A 60‐kDa protein from rabbit reticulocytes specifically recognizes the capped 5′ end of β‐globin mRNA

Abstract

The binding of proteins from rabbit reticulocyte lysate to in‐vitro‐generated β‐globin mRNA and its defined segments was investigated using ultraviolet‐cross‐linking experiments as well as gel‐retardation assays. Under stringent conditions, only three proteins (72, 60 and 50 kDa) were found associated with full‐length β‐globin mRNA at different positions. The 72‐kDa protein is most likely the poly(A)‐binding protein and binds, as expected, to the poly(A) tail, whereas the 50‐kDa protein exhibits affinity for the trailer region of β‐globin mRNA. The binding region of the 60‐kDa protein is located at the 5′ end of β‐globin mRNA. The interaction of this protein is dependent on the presence of the 5′ cap structure, as indicated by competition experiments using an uncapped β‐globin‐mRNA leader segment. Further competition experiments with β‐globin mRNA, deleted in part in the leader region, suggest that, besides the cap structure, certain sequence elements are necessary for the interaction of the 60‐kDa protein and the β‐globin mRNA leader. Copyright © 1991, Wiley Blackwell. All rights reserved