THE ELAV-LIKE PROTEINS BIND TO AU-RICH ELEMENTS AND TO THE POLY(A) TAIL OF MESSENGER-RNA

The Elav-like proteins are specific mRNA binding proteins which are re quired for cellular differentiation. They contain three characteristic RNP2/RNP1-type RNA binding motifs. Previously we have shown that the first and second RNA binding domains bind to AU-rich elements in the 3 '-UTR of mRNA. In this paper we show that the Elav-like proteins exhib it poly(A) binding activity. This activity is distinct from poly(A) bi nding activities that have been previously described. The Elav-like pr oteins specifically bind to long chain poly(A) tails. We have shown th at the third RNA binding domain encompasses this poly(A) binding activ ity. Using poly(A)Sepharose beads in a 'sandwich' assay we have shown that the Elav-like proteins can bind simultaneously to the AU-rich ele ment and to the poly(A) tail.