DEG1, encoding the tRNA:pseudouridine synthase Pus3p, impacts HOT1-stimulated recombination in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, HOT1-stimulated recombination has been implicated in maintaining homology between repeated ribosomal RNA genes. The ability of HOT1 to stimulate genetic exchange requires RNA polymerase I transcription across the recombining sequences. The trans-acting nuclear mutation hrm3-1 specifically reduces HOT1-dependent recombination and prevents cell growth at 37 degrees .

Expression of asparagine independence in variants of ICR 2A haploid frog cells.

Properties of the change from asparagine dependence (asn-) to independence (asn+) were investigated in the androgenetic haploid frog cell line ICR 2A. Two types of asn+ variants arose spontaneously during culture. Glutamine-dependent asparagine synthetase (AS) activity, found to be deficient in asn- cells, was repressed by asparagine in one type of variant and expressed constitutively in the other.