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Recognition of GU‐rich polyadenylation regulatory elements by human CstF‐64 protein
Author(s) -
Pérez Cañadillas José Manuel,
Varani Gabriele
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg259
Subject(s) - polyadenylation , biology , cleavage stimulation factor , cleavage and polyadenylation specificity factor , rna binding protein , rna , protein subunit , microbiology and biotechnology , plasma protein binding , binding site , heterotrimeric g protein , genetics , signal transduction , gene , g protein
Vertebrate polyadenylation sites are identified by the AAUAAA signal and by GU‐rich sequences downstream of the cleavage site. These are recognized by a heterotrimeric protein complex (CstF) through its 64 kDa subunit (CstF‐64); the strength of this interaction affects the efficiency of poly(A) site utilization. We present the structure of the RNA‐binding domain of CstF‐64 containing an RNA recognition motif (RRM) augmented by N‐ and C‐terminal helices. The C‐terminal helix unfolds upon RNA binding and extends into the hinge domain where interactions with factors responsible for assembly of the polyadenylation complex occur. We propose that this conformational change initiates assembly. Consecutive Us are required for a strong CstF–GU interaction and we show how UU dinucleotides are recognized. Contacts outside the UU pocket fine tune the protein–RNA interaction and provide different affinities for distinct GU‐rich elements. The protein–RNA interface remains mobile, most likely a requirement to bind many GU‐rich sequences and yet discriminate against other RNAs. The structural distinction between sequences that form stable and unstable complexes provides an operational distinction between weakly and strongly processed poly(A) sites.