A study of changes in the subcellular distribution of 4S and5S RNA during oogenesis revealed that in previtellogenic oocytes most 4 and 5S RNA is stored in 42S RNP particles. Accumulation between previtellogenic and white stages is mainly in the soluble fraction, the amount in 42S particles remaining relatively constant. The 42S 4S plus 5S RNA is released between white and full grown stages. Ribosome bound 5$ RNA increases four fold and the soluble non ribosome bound pool decreases although 20% of the total remains there. Over 90% of the 4S RNA is located in the full grown oocyte soluble fraction. The hypothesis that during oogenesis changes in the population of tRNA may control the relative translational efficiency of various mRNAs and that sequestration in 42S RNPs may enable the populations to be kept separate early in oogenesis was tested by cell free translation. No supportive evidence was found. Using two dimensional gel analysis several control systems were found to operate over protein synthesis during oogenesis. Subcellular fractionation enabled identification of four protein classes (soluble, ribosomal, 42S particle and mRNP particle) which are under separate control. Although synthesis of the majority of acidic and neutral proteins (most of which probably fall into the soluble class), was constant throughout oogenesis some proteins which increase or decrease in relative synthesis as well as some detectable only at certain stages were identified. Changes in relative synthesis may occur mainly between previtellogenic and white or white and full grown stages or more gradually over the course of oogenesis. A comparison of protein synthesis in previtellogenic oocytes of Xenopus laevis and Xenopus borealis revealed a number of interspecies differences in electrophoretic mobility of proteins which would be useful markers if a heterologous system was used to study control of protein synthesis during oogenesis.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649572 |
| Date | January 1978 |
| Creators | Dixon, Linda Kathleen |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13657 |
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