EMBO Conference on Protein Synthesis and Translational Control

BARBARA GORGONI
133
Poster Abstracts
Multiple Poly(A)-Binding Proteins are essential for Xenopus laevis development
Nicola Gray 1, Barbara Gorgoni 2, William Richardson 2, Gavin Wilkie 2, Hannah Burgess 2,
Matthew Brook 2, Michael Sheets 3
1 Medical Research Council, United Kingdom
2 MRC-HRSU and University of Edinburgh, Germany
3 University of Wisconsin School of Medicine and Public Health, United States of America
Translation of specific mRNAs during gametogenesis and early embryogenesis is regulated by
alterations in poly(A) tail length. The function of poly(A) tails is mediated by a family of
poly(A)-binding proteins (PABPs). In Xenopus laevis, three cytoplasmic PABPs have been
described: PABP1, ePABP and ePABP2. Both PABP1 and ePABP stimulate translation while
ePABP2 is reminiscent of nuclear PABP. More recently our group identified a PABP that
segregates closely with mammalian PABP4 and that appears to be structurally and functionally
similar to PABP1 and ePABP. Interestingly, the different PABPs are expressed simultaneously
in several adult and embryonic tissues. This raises the fundamental question as to whether
they are functionally redundant or have individual roles.
To address this issue we have selectively knocked-down PABP1, ePABP and PABP4 in
Xenopus embryos, providing the first vertebrate PABP phenotypes. PABP1 and ePABP
morpholino-mediated knock-downs show severe early phenotypes, with defects in both
anterior and posterior structures, and are embryonic lethal. PABP4 morphants show a very
different phenotype that arises later during development and appears to affect only anterior
structures. These results reveal essential roles in development for each of the PABP proteins.
To further investigate the molecular basis of this specificity, we have compared the ability of
different PABPs to rescue the PABP1 phenotype. Our results support the hypothesis that
structurally similar PABP proteins have both overlapping and distinct roles in development.