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Structural and biophysical characterization of murine rif1 C terminus reveals high specificity for DNA cruciform structures.

ABSTRACT: Mammalian Rif1 is a key regulator of DNA replication timing, double-stranded DNA break repair, and replication fork restart. Dissecting the molecular functions of Rif1 is essential to understand how it regulates such diverse processes. However, Rif1 is a large protein that lacks well defined functional domains and is predicted to be largely intrinsically disordered; these features have hampered recombinant expression of Rif1 and subsequent functional characterization. Here we applied ESPRIT (expression of soluble proteins by random incremental truncation), an in vitro evolution-like approach, to identify high yielding soluble fragments encompassing conserved regions I and II (CRI and CRII) at the C-terminal region of murine Rif1. NMR analysis showed CRI to be intrinsically disordered, whereas CRII is partially folded. CRII binds cruciform DNA with high selectivity and micromolar affinity and thus represents a functional DNA binding domain. Mutational analysis revealed an ?-helical region of CRII to be important for cruciform DNA binding and identified critical residues. Thus, we present the first structural study of the mammalian Rif1, identifying a domain that directly links its function to DNA binding. The high specificity of Rif1 for cruciform structures is significant given the role of this key protein in regulating origin firing and DNA repair.

SUBMITTER: Sukackaite R

PROVIDER: S-EPMC4022862 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Structural and biophysical characterization of murine rif1 C terminus reveals high specificity for DNA cruciform structures.

Sukackaite Rasa R Jensen Malene Ringkjøbing MR Mas Philippe J PJ Blackledge Martin M Buonomo Sara B SB Hart Darren J DJ

The Journal of biological chemistry 20140314 20

Mammalian Rif1 is a key regulator of DNA replication timing, double-stranded DNA break repair, and replication fork restart. Dissecting the molecular functions of Rif1 is essential to understand how it regulates such diverse processes. However, Rif1 is a large protein that lacks well defined functional domains and is predicted to be largely intrinsically disordered; these features have hampered recombinant expression of Rif1 and subsequent functional characterization. Here we applied ESPRIT (exp ...[more]

PMID: 24634216

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Project description:The spliceosome is a dynamic macromolecular machine that catalyzes the removal of introns from pre-mRNA to make mature message. Schizosaccharomyces pombe Cwf10 (homolog Saccharomyces cerevisiae Snu114 and of Human U5-116K), an integral member of the U5 snRNP, is a GTPase that shares sequence homology with the eukaryotic translation elongation factor EF2. Cwf10 is required for pre-mRNA splicing; however, its mechanism(s) of action is still not understood. Cwf10/Snu114 family members contain a conserved N-terminal extension (NTE) that lacks homology with EF2 and has been predicted to be an intrinsically unfolded domain. Using S. pombe as a model system, we show that the NTE is not essential, but cells lacking this domain are defective in pre-mRNA splicing at all temperatures. Genetic interactions between cwf10-M-NM-^TNTE and other pre-mRNA splicing mutants are consistent with a role for the NTE in spliceosome activation. Characterization of Cwf10-NTE by various biophysical techniques shows the NTE contains both regions of structure and disorder in solution. The first twenty-three highly-conserved amino acids of the NTE are essential for its role in splicing, but are not sufficient to restore pre-mRNA splicing to wild-type levels in cwf10-M-bM-^HM-^FNTE cells. When the NTE is overexpressed in the cwf10-M-NM-^TNTE background, it can complement the truncated Cwf10 protein in trans, and it also immunoprecipitates a complex similar in composition to the late-stage U5.U2/U6 spliceosome. These data show that the structurally flexible NTE is capable of making specific contacts within the spliceosome that may facilitate Cwf10M-bM-^@M-^Ys overall role facilitating spliceosome rearrangements. Interrogation of the S. pombe transcriptome using poly-A enriched RNA sequencing (Illumina HiSeq 2500) in wild type and cwf10-M-NM-^TNTE cultures. A total of 4 samples were analysed: two biological repeats of wild-type strain and two biological repeats of cwf10-M-NM-^TNTE

Dataset Information

Structural and biophysical characterization of murine rif1 C terminus reveals high specificity for DNA cruciform structures.

Publications

Structural and biophysical characterization of murine rif1 C terminus reveals high specificity for DNA cruciform structures.

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