Differential transport and integration into the nuclear lamina for lamins A, B, and C.
Lamins A, B, and C are the major proteins of the mammalian nuclear lamina and have been well studied in BHK-21 cells. Using in vivo labelling, cell fractionation, and immunoprecipitation, we have found that lamins have different patterns of nuclear transport and solubility. Newly synthesized lamin A is translocated to the nucleus faster than lamin C or B. It is the most tightly bound lamin and cannot be extracted from the lamina by nonionic detergent or high-salt buffers. Lamins B and C migrate more slowly to the nucleus. Partitioning between cytoskeleton and detergent-soluble fractions shows that integration of lamins B and C is not completed before a 1-h chase. For lamin C this process is dependent upon protein synthesis and can be inhibited with cycloheximide. Even though lamins A and C are almost identical, lamin C is never firmly bound to the lamina and can be partially solubilized upon high-salt treatment.
Institut du cancer de Montréal, Qué., Canada.
A
A
Dagenais
A
A
LeMyre
V
V
Bibor-Hardy
D000818:Animals; D001692:Biological Transport; D002458:Cell Fractionation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D003902:Detergents; D007163:Immunosorbent Techniques; D007668:Kidney; D007700:Kinetics; D034904:Lamin Type A; D034882:Lamins; D009687:Nuclear Proteins / Q000378:metabolism*; D012995:Solubility
D003902:Detergents; D034904:Lamin Type A; D034882:Lamins; D009687:Nuclear Proteins; C440308:lamin C