The Statin Target Hmgcr Regulates Energy Metabolism and Food Intake through Central Mechanisms.

The statin drug target, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), is strongly linked to body mass index (BMI), yet how HMGCR influences BMI is not understood. In mammals, studies of peripheral HMGCR have not clearly identified a role in BMI maintenance and, despite considerable central nervous system expression, a function for central HMGCR has not been determined. Similar to mammals, Hmgcr is highly expressed in the brain.

dNTP production is essential for normal postnatal murine heart development.

The building blocks of DNA, dNTPs, can be produced or can be salvaged from deoxyribonucleosides. However, to what extent the absence of dNTP production can be compensated for by the salvage pathway is unknown. Here, we eliminated dNTP synthesis in the mouse heart and skeletal muscle by inactivating ribonucleotide reductase (RNR), a key enzyme for the production of dNTPs, at embryonic day 13.

Trypanosoma brucei thymidine kinase is tandem protein consisting of two homologous parts, which together enable efficient substrate binding.

Trypanosoma brucei causes African sleeping sickness, a disease for which existing chemotherapies are limited by their toxicity or lack of efficacy. We have found that four parasites, including T. brucei, contain genes where two or four thymidine kinase (TK) sequences are fused into a single open reading frame.

Metal binding and activity of ribonucleotide reductase protein R2 mutants: conditions for formation of the mixed manganese-iron cofactor.

Class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis (C. tm.) lacks the tyrosyl radical and uses a Mn(IV)-Fe(III) cluster for cysteinyl radical initiation in the large subunit.

Ribonucleotide reduction is a cytosolic process in mammalian cells independently of DNA damage.

Ribonucleotide reductase provides deoxynucleotides for nuclear and mitochondrial (mt) DNA replication and repair. The mammalian enzyme consists of a catalytic (R1) and a radical-generating (R2 or p53R2) subunit. During S-phase, a R1/R2 complex is the major provider of deoxynucleotides.

p53R2-dependent ribonucleotide reduction provides deoxyribonucleotides in quiescent human fibroblasts in the absence of induced DNA damage.

Human fibroblasts in culture obtain deoxynucleotides by de novo ribonucleotide reduction or by salvage of deoxynucleosides. In cycling cells the de novo pathway dominates, but in quiescent cells the salvage pathway becomes important. Two forms of active mammalian ribonucleotide reductases are known.

Expression, purification, characterization, and in vivo targeting of trypanosome CTP synthetase for treatment of African sleeping sickness.

African sleeping sickness is a fatal disease caused by two parasite subspecies: Trypanosoma brucei gambiense and T. b. rhodesiense.

The involvement of Arg265 of mouse ribonucleotide reductase R2 protein in proton transfer and catalysis.

Ribonucleotide reductase class I enzymes consist of two non-identical subunits, R1 and R2, the latter containing a diiron carboxylate center and a stable tyrosyl radical (Tyr*), both essential for catalysis. Catalysis is known to involve highly conserved amino acid residues covering a range of approximately 35 A and a concerted mechanism involving long range electron transfer, probably coupled to proton transfer. A number of residues involved in electron transfer in both the R1 and R2 proteins have been identified, but no direct model has been presented regarding the proton transfer side of the process.

Chlamydial ribonucleotide reductase: tyrosyl radical function in catalysis replaced by the FeIII-FeIV cluster.

Ribonucleotide reductase (RNR) from Chlamydia trachomatis is a class I RNR composed of proteins R1 and R2. In protein R2, the tyrosine residue harboring the radical that is necessary for catalysis in other class I RNRs is replaced by a phenylalanine. Active C.

Regulation of mammalian ribonucleotide reduction and dNTP pools after DNA damage and in resting cells.

Ribonucleotide reductase (RNR) provides the cell with a balanced supply of deoxyribonucleoside triphosphates (dNTP) for DNA synthesis. In budding yeast DNA damage leads to an up-regulation of RNR activity and an increase in dNTP pools, which are essential for survival. Mammalian cells contain three non-identical subunits of RNR; that is, one homodimeric large subunit, R1, carrying the catalytic site and two variants of the homodimeric small subunit, R2 and the p53-inducible p53R2, each containing a tyrosyl free radical essential for catalysis.

The Schizosaccharomyces pombe replication inhibitor Spd1 regulates ribonucleotide reductase activity and dNTPs by binding to the large Cdc22 subunit.

Ribonucleotide reductase (RNR) is an essential enzyme that provides the cell with a balanced supply of deoxyribonucleoside triphosphates for DNA replication and repair. Mutations that affect the regulation of RNR in yeast and mammalian cells can lead to genetic abnormalities and cell death. We have expressed and purified the components of the RNR system in fission yeast, the large subunit Cdc22p, the small subunit Suc22p, and the replication inhibitor Spd1p.

The ribonucleotide reductase R1 homolog of murine cytomegalovirus is not a functional enzyme subunit but is required for pathogenesis.

Ribonucleotide reductase (RNR) is the key enzyme in the biosynthesis of deoxyribonucleotides. Alpha- and gammaherpesviruses express a functional enzyme, since they code for both the R1 and the R2 subunits. By contrast, betaherpesviruses contain an open reading frame (ORF) with homology to R1, but an ORF for R2 is absent, suggesting that they do not express a functional RNR.

