Complex structure of the C-terminal RNA-binding domain of hnRNP D(AUF1) with telomeric DNA
[HNRPD_HUMAN] Binds with high affinity to RNA molecules that contain AU-rich elements (AREs) found within the 3'-UTR of many proto-oncogenes and cytokine mRNAs. Also binds to double- and single-stranded DNA sequences in a specific manner and functions a transcription factor. Each of the RNA-binding domains specifically can bind solely to a single-stranded non-monotonous 5'-UUAG-3' sequence and also weaker to the single-stranded 5'-TTAGGG-3' telomeric DNA repeat. Binds RNA oligonucleotides with 5'-UUAGGG-3' repeats more tightly than the telomeric single-stranded DNA 5'-TTAGGG-3' repeats. Binding of RRM1 to DNA inhibits the formation of DNA quadruplex structure which may play a role in telomere elongation. May be involved in translationally coupled mRNA turnover. Implicated with other RNA-binding proteins in the cytoplasmic deadenylation/translational and decay interplay of the FOS mRNA mediated by the major coding-region determinant of instability (mCRD) domain. 
Publication Abstract from PubMed
Heterogeneous nuclear ribonucleoprotein D, also known as AUF1, has two DNA/RNA-binding domains, each of which can specifically bind to single-stranded d(TTAGGG)n, the human telomeric repeat. Here, the structure of the C-terminal-binding domain (BD2) complexed with single-stranded d(TTAGGG) determined by NMR is presented. The structure has revealed that each residue of the d(TAG) segment is recognized by BD2 in a base-specific manner. The interactions deduced from the structure have been confirmed by gel retardation experiments with mutant BD2 and DNA. It is known that single-stranded DNA with the telomeric repeat tends to form a quadruplex and that the quadruplex has an inhibitory effect on telomere elongation by telomerase. This time it is revealed that BD2 unfolds the quadruplex of such DNA upon binding. Moreover, the effect of BD2 on the elongation by telomerase was examined in vitro. These results suggest the possible involvement of heterogeneous nuclear ribonucleoprotein D in maintenance of the telomere 3'-overhang either through protection of a single-stranded DNA or destabilization of the potentially deleterious quadruplex structure for the elongation by telomerase.
Structure of hnRNP D complexed with single-stranded telomere DNA and unfolding of the quadruplex by heterogeneous nuclear ribonucleoprotein D.,Enokizono Y, Konishi Y, Nagata K, Ouhashi K, Uesugi S, Ishikawa F, Katahira M J Biol Chem. 2005 May 13;280(19):18862-70. Epub 2005 Feb 24. PMID:15734733
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.