Xenopus oocytes protein stability

The biochemical mechanism of Mos action is not yet established. Mos has been found to phosphorylate cyclin B in vitro, and it is possible that this phosphorylation directly inhibits cyclin B proteolysis (Roy et al., 1990). However, such a direct effect of phosphorylation on cyclin B stability remains to be demonstrated, and it is alternatively possible that Mos inhibits (directly or indirectly) the proteolytic pathway responsible for cyclin B degradation. Mos has recently been found to stimulate mitogen-activated protein kinase (MAP kinase) in Xenopus oocytes,... 

The Xenopus transcription factor IIIA not only acts as an essential RNA polymerase transcription factor for the expression of the 5S rRNA gene, it also binds to the 5S rRNA to form a 7S ribonucleoprotein particle that stabilizes the RNA until it is required for ribosome assembly and facilitates nuclear export of the 5S rRNA. Indeed, it was originally shown to be the protein component associated with 5S rRNA in the 7S particle in Xenopus oocytes before it was recognized as a transcription factor. How, we may ask, can this protein not only recognize specific DNA sequences in the 5S rRNA gene upstream region, but also recognize different, but equally specific, sequences in 5S rRNA ... 

Our current understanding of the transport, metabolism, and function of specific RNA molecules has been greatly facilitated by in vitro transcription systems that produce biochemical quantities of pure, radiolabeled or chemically modified RNA molecules. In this chapter we describe procedures that will enable investigators to synthesize specific RNAs, inject theseRNAs into Xenopus oocyte nuclei or cytoplasms, and determine their nucleocytoplasmic distribution, stability, protein associations, and covalent modifications. 

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