. The residues involved in these phosphorylation/dephosphorylation reactions have been tentatively mapped to a 17.8-kD cyanogen bromide fragment containing amino acids 385-547. This represents a potential "hinge" domain in the lamin structure between the end of coil 2 and the globular COOH terminus. These results have implications for understanding the regulation of nuclear envelope breakdown during mitosis and karyoskeletal dynamics during oogenesis and early embryogenesis.
Smith
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Department of Pharmacological Sciences, State University of New York, Stony Brook 11794-8651.
Fisher
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D000818:Animals; D003488:Cyanogen Bromide; D004331:Drosophila melanogaster / Q000196:embryology / Q000378:metabolism* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D007399:Interphase; D034882:Lamins; D008938:Mitosis; D009685:Nuclear Envelope / Q000502:physiology / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism / Q000648:ultrastructure; D009866:Oogenesis; D010446:Peptide Fragments / Q000032:analysis; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis
D034882:Lamins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010710:Phosphates; D010769:Phosphothreonine; D010768:Phosphoserine; D003488:Cyanogen Bromide