Publication details
TDP-43 forms a functional dimer interface upon UG-rich RNA binding leading to aberrant CFTR exon 9 splicing
| Authors | |
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| Year of publication | 2017 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | Alternative premRNA splicing plays a key role in creating the vast number of gene products underlying our complex organism. Processing of premRNAs is tightly regulated and imbalances can change the outcome of gene expression often leading to disease. TAR DNAbinding protein (TDP43) inhibits splicing of exon 9 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which is associated with severe forms of cystic fibrosis. Mutations in the 3’ splice site (3’ss) of CFTR exon 9 causing extension of a UGrich region and polypyrimidine tract shortening, create a high affinity binding site for TDP43. Upon RNA binding, TDP43 recruits hnRNPA1 and thus formed complex prevents the recognition of the 3’ss of exon 9 by the spliceosomal machinery causing exon 9 skipping and subsequent production of a nonfunctional CFTR protein. Although RNA recognition and binding by TDP43 alone and in complex with other hnRNPs has numerous functional implications, molecular details of such interactions remained elusive. Our structural studies combined with biophysical approaches reveal that two copies of TDP43 create a new proteinprotein interface with a salt bridge upon binding to the extended UGrich sequence. Sitedirected mutagenesis of amino acids involved in salt bridge formation reveals the functional significance of the proteinprotein interface. Unexpectedly, mutations at the interaction site of the two TDP43 copies reduce exon 9 skipping almost to the same extent as completely abolishing UGrich RNA binding. Furthermore, this complex recruits two copies of hnRNP A1 to the 3’ss which blocks access of the canonical factor U2AF35 while U2AF65 binding is weakened because of polypyrimidine tract shortening. Thus TDP43 and hnRNP A1 form a network of functional RNAprotein and proteinprotein interactions which competes for the formation of the canonical splicing complex thereby driving CFTR exon 9 skipping |
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