A 32-base-pair (bp) DNA duplex with deletions in one strand, and thus extra bases in the opposing strand, was ligated head-to-tail to produce linear and circular multimers. The electrophoretic mobility of the linear multimers was analyzed in polyacrylamide gels and the size of the circular DNA was determined by electron microscopy. A 1-base deletion produced a marked retardation in the mobility of the linear multimers coincident with the formation of a population of multimeric circles of a smaller average size than the deletionless 32-mer; 2-, 3-, or 4-base deletions at the same site produced proportionately greater effects. Two 1-base deletions separated by 10 bp on the same strand produced a greater reduction in mobility than a 1-base deletion, whereas two 1-base deletions spaced by 5 bp on the same strand yielded a molecule that behaved more like the deletionless DNA. We conclude that deletions of 1-4 bases at a single site on duplex DNA produce molecules that behave as if they contain sharp bends or kinks. In contrast, single mismatches in the 32-bp duplex produced no abnormality in behavior relative to normally base-paired DNA in the gel mobility and electron microscopic assays. The possible role of such structures in organizing the three-dimensional folding of single-stranded nucleic acids is considered.Extra bases in one strand of double-stranded DNA or RNA may result from a variety of natural mechanisms. When single-stranded RNA or DNA folds on itself, the resulting secondary structure can be thought of as a chain of duplex rods containing perfectly and imperfectly paired bases linked by junctions containing extra bases in one of the two opposing strands. How these junctions contribute to the overall folding of single-stranded DNA or RNA is not established, but were they to provide a precise orientation to the adjoining duplex segments, a possibility raised here, an understanding of their structure would be very important-in particular to our knowledge of the folding of natural RNA.Extra or deleted bases can also be found in duplex DNA as a result of recombination or of errors in replication. In vitro, the RecA protein of Escherichia coli readily catalyzes recombination reactions between two DNAs that differ from each other by a number of bases, giving rise to recombinant heteroduplexes containing base deletions in one strand (1, 2). In vitro studies have suggested how the deletion of bases during replication could lead to frameshift mutations (3), and in vivo, bacteriophage T4 DNA polymerase plays a central role in controlling the frequency of frameshift mutations (4). Deletions or insertions of bases in one strand can result from DNA synthesis in vitro where, in general, single-base deletions predominate and most often occur in runs of the same nucleotide (5-7). In E. coli, the repair of deletions of up to 10 bases in one strand of DNA is carried out by the methyldirected repair system, which also corrects mismatches in DNA (ref. 8, reviewed in ref. 9). To understand how base deletions or inser...

Cytosolic glutathione S-transferases (GSTs) from rat ovaries and testis were purified by a combination of GSH and S-hexylglutathione affinity chromatography. The isolated GSTs were subjected to reverse-phase HPLC, electrospray MS and Nterminal peptide sequencing analysis. The major GST isoenzymes expressed in ovaries are subunits A3, A4, M1, M2 and P1. Other isoenzymes detected are subunits A1, M3 and M6*. In rat testis, the major GST isoenzymes expressed are subunits A3, M1, M2, M3, M5* and M6*. Subunits A1, A4 and P1 are expressed in lesser amounts. We could not detect post-translational

Telomere-to-telomere and gapless reference genome assemblies are necessary to ensure that all genomic variants are studied and discovered, including centromeres, telomeres, AT-rich blocks, mating type loci, biosynthetic, and metabolic gene clusters. Here, we applied long-range sequencing technologies to determine the near-completed genome sequences of four widely used biocontrol agents or biofertilizers: Trichoderma virens Gv29-8 and FT-333, Trichoderma asperellum FT101, and Trichoderma atroviride P1.

Protein arginine methylation often modulates protein-protein interactions. To isolate a sufficient quantity of proteins enriched in methyl arginine(s) from natural sources for biochemical studies is laborious and difficult. We describe here an expression system that produces recombinant proteins that are enriched in v-N G ,N G -asymmetry dimethylarginines. A yeast type I arginine methyltransferase gene (HMT1) is put on a plasmid under the control of the Escherichia coli methionine aminopeptidase promoter for constitutive expression. The protein targeted for post-translational modification is put on the same plasmid behind a T7 promoter for inducible expression of His 6 -tagged proteins. Sbp1p and Stm1p were used as model proteins to examine this expression system. The 13 arginines within the arginine-glycine-rich motif of Sbp1p and the RGG sequence near the C terminus of Stm1p were methylated. Unexpectedly, the arginine residue on the thrombin cleavage site (LVPRGS) of the fusion proteins can also be methylated by Hmt1p. Sbp1p and Sbp1p/hmt1 were covalently attached to solid supports for the isolation of interacting proteins. The results indicate that arginine methylation on Sbp1p exerts both positive and negative effects on protein-protein interaction.