Immunological evidence for the localization of a 110 kDa poly(A) binding protein from rat liver in nuclear envelopes and its phosphorylation by protein kinase C.
We have purified a 110 kDa poly(A) binding protein (P110) from rat liver which is thought to be involved in mRNA translocation through the nuclear pores and have demonstrated its localisation in the nuclear envelope using polyclonal antibodies and confocal laser scanning microscopy. Although P110 was prepared from highly purified nuclear envelopes, the polyclonal antibodies raised against them bind to nucleo- and cytoplasmic structures to a minor extent, but not to nucleolar structures. P110 decays spontaneously into several fragments which are also recognized by the polyclonal antibodies. The 110 kDa polypeptide and its fragments were phosphorylated by a nuclear envelope kinase and this phosphorylation was inhibited by a monoclonal antibody against protein kinase C and by a specific protein kinase C inhibitor obtained from bovine brain. Scatchard analysis was used to determine the influence of protein kinase C activators and inhibitors on nuclear envelope protein phosphorylation and RNA binding. The data indicate a close association between the RNA translocation machinery (the 110 kDa protein) and protein kinase C within the nuclear envelope. We suggest that the fragmentation of P110 is triggered before or during mRNA export and is not due to nonspecific proteolysis.
Schäfer
P
P
Institut für Biochemie der Johann Wolfgang Goethe-Universität Frankfurt, Germany.
Aitken
S J
SJ
Bachmann
M
M
Agutter
P S
PS
Müller
W E
WE
Prochnow
D
D
D000818:Animals; D002451:Cell Compartmentation; D002458:Cell Fractionation; D005455:Fluorescent Antibody Technique; D008099:Liver / Q000737:chemistry* / Q000378:metabolism; D008297:Male; D009685:Nuclear Envelope / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D039102:Poly(A)-Binding Proteins; D011493:Protein Kinase C / Q000302:isolation & purification* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D039102:Poly(A)-Binding Proteins; D016601:RNA-Binding Proteins; D011493:Protein Kinase C