Activities of cold-shock domain proteins in translation control

For efficient processing, transport, storage, translation, and degradation, stretches of RNA transcripts are required in a single-stranded conformatio n (ssRNA). A superfamily of OB-fold proteins is characterized by preference of binding to ssRNA. This superfamily consists of proteins containing eith er an S1 domain (S1-D) or a cold-shock domain (CSD). In a variety of situat ions, S1-D or CSD proteins are found in association with DEAD-box RNA helic ases and the two types of protein appear to function together to maintain r egions of ssRNA. CSD proteins are commonly found bound to stored (nontransl ating) mRNA, particularly during early development. Although complete remov al of the CSD proteins from mRNA permits its translation in vitro, low conc entrations of CSD protein on the mRNA may be required for maximal translati on efficiency in vivo. Another component of stored mRNP particles in Xenopu s oocytes is the protein kinase CK2, which phosphorylates the associated CS D proteins. It is argued here that the loading of CSD proteins on mRNA and the stability of the protein/mRNA complex are regulated by RNA helicase act ivity and protein phosphorylation. BioEssays 21:319-325, 1999. (C) 1999 Joh n Wiley & Sons, Inc.