Disease relevance of RRM2

• Our findings confirm the importance of RRM2 in pancreatic adenocarcinoma gemcitabine chemoresistance [1].
• Synergism between RRM2 siRNA and gemcitabine results in markedly suppressed tumor growth, increased tumor apoptosis and inhibition of metastasis [1].
• The conserved linkage group consisting of the RRM2, ODC1, P5, and N-myc in the hamster and human genomes prompted our investigation of human neuroblastomas [2].
• Stable suppression of the R2 subunit of ribonucleotide reductase by R2-targeted short interference RNA sensitizes p53(-/-) HCT-116 colon cancer cells to DNA-damaging agents and ribonucleotide reductase inhibitors [3].
• Development of resistance to hydroxyurea during treatment of human myelogenous leukemia K562 cells with alpha-difluoromethylornithine as a result of coamplification of genes for ornithine decarboxylase and ribonucleotide reductase R2 subunit [4].

Psychiatry related information on RRM2

• The differential equation consisting of two parallel reactions was solved to predict the concentration of RR2 at any reaction time with very good agreements [5].

High impact information on RRM2

• Expression of p53R2, but not R2, was induced by ultraviolet and gamma-irradiation and adriamycin treatment in a wild-type p53-dependent manner [6].
• It is composed of two different dimeric proteins R1 and R2 (refs 3-5) [7].
• Iron-free R2, apoR2, is a precursor of active R2 and folds into a stable protein which is transformed into active R2 by ferrous ions and molecular oxygen [7].
• R2 subunits contain buried iron-centres with each centre formed by two ferric ions coordinated by four carboxylates and two histidine ligands [7].
• We also show that RRM2 of SF2/ASF plays an important role in alternative splicing specificity: deletion of this domain results in a protein that, although active in alternative splicing, has altered specificity in 5' splice site selection [8].

Chemical compound and disease context of RRM2

• In order to assess target down-regulation by GTI-2040, RRM2 mRNA expression levels were analyzed in pre- and post-treatment samples from a phase II clinical trial of GTI-2040 combined with capecitabine in patients with metastatic breast cancer [9].
• TNFalpha, R1 and R2 serum levels measured in MS patients did not differ from those measured in healthy individuals and did not correlate with (a) clinical relapses, (b) presence of gadolinium-enhancing brain-magnetic resonance imaging (MRI) lesions, and (c) bioactivity of TNFalpha [10].
• These results bear a strong resemblance to the spectra of Escherichia coli ribonucleotide reductase (R2), and density functional theory calculations were conducted on the W48F/D84E R2 mutant in order to determine the energetics of formation of a monodentate end-on-bound O2 to one iron in the binuclear site [11].
• RESULTS: Circulating adiponectin was negatively associated, whereas AdipoR1/R2 mRNA levels were positively associated with obesity, glucose and lipid levels, and insulin resistance [12].
• BACKGROUND: This study of GTI-2040, a 20-mer phosphorothioate oligonucleotide complementary to the messenger ribonucleic acid (mRNA) of the R2 subunit of ribonucleotide reductase (RNR), was conducted to determine the dose-limiting toxicity (DLT) and maximum-tolerated dose (MTD) of the agent in patients with advanced solid tumors or lymphoma [13].

Biological context of RRM2

• The nucleotide metabolism enzyme ribonucleotide reductase is composed of a regulatory subunit (RRM1) and a catalytic subunit (RRM2) [14].
• The modular protein harbors a N-terminal RNA recognition motif (RRM), RRM1, and in the C-terminal domain, a second, atypical RRM2, in addition to a phosphorylation site, and a putative nucleotide binding site [15].
• Here we show that RRM2 overexpression is associated with gemcitabine chemoresistance in pancreatic adenocarcinoma cells, and that suppression of RRM2 expression using RNA interference mediated by small interfering RNA (siRNA) enhances gemcitabine-induced cytotoxicity in vitro [1].
• Point mutations in RRM1 or RRM2 decreased the Kd for apo-B mRNA by two orders of magnitude whereas mutations in RRM3 reduced binding affinity 13-fold [16].
• Thus, we conclude that mouse chromosome 12 carries the functional locus for RRM2 [17].

