The role of the poly(A)-specific ribonuclease (PARN) in mRNA decay

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Degradation of the poly(A) tail (deadenylation) is the first and rate-limiting step in the decay of many mRNAs. Deadenylation is also used as a means of translational control during oocyte maturation and early development. We have purified and cloned a poly(A)-specific 3'-exoribonuclease (PARN) that is responsible for deadenylation in oocytes and possible also in somatic cells. Surprisingly, the nuclease prefers substrate RNAs carrying a 5' cap. The current application has three goals: First, overproduction of sufficient quantities of PARN in a eukaryotic system to allow a characterisation of the enzyme's functional properties, in particular cap dependence and processivity; second, the investigation of the relationship between mRNA translation and decay; and, third, the generation of a knock-out mouse to obtain definitive evidence regarding the physiological role of PARN.