The nuclear import factor p10 regulates the functional size of the nuclear pore complex during oogenesis.
Previtellogenic, stage-1 Xenopus oocytes produce mainly 5S and tRNA, whereas vitellogenic oocytes, stages 2-6, synthesize predominantly 18S and 28S rRNA. Using nucleoplasmin-coated gold as a transport substrate, it was determined that the shift in synthesis from small to large RNAs during oogenesis is accompanied by an increase in both the rates of signal-mediated nuclear import and the functional size of nuclear pores. It was observed that, despite the reduction in transport capacity, gold still accumulated at the cytoplasmic surface of the pores in stage-1 oocytes. This suggested that transport in these cells is limited by translocation factors, rather than by cytoplasmic binding factors. Analysis of extracts prepared from stage-1 and vitellogenic oocytes revealed that the transport factor p10 is more abundant in stage-1 cells. Microinjection of purified p10 into stage-2 oocytes reduced the nuclear import of large gold particles to the level observed in stage-1 cells. It is concluded that p10 can modulate transport through the pores by regulating the functional size of the central transporter element.
Feldherr
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Dept of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville, FL 32610, USA. feldherr@college.med.ufl.edu
Akin
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D
Moore
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MS
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002970:Cleavage Stage, Ovum / Q000187:drug effects; D017979:Gold Colloid / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D009685:Nuclear Envelope / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D056489:Nucleoplasmins; D009865:Oocytes / Q000378:metabolism; D009866:Oogenesis / Q000187:drug effects / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis; D020931:ran GTP-Binding Protein
D002352:Carrier Proteins; D017979:Gold Colloid; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D056489:Nucleoplasmins; D010750:Phosphoproteins; C089822:Ran-interacting protein p10, Xenopus; D029867:Xenopus Proteins; D020931:ran GTP-Binding Protein