Funding Organization(s): FAPERJ, Brazilian National Council for Scientific and Technological Development (CNPq), Brown University Brazil Initiative Colaboration Grant
Experimental Data Snapshot
Method: SOLUTION NMR
Conformers Calculated: 400
Conformers Submitted: 20
Selection Criteria: structures with the lowest energy
Human antigen R (HuR) functions as a major post-transcriptional regulator of gene expression through its RNA-binding activity. HuR is composed by three RNA recognition motifs, namely RRM1, RRM2, and RRM3. The two N-terminal RRM domains are disposed in tandem and contribute mostly to HuR interaction with adenine and uracil-rich elements (ARE) in mRNA ...
Human antigen R (HuR) functions as a major post-transcriptional regulator of gene expression through its RNA-binding activity. HuR is composed by three RNA recognition motifs, namely RRM1, RRM2, and RRM3. The two N-terminal RRM domains are disposed in tandem and contribute mostly to HuR interaction with adenine and uracil-rich elements (ARE) in mRNA. Here, we used a combination of NMR and electrospray ionization-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS) to characterize the structure, dynamics, RNA recognition, and dimerization of HuR RRM1. Our solution structure reveals a canonical RRM fold containing a 19-residue, intrinsically disordered N-terminal extension, which is not involved in RNA binding. NMR titration results confirm the primary RNA-binding site to the two central β-strands, β1 and β3, for a cyclooxygenase 2 (Cox2) ARE I-derived, 7-nucleotide RNA ligand. We show by 15 N relaxation that, in addition to the N- and C-termini, the β2-β3 loop undergoes fast backbone dynamics (ps-ns) both in the free and RNA-bound state, indicating that no structural ordering happens upon RNA interaction. ESI-IMS-MS reveals that HuR RRM1 dimerizes, however dimer population represents a minority. Dimerization occurs via the α-helical surface, which is oppositely orientated to the RNA-binding β-sheet. By using a DNA analog of the Cox2 ARE I, we show that DNA binding stabilizes HuR RRM1 monomer and shifts the monomer-dimer equilibrium toward the monomeric species. Altogether, our results deepen the current understanding of the mechanism of RNA recognition employed by HuR.
Related Citations:
(1)H, (15)N and (13)C resonance assignments of the RRM1 domain of the key post-transcriptional regulator HuR. Mujo, A., Lixa, C., Carneiro, L.A., Anobom, C.D., Almeida, F.C., Pinheiro, A.S. (2015) Biomol NMR Assign 9: 281
Organizational Affiliation:
Department of Biochemistry, Institute of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, 21941-909, Brazil. pinheiro@iq.ufrj.br.
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