The functional significance of a lac operator constitutive mutation has been determined. The transition adenine-thymine to guanine-cytosine was shown to be a constitutive mutation simply because thymine contains the functionally important 5-methyl group whereas cytosine does not. The remainder of the base pair is of no consequence. The experimental approach was to synthesize various modified op...

mRNA control networks depend on recognition of specific RNA sequences. Pumilio-fem-3 mRNA binding factor (PUF) RNA-binding proteins achieve that specificity through variations on a conserved scaffold. Saccharomyces cerevisiae Puf3p achieves specificity through an additional binding pocket for a cytosine base upstream of the core RNA recognition site. Here we demonstrate that this chemically sim...

the effect of interactions of various ia and iia cations with two positions of the adenine-thymine (a−t) and guanine-cytosine (g−c) base pairs on the geometries and individual hydrogen bond (hb) energies have been investigated by using the atoms in molecules (aim) method at the b3lyp/6-311++g(d,p) level of theory. the cations that possess higher charge/radius (q/rad) ratio make higher changes o...

Depression of thymidylate synthetase activity by cytosine arabinoside in CCRF-CEM cells was correlated with a blocking of precursor incorporation into RNA and with cell lysis. With increasing concentrations of cytosine arabinoside in the culture media, a proportional decrease of uridine incorporation into RNA and decrease in thymidylate synthetase activity occurred and was accompanied by lysis ...

We have prepared single (N204D) and double (N204D:L272A) mutants of human uracil DNA glycosylase (hUDG), generating two cytosine DNA glycosylases (hCDG and hCYDG). Both these enzymes are able to excise cytosine (but not 5-methylcytosine), when this base is part of a mismatched base pair. hCDG is more active than the equivalent E. coli enzyme (eCYDG) and also has some activity when the cytosine ...

The vibronic spectrum of laser desorbed and jet cooled cytosine consists of bands from two major tautomers (keto and enol) as revealed by UV-UV and IR-UV double resonance spectroscopy and methyl blocking experiments. Only one isomer each was observed for the cytosine dimer and for the cytosine 1-methylcytosine mixed dimer. These isomers form C=O HNH/NH N hydrogen bonds. Cytosine 5-methylcytosin...

The charge density distribution in deuterated cytosine monohydrate [4-(2H2)-amino-2(1H)-(1-2H)-pyrimidinone], C4H2D3N3O.D2O, Mr = 134.15, monoclinic, P2(1)/c, a = 7.714 (1), b = 9.825 (1), c = 7.506 (2) A, beta = 100.52 (1) degrees, Z = 4, has been determined from 1432 X-ray reflections [sin theta/lambda less than 1.15 A-1, Mo K alpha, lambda = 0.7093 (1) A] collected at 82 (2) K. Least-squares...

Ab initio surface hopping dynamics calculations were performed to study the photophysical behavior of cytosine and guanine embedded in DNA using a quantum mechanical/molecular mechanics (QM/MM) approach. It was found that the decay rates of photo excited cytosine and guanine were affected in a completely different way by the hydrogen bonding to the DNA environment. In case of cytosine, the geom...

Epigenetic factors play a role in the expression of virulence traits in Apicomplexa. Apicomplexan genomes encode putative DNA cytosine methylation enzymes. To assess the presence of cytosine methylation of Toxoplasma gondii and Cryptosporidium parvum DNA, we used mass spectrometry analysis and confirmed that these organisms lack detectable methylcytosine in their DNA.