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Lamella-localized ZBP1 (white) granules do not form if ZBP1 cannot bind actin mRNA (right).

On page 77, Farina et al. get a handle on RNA localization machinery by proving that an RNA-binding protein is essential for both mRNA transport and cell motility.

The cell motility connection comes about because localization of the ß-actin mRNA to the lamellae is required for cell polarity and motility in fibroblasts. The new results show that this localization depends on ZBP1, a protein associated with cytoplasmic granules that contain the actin mRNA. ZBP1 bound to the mRNA through two COOH-terminal KH domains that were required for granule formation and attachment to the actin cytoskeleton. NH₂-terminal regions of ZBP1 were necessary for granule localization in the lamellae.

Dominant–negative ZBP1 constructs that mislocalized actin RNA inhibited fibroblast motility. Since mRNAs for some actin-associated proteins, such as ARP3, also contain ZBP1-binding sequences, the authors believe that ZBP1 may link several messages involved in motility to a transport complex. But ZBP1 may be more than just a scaffold: a ZBP1 homologue has been linked to translational repression of the insulin-related growth factor. Perhaps ZBP1 also ensures that the actin mRNA is not translated until it reaches its ultimate destination.The group plans to purify ZBP1- associated proteins in the complex to identify the motor responsible for actin-based transport. ZBP1 is also known to be associated with microtubules in neurons, so it may connect to different motors depending on the cell type.

Nicole LeBrasseur

lebrasn{at}rockefeller.edu

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Two ZBP1 KH domains facilitate ß-actin mRNA localization, granule formation, and cytoskeletal attachment

Kim L. Farina, Stefan Hüttelmaier, Kiran Musunuru, Robert Darnell, and Robert H. Singer
J. Cell Biol. 2003 160: 77-87. [Abstract] [Full Text] [PDF]

This Article PDF (Full Text) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by LeBrasseur, N. Search for Related Content PubMed Articles by LeBrasseur, N. Related Collections Related Article Social Bookmarking                      What's this?