Anatomical context of RRM2

• No significant change in the expression of RRM2 was observed in either cell line, although both gemcitabine-resistant cell lines had an approximate 3-fold increase in p53R2 protein [18].
• In contrast, hRRM2 was up-regulated by UV in both PC3 cells and KB cells. hRRM2 and p53R2 mRNA levels were assessed by Northern blot, and the results paralleled that of the Western blot [19].
• These results indicated that DNA damage resulted in elevated levels of the R2 protein and dNTPs and, consequently, enhanced the survival of p53(-/-) HCT-116 cells [3].
• By analysis of their electron paramagnetic resonance spectra, an increased level of the R2 protein was observed in the K562-DFMOr cells as compared to the wild type K562 cells [4].
• Previously, we have demonstrated that, among the three RRMs of La protein, the RRM2 interacts with HCV internal ribosome entry site (IRES) around the GCAC motif near the initiator AUG present in the stem region of stem-loop IV (SL IV) (Pudi, R., Abhiman, S., Srinivasan, N., and Das S. (2003) J. Biol. Chem. 278, 12231-12240) [20].

Associations of RRM2 with chemical compounds

• The genes for the M2 subunit of ribonucleotide reductase (RRM2), ornithine decarboxylase (ODC1), and 55,000-Daltons protein (P5), are amplified in hydroxyurea-resistant hamster and human cell lines [2].
• PSF comprises an N-terminal proline- and glutamine-rich domain, two RRMs (RRM1 and RRM2), and a C-terminal region that contains two nuclear localization signals, both of which are required for complete nuclear localization [21].
• Triapine, a new RR inhibitor, was equally potent for p53R2 and hRRM2 [22].
• Of interest, p53R2 was 158-fold more susceptible to the iron chelator deferoxamine mesylate than hRRM2, although the iron content of the two proteins determined by atomic absorption spectrometer was almost the same [22].
• The increase in sensitivity to cisplatin and RNR inhibitors was correlated with the suppression of dATP and dGTP levels caused by stable expression of R2-targeted short interference RNA [3].

Physical interactions of RRM2

• In the present study, we have characterized the functional domains of GRSF-1 and mapped the RNA binding activity of GRSF-1 to RRM 2 (amino acids 194 to 275) with amino-terminal deletion glutathione S-transferase (GST)-GRSF-1 proteins [23].
• The protein is inactive (specific activity 1 x 10(-4) that of wt-R2), which permitted a determination of the pK(a) of the NO(2)Y in the R1/R2 complex in the presence of substrate and effectors [24].

Enzymatic interactions of RRM2

• Mutational analysis indicated that R2 phosphorylated the threonine residue within the T-loop of CDK2 and Cdc2Os1 [25].
• In cells infected with HSV-1 or HSV-2, RR1 had auto- and transphosphorylating activity for the small subunit of HSV ribonucleotide reductase (RR2) and immunoglobulin G (IgG) [26].

Regulatory relationships of RRM2

• When R2 was expressed in budding yeast CAK mutant, the suppression activity in terms of temperature-sensitivity was enhanced by co-expression with Os;cycH;1 [27].
• Peptidomimetic inhibitors that mimic the C-terminal amino acids of R2 inhibit HSV RR by preventing the association of R1 and R2 [28].

Other interactions of RRM2

• Thus, we hypothesize that hRRM2 complements p53R2 to form RR holoenzyme and maintain RR activity in PC3 cells after UV treatment [19].
• RESULTS: RRM1 expression was significantly correlated with PTEN and RRM2 expression in tumor tissue [29].
• Deletion of RRM2 led to a complete loss of speckle localization and resulted in diffuse accumulation of PSF in the nucleus, indicating that RRM2 is required for subnuclear localization [21].
• Truncation of TIAR indicated that the high affinity DNA-binding site overlaps with the RNA-binding site involving RNA recognition motif 2 (RRM2) [30].
• CONCLUSIONS: Taken collectively, TS, USP10, survivin and RRM2 may be useful as prognostic indicators and/or in the development of rationally designed treatment protocols [31].

Analytical, diagnostic and therapeutic context of RRM2

• We demonstrate the ability of systemically administered RRM2 siRNA to suppress tumoral RRM2 expression in an orthotopic xenograft model of pancreatic adenocarcinoma [1].
• The RR activity is consistent with the expression of hRRM2 seen in the Western blots [19].
• Confocal microscopy further confirmed that these findings were not due to translocation of hRRM2 and p53R2 from the cytoplasm to the nucleus [19].
• PCR analysis of the hRRM2 gene promoter confirmed the amplification [32].
• Data are presented from a patient for whom both biopsy and PBMC samples were available, demonstrating applicability of this reproducible, highly sensitive real-time RT-PCR method for the detection and quantification of mRNAs for RRM2 in human WBC and tissue samples [9].

References