APOBEC3G (A3G) is a host-expressed protein that inactivates retroviruses through the mutagenic deamination of cytosines (C) to uracils (U) in single-stranded DNA (ssDNA) replication products. A3G prefers to deaminate cytosines preceded by a cytosine (5'CC), whereas all other A3 proteins target cytosines in a 5'TC motifs. Structural and mutational studies have mapped the dinucleotide deamination...

The modified base, 5-methylcytosine, constitutes approximately 1% of human DNA, but sites containing 5-methylcytosine account for at least 30% of all germline and somatic point mutations. A genetic assay with a sensitivity of 1 in 10(7), based on reversion to neomycin resistance of a mutant pSV2-neo plasmid, was utilized to determine and compare the deamination rates of 5-methylcytosine and cyt...

Zea and Tripsacum nuclear ribosomal internal transcribed spacer (ITS) sequences were used to evaluate patterns of concerted evolution, rates of substitutions, patterns of methylation-induced deamination, and structural constraints of the ITS. ITS pseudogenes were identified by their phylogenetic position, differences in nucleotide composition, extensive deamination at ancestral methylation site...

A previous st,udy on the metabolism of amphetamine (1-phenyl-2-aminopropane), widely used as a stimulant of the central nervous system, showed that its major route of biotransformation in the rat and dog involved hydroxylation of the aromatic ring. In the rabbit, however, the compound was not hydroxylated, but was found to be transformed in another manner (2). The present report describes an en...

8-Nitro-cGMP is an endogenous nucleotide discovered under inflammation conditions as an important mediator of nitric oxide (NO) signaling. Besides cGMP-like behaviour, 8-nitro-cGMP exerts unique cytoprotective effects against oxidative stress. Although the formation of 8-nitro-cGMP from 8-nitro-GTP has previously been proposed, the mechanism by which excess or unused 8-nitro-cGMP is removed fro...

Activation-induced (cytidine) deaminase (AID) efficiently introduces multiple and diversified deaminations in immunoglobulin (Ig) variable and switch regions. Here, we review studies of AID, and the APOBEC family member, APOBEC3G, demonstrating that both enzymes introduce multiple deaminations by processive action on single-stranded DNA and that deaminations occur stochastically at hot- and col...

The yeast Saccharomyces cerevisiae is able to use para-aminobenzoic acid (pABA) in addition to 4-hydroxybenzoic acid as a precursor of coenzyme Q, a redox lipid essential to the function of the mitochondrial respiratory chain. The biosynthesis of coenzyme Q from pABA requires a deamination reaction at position C4 of the benzene ring to substitute the amino group with an hydroxyl group. We show ...

Deamination of deoxycytidylate, deoxyguanylate, and deoxyadenylate, as well as deoxyadenosine and deoxyguanosine, by rat liver and several hepatomas was studied by a method based on the determination by a Conway diffusion technic of the am monia formed. Several factors affecting the enzyme reactions were considered, and the application of the method to the estimation of deaminase activity in ti...

APOBEC3G (A3G) is a host-encoded protein that potently restricts the infectivity of a broad range of retroviruses. This can occur by mechanisms dependent on catalytic activity, resulting in the mutagenic deamination of nascent viral cDNA, and/or by other means that are independent of its catalytic activity. It is not yet known to what extent deamination-independent processes contribute to the o...

G x C-->A x T transitions within T-C or C-C bipyrimidine sequences are by far the most frequent class of mutation induced by 254-nm UV irradiation in most genes and species investigated, but the reason for the high degree of mutability and specificity at these sites is uncertain. Some data implicate the deamination of cytosine to uracil as a possible cause, but other results appear to indicate ...