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Title: RNA 3' cleavage and polyadenylation in oocytes, eggs and embryos of Xenopus laevis
Author: Chambers, Alistair
ISNI:       0000 0001 3526 2623
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1986
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The general mechanism used to make the 3' ends of eukaryotic mRNAs involves 3' cleavage of a precursor mRNA followed by the addition of a poly - A tail to the newly formed mRNA 3' end. The 3' ends of histone mRNAs are generated by a 3' cleavage reaction but these mRNAs are usually not polyadenylated. An exception to this rule is in the Xenopus oocyte where polyadenylated histone transcripts do exist. These adenylated histone transcripts become de - adenylated as the oocyte matures into an egg. Changes in the rate of histone protein translation also occur during Xenopus development, with increases in the translation rate in the egg over the oocyte and in the embryo over the egg. This thesis describes experiments in which histone precursor mRNAs, made in vitro, were injected into oocytes, eggs and embryos to determine whether 3' cleavage of precursor mRNAs also varied during early development. It was confirmed that histone precursor mRNA was accurately and efficiently 3' cleaved after injection into the oocyte nucleus. Accurate but less efficient 3' cleavage occurred on injection of histone precursor mRNAs into eggs and embryos. A polyadenylation activity was discovered in eggs and embryos which added an A tail directly to the 3' ends of injected precursor mRNAs. Experiments to investigate this polyadenylation activity were performed. The significance of the observed histone 3' processing activities is discussed in relation to possible mechanisms for the increase in translation of histone proteins during early development. Experiments using the oocyte as an assay system, to investigate 3' end formation of polyadenylated mRNAs, were also performed. In DNA injection experiments the oocyte was shown to correctly generate the mouse β globin mRNA 3' end. In injection experiments using artificial precursor mRNAs to both mouse globin and Xenopus heat shock mRNAs no 3' cleavage was detected.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry ; QL Zoology ; QP Physiology