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Molecular and Cellular Biology, September 2007, p. 6569-6579, Vol. 27, No. 18
0270-7306/07/$08.00+0     doi:10.1128/MCB.00881-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

An Interaction between Two RNA Binding Proteins, Nab2 and Pub1, Links mRNA Processing/Export and mRNA Stability ^,

Luciano H. Apponi,¹ Seth M. Kelly,² Michelle T. Harreman,^2, Alexander N. Lehner,^2, Anita H. Corbett,² and Sandro R. Valentini^1*

Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University, UNESP, Araraquara, SP 14801-902, Brazil,¹ Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322²

Received 18 May 2007/ Accepted 2 July 2007

mRNA stability is modulated by elements in the mRNA transcript and their cognate RNA binding proteins. Poly(U) binding protein 1 (Pub1) is a cytoplasmic Saccharomyces cerevisiae mRNA binding protein that stabilizes transcripts containing AU-rich elements (AREs) or stabilizer elements (STEs). In a yeast two-hybrid screen, we identified nuclear poly(A) binding protein 2 (Nab2) as being a Pub1-interacting protein. Nab2 is an essential nucleocytoplasmic shuttling mRNA binding protein that regulates poly(A) tail length and mRNA export. The interaction between Pub1 and Nab2 was confirmed by copurification and in vitro binding assays. The interaction is mediated by the Nab2 zinc finger domain. Analysis of the functional link between these proteins reveals that Nab2, like Pub1, can modulate the stability of specific mRNA transcripts. The half-life of the RPS16B transcript, an ARE-like sequence-containing Pub1 target, is decreased in both nab2-1 and nab2-67 mutants. In contrast, GCN4, an STE-containing Pub1 target, is not affected. Similar results were obtained for other ARE- and STE-containing Pub1 target transcripts. Further analysis reveals that the ARE-like sequence is necessary for Nab2-mediated transcript stabilization. These results suggest that Nab2 functions together with Pub1 to modulate mRNA stability and strengthen a model where nuclear events are coupled to the control of mRNA turnover in the cytoplasm.

Published ahead of print on 16 July 2007.

Supplemental material for this article may be found at http://mcb.asm.org/.

Present address: Cancer Research UK London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Hertfordshire EN6 3LD, United Kingdom.

Present address: University of Northampton, Park Campus, Northampton, Northamptonshire NN2 7AL, United Kingdom.