In systemic autoimmunity, autoantibodies directed against nuclear antigens (Ags) often arise by somatic hypermutation (SHM) that converts AGT and AGC (AGY) Ser codons into Arg codons. This can occur by three different single-base changes. Curiously, AGY Ser codons are far more abundant in complementarity-determining regions (CDRs) of IgV-region genes than expected for random codon use or from s...

Little is known about the natural selection of synonymous codons within the coding sequences of plant genes. We analyzed the distribution of synonymous codons within plant coding sequences and found that preferred codons tend to encode the more conserved and functionally important residues of plant proteins. This was consistent among several synonymous codon families and applied to genes with d...

Protein output from synonymous codons is thought to be equivalent if appropriate tRNAs are sufficiently abundant. Here we show that mRNAs encoding iterated lysine codons, AAA or AAG, differentially impact protein synthesis: insertion of iterated AAA codons into an ORF diminishes protein expression more than insertion of synonymous AAG codons. Kinetic studies in E. coli reveal that differential ...

With the three-letter alphabet [R,Y,N] (R = purine, Y = pyrimidine, N = R or Y), there are 26 codons (NNN being excluded): RNN,...,NNY (six codons at two unspecified bases N), RRN,...,NYY (12 codons at one unspecified base N), RRR,...,YYY (eight specified codons). A statistical methodology that uses the codon frequency and a reduced centered variable leads to similar results for a codon occurre...

The genetic code is degenerate. Each amino acid is encoded by up to six synonymous codons; the choice between these codons influences gene expression. Here, we show that in coding sequences, once a particular codon has been used, subsequent occurrences of the same amino acid do not use codons randomly, but favor codons that use the same tRNA. The effect is pronounced in rapidly induced genes, i...

The genetic code markup is the assignment of stop codons. The standard genetic code markup ensures the maximum possible stability of genetic information with respect to two fault classes: frameshift and nonsense mutations. There are only 528 (about 1,3% of total number) optimal markups in the set of markups having 3 stop codons. Among the sets of markups with 1,2…8 stop codons, the standard cas...

We report the discovery of a simple environmental sensing mechanism for biofilm formation in the bacterium Bacillus subtilis that operates without the involvement of a dedicated RNA or protein. Certain serine codons, the four TCN codons, in the gene for the biofilm repressor SinR caused a lowering of SinR levels under biofilm-inducing conditions. Synonymous substitutions of these TCN codons wit...

The addition of noncanonical amino acids to the genetic code requires unique codons not assigned to the 20 canonical amino acids. Among the 64 triplet codons, only the three nonsense "stop" codons have been used to encode non-native amino acids. Use of quadruplet "frame-shift" suppressor codons provides an abundant alternative but suffers from low suppression efficiency as a result of competing...

We previously employed a combinatorial approach to identify the most efficient suppressors of four-base codons in E. coli. We have now examined the suppression of two-, three-, four-, five-, and six-base codons with tRNAs containing 6-10 nt in their anticodon loops. We found that the E. coli translational machinery tolerates codons of 3-5 bases and that tRNAs with 6-10 nt anticodon loops can su...