RNA localisation in the Xenopus oocyte. (360G-Wellcome-084169_Z_07_Z)

The development of the early embryo depends on the polarisation of the egg and an important component of this is the localisation of mRNAs that determine cell fate. In vertebrates the Xenopus oocyte has been particularly productive in understanding RNA localisation, which has been ascribed to several kinds of simple repeated sequences found in the 3 UTRs of localised mRNAs. These direct RNAs either to the germ plasm, which controls germ line development, or to the wider vegetal cortex, where th ey control early embryonic patterning (these are early and late pathways). Exactly how this is achieved is only partially understood. We have made preliminary quite unexpected and novel observations that localisation to germ plasm can be achieved in late oogenesis and involves co-operation between 3 UTRs and previously unsuspected 5 sequences. These interactions may be intermolecular, suggesting they are the basis of mRNP particle building. We will define the 5 localisation sequences in s everal mRNAs and establish the nature of their interactions with 3 sequences. The role of these sequences and their interactions in building mRNP particles will be studied, and the proteins that bind to them will be identified.