title: Active transport of messenger ribonucleoprotein particles in a reconstituted cell-free system.
abstract: The ability of a reconstituted cell-free system to transport mRNA as a ribonucleoprotein particle has been examined. Poly(A) messenger ribonucleoproteins (mRNPs), UV cross-linked after release from isolated liver nuclei in a cell-free system, exhibited a buoyant density of 1.33 g/cm3 in cesium sulfate and 1.47 g/cm3 in cesium chloride, values identical to those of poly(A) mRNP isolated directly from liver polysomes. Furthermore, the in vivo and in vitro transported mRNP showed a similar degree of resistance to RNase digestion and had sedimentation coefficients approximately 2.5 times that of the isolated mRNA. Release of both total mRNA and alpha 2 mu-globulin mRNA was proportional to the concentration of a specific cytoplasmic protein. Removal of the transport proteins from the cytosol with streptomycin sulfate provided a basal system incapable of supporting the active transport of alpha 2 mu-globulin mRNA. Hybridization of released RNA with a recombinant probe specific for intron 6 of alpha 2 mu-globulin showed that intron sequences were retained within the nucleus under optimal alpha 2 mu-globulin mRNA transport conditions and that the transported alpha 2 mu-globulin mRNA was of mature size.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000510:Alpha-Globulins / Q000235:genetics; D000818:Animals; D001693:Biological Transport, Active; D002474:Cell-Free System; D008099:Liver / Q000032:analysis; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D012261:Ribonucleoproteins / Q000378:metabolism*
chemical_list: D000510:Alpha-Globulins; D012333:RNA, Messenger; D012261:Ribonucleoproteins; C013803:alpha 2u globulin; C026452:messenger ribonucleoprotein; D000255:Adenosine Triphosphate