Nucleic Acids Research, 1981, Vol. 9, No. 3 605-621
© 1981
MOLECULAR BIOLOGY |
Analysis and reconstruction of an RNP particle which stores 5S RNA and tRNA in amphibianoocytes
Department of Zoology, University of St. Andrews St. Andrews, Fife KY16 9TS, UK
Received October 31, 1980. Previtellogenic oocytes of Triturus cristatus accumulate a free cyto-plasmic RNP which sediments at 40S and contains 5S RNA and tRNA in associ-ation with two proteins of MW 45,000 and 59,0C0 daltons (P45 and P39). The40S particle has a buoyant density of 1.53 g.cm–3in CsCl and consists offour identical RNP subunits. Each monomeric subunit contains one moleculeof 5S RNA, three molecules of tRNA, two molecules of P45 and one moleculeof P39. The 40S particle can be completely dissociated by SDS treatmentinto its individual components, and the subunits, and even the complete40S particle, can be reformed by removal of SDS in the presence of 0.2 MNaCl. RNA/protein binding experiments with isolated components., andanalysis of reformed RNP complexes in CsCl gradients, demonstrate that thestable interactions are: 5S RNA/P45, 3(tRNA)/P45, 5S RNA/P39 and 5SRNA/P45/P39. Imnunological studies show that P45 has also a nuclear loca-tion and may bind to the 5S RNA transcript ir. the chromatin, whereas P39is predominantly cytoplasmic and is possibly related to proteins associatedwith 5S RNA in the ribosomal 60S subunit. It is suggested that the 40SRNP particle not only stores 5S RNA and tRNA but also provides a means forthe exchange of the 5S RNA transcript binding protein (P45) for the 5S RNAribosome associated protein (P39).INTRODUCTIONMany of