scholarly journals The enzymic properties of rat-liver nuclei. 1. Estimation of the extent to which contaminant material contributes to the activity observed in the nuclear fraction

1956 ◽  
Vol 64 (2) ◽  
pp. 361-368 ◽  
Author(s):  
D. B. Roodyn
1968 ◽  
Vol 37 (1) ◽  
pp. 163-181 ◽  
Author(s):  
Paul D. Sadowski ◽  
Janet Alcock Howden

Isolated rat liver nuclei were washed with Triton-X-100 in the presence of liver cell sap. This treatment liberated a fraction of polysomes which were isolated by differential centrifugation and were designated "outer membrane polysomes." The outer membrane polysomes synthesized protein in vivo. Shortly after injection of orotic acid-14C, the RNA of outer membrane polysomes had a higher specific activity than that of cytoplasmic polysomes. It was postulated that outer membrane polysomes may be an intermediate in the transfer of newly synthesized RNA from the nucleus to the cytoplasm. In other experiments, Triton-washed rat liver nuclei were lysed in the presence of deoxycholate and deoxyribonuclease. A ribonucleoprotein fraction was isolated from the lysate by differential centrifugation. This fraction contained "intranuclear ribosomes," which sedimented like partially degraded polysomes in sucrose gradients. This degradation could be partially prevented if intranuclear ribosomes were purified by sedimentation through heavy sucrose. The resulting pellets were termed "intranuclear polysomes" because they contained some undergraded polysomes. Intranuclear polysomes were highly radioactive after a brief pulse with orotic acid-14C, but did not appear to synthesize protein rapidly in vivo. Intranuclear polysomes may represent the initial stage of assembly of polyribosomes in the nucleus.


1973 ◽  
Vol 248 (21) ◽  
pp. 7595-7600
Author(s):  
Edward M. Johnson ◽  
Giorgio Vidali ◽  
Virginia C. Littau ◽  
Vincent G. Allfrey

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