S Phase-specific transcription of the mouse ribonucleotide reductase R2 gene requires both a proximal repressive E2F-binding site and an upstream promoter activating region.

Ribonucleotide reductase is essential for supplying a balanced pool of the four deoxyribonucleotides required for DNA synthesis and repair. The active enzyme consists of two non-identical subunits called proteins R1 and R2. There are multiple levels of regulation of ribonucleotide reductase activity, which is highest during the S and G(2) phases of an unperturbed cell cycle in mammalian cells.

Sequences downstream of the transcription initiation site are important for proper initiation and regulation of mouse ribonucleotide reductase R2 gene transcription.

Ribonucleotide reductase is essential for the synthesis of all four dNTPs required for DNA replication. The enzyme is composed of two proteins, R1 and R2, which are both needed for activity. Expression of the R1 and R2 mRNAs is restricted to the S-phase of the cell cycle, but the R1 and R2 promoters show no obvious sequence homologies that could indicate coordination of transcription.

Mouse ribonucleotide reductase R2 protein: a new target for anaphase-promoting complex-Cdh1-mediated proteolysis.

Ribonucleotide reductase consists of two nonidentical proteins, R1 and R2, and catalyzes the rate-limiting step in DNA precursor synthesis: the reduction of ribonucleotides to deoxyribonucleotides. A strictly balanced supply of deoxyribonucleotides is essential for both accurate DNA replication and repair. Therefore, ribonucleotide reductase activity is under exquisite control both transcriptionally and posttranscriptionally.

Survival of DNA damage in yeast directly depends on increased dNTP levels allowed by relaxed feedback inhibition of ribonucleotide reductase.

In eukaryotes, DNA damage elicits a multifaceted response that includes cell cycle arrest, transcriptional activation of DNA repair genes, and, in multicellular organisms, apoptosis. We demonstrate that in Saccharomyces cerevisiae, DNA damage leads to a 6- to 8-fold increase in dNTP levels. This increase is conferred by an unusual, relaxed dATP feedback inhibition of ribonucleotide reductase (RNR).

Cid13 is a cytoplasmic poly(A) polymerase that regulates ribonucleotide reductase mRNA.

Fission yeast Cid13 and budding yeast Trf4/5 are members of a newly identified nucleotidyltransferase family conserved from yeast to man. Trf4/5 are thought to be essential DNA polymerases. We report that Cid13 is a poly(A) polymerase.

EPR studies on a stable sulfinyl radical observed in the iron-oxygen-reconstituted Y177F/I263C protein R2 double mutant of ribonucleotide reductase from mouse.

Ribonucleotide reductase (RNR) catalyzes the biosynthesis of deoxyribonucleotides. The active enzyme contains a diiron center and a tyrosyl free radical required for enzyme activity. The radical is located at Y177 in the R2 protein of mouse RNR.

Yeast DNA damage-inducible Rnr3 has a very low catalytic activity strongly stimulated after the formation of a cross-talking Rnr1/Rnr3 complex.

The ribonucleotide reductase system in Saccharomyces cerevisiae includes four genes (RNR1 and RNR3 encoding the large subunit and RNR2 and RNR4 encoding the small subunit). RNR3 expression, nearly undetectable during normal growth, is strongly induced by DNA damage. Yet an rnr3 null mutant has no obvious phenotype even under DNA damaging conditions, and the contribution of RNR3 to ribonucleotide reduction is not clear.

Mammalian p53R2 protein forms an active ribonucleotide reductase in vitro with the R1 protein, which is expressed both in resting cells in response to DNA damage and in proliferating cells.

Recently, a homologue of the small subunit of mammalian ribonucleotide reductase (RNR) was discovered, called p53R2. Unlike the well characterized S phase-specific RNR R2 protein, the new form was induced in response to DNA damage by the p53 protein. Because the R2 protein is specifically degraded in late mitosis and absent in G0/G1 cells, the induction of the p53R2 protein may explain how resting cells can obtain deoxyribonucleotides for DNA repair.

A mouse in vitro transcription system reconstituted from highly purified RNA polymerase II, TFIIH and recombinant TBP, TFIIB, TFIIE and TFIIF.

Unregulated transcription of protein-encoding genes in vitro is dependent on 12-subunit core RNA polymerase II and five general transcription factors; TATA binding protein (TBP), transcription factor (TF)IIB, TFIIE, TFIIF, and TFIIH. Here we describe cloning of the mouse cDNAs encoding TFIIB and the small and large TFIIE and TFIIF subunits. The cDNAs have been used to express the corresponding proteins in recombinant form in Escherichia coli and in Sf21 insect cells, and all proteins have been purified to > 90% homogeneity.

The ribonucleotide reductase inhibitor Sml1 is a new target of the Mec1/Rad53 kinase cascade during growth and in response to DNA damage.

The evolutionarily conserved protein kinases Mec1 and Rad53 are required for checkpoint response and growth. Here we show that their role in growth is to remove the ribonucleotide reductase inhibitor Sml1 to ensure DNA replication. Sml1 protein levels fluctuate during the cell cycle, being lowest during S phase.