The biogenesis of a number of RNA species in eukaryotic cells requires 3' processing. To determine the enzymes responsible for these trimming events, we created yeast strains lacking specific 3' to 5' exonucleases. In this work, we describe the analysis of three members of the RNase D family of exonucleases (Rex1p, Rex2p and Rex3p). This work led to three important conclusions. First, each of t...

Mutations in the genes encoding single-strand DNA-specific exonucleases (ssExos) of Escherichia coli were examined for effects on mutation avoidance, UV repair, and conjugational recombination. Our results indicate complex and partially redundant roles for ssExos in these processes. Although biochemical experiments have implicated RecJ exonuclease, Exonuclease I (ExoI), and Exonuclease VII (Exo...

We develop a triple-color fluorescent probe which may function as a lab-on-a-DNA-molecule for simultaneous detection of multiple exonucleases/restriction endonucleases. This triple-color fluorescent probe can be further applied for the discrimination of seven exonucleases and four cell lines as well as the screening of various nuclease inhibitors.

A homopolymer system has been developed to examine the digestion strategies of DNA exonucleases. Escherichia coli exonuclease I and lambda-exonuclease, are processive enzymes. However, T7 exonuclease, spleen exonuclease, E. coli exonuclease III, the 3' leads to 5'-exonuclease of T4 DNA polymerase, and both the 3' leads to 5' and the 5' leads to 3' activity of E. coli DNA polymerase I dissociate...

Recombination of λ red gam phage in recD mutants is unaffected by inactivation of RecJ exonuclease. Since nucleases play redundant roles in E. coli, we inactivated several exonucleases in a recD mutant and discovered that 5’-3’ exonuclease activity of RecJ and exonuclease VII is essential for λ recombination, whereas exonucleases of 3’-5’ polarity are dispensable. The implications of the presen...

Two enzyme activities which release nucleotides preferentially from the 5’ termini of DNA were found in T4-infected Escherichia coli. Since no corresponding activities were found in uninfected cells, the activities appear to be induced by T4. Both activities are capable of excising pyrimidine dimers from ultraviolet-irradiated DNA which has been treated with T4 endonuclease V. One of the activi...

Heterotrimeric RecBCD enzyme unwinds and resects a DNA duplex containing blunt double-stranded ends and directs loading of the strand-exchange protein RecA onto the unwound 3'-ending strand, thereby initiating the majority of recombination in wild-type Escherichia coli. When the enzyme lacks its RecD subunit, the resulting RecBC enzyme, active in recD mutants, is recombination proficient althou...

Rearrangements between tandemly repeated DNA sequences are a common source of genetic instability. Such rearrangements underlie several human genetic diseases. In many organisms, the mismatch-repair (MMR) system functions to stabilize repeats when the repeat unit is short or when sequence imperfections are present between the repeats. We show here that the action of single-stranded DNA (ssDNA) ...