Crystallization of auto-regulatory A-rich repeats found in the 5'-UTR of human PABP mRNA.

Abstract

Eukaryotic poly(A)-binding protein (PABP) binds not only to the 3' poly(A) tail of most mRNAs, but also to the 5'-untranslated region (UTR). The latter form of binding leads to auto-regulation of PABP expression. The 5'-UTR sequence contains A-rich repeats different from that in 3'-UTR. The role of these A-rich repeats in auto-regulation, however, remains unknown. To confirm that the 5'-UTR sequence has a specific structure before or after PABP binding, and to determine the function of such structure, several RNA/DNA fragments containing A-rich repeats were examined by crystallization, fluorescence microscopy and X-ray diffraction. Crystals were obtained for several of these fragments. In particular, single crystals were obtained for the DNA fragment with four repeats, suggesting that such fragment is folded into a regular structure through A:A interactions.