Role of the Schizosaccharomyces pombe F-box DNA helicase in processing recombination intermediates.

In an effort to identify novel genes involved in recombination repair, we isolated fission yeast Schizosaccharomyces pombe mutants sensitive to methyl methanesulfonate (MMS) and a synthetic lethal with rad2. A gene that complements such mutations was isolated from the S. pombe genomic library, and subsequent analysis identified it as the fbh1 gene encoding the F-box DNA helicase, which is conserved in mammals but not conserved in Saccharomyces cerevisiae. An fbh1 deletion mutant is moderately sensitive to UV, MMS, and ¿ rays. The rhp51 (RAD51 ortholog) mutation is epistatic to fbh1. fbh1 is essential for viability in stationary-phase cells and in the absence of either Srs2 or Rqh1 DNA helicase. In each case, lethality is suppressed by deletion of the recombination gene rhp57. These results suggested that fbh1 acts downstream of rhp51 and rhp57. Following UV irradiation or entry into the stationary phase, nuclear chromosomal domains of the fbh1¿ mutant shrank, and accumulation of some recombination intermediates was suggested by pulsed-field gel electrophoresis. Focus formation of Fbh1 protein was induced by treatment that damages DNA. Thus, the F-box DNA helicase appears to process toxic recombination intermediates, the formation of which is dependent on the function of Rhp51

Effectiveness of Photodynamic Therapy and Nd-YAG Laser Treatment for Obstructed Tracheobronchial Malignancies

Since 1980, advanced lung carcinomas were treated with palliative laser therapy for the purpose of opening the endobronchial stenosis and obstruction by either photodynamic therapy (PDT) or Nd-YAG laser treatment at Tokyo Medical University. A total of 258 lesions were treated, 81 by PDT and 177 by Nd-YAG laser treatment. PDT achieved effective results in 61 (75%) of 81 lesions. In the Nd-YAG laser group, 143 (81%) of 177 lesions showed effective results. When the tumor was located in the trachea or main bronchi, effective results were obtained in 73% (19 of 26) of cases treated by PDT and in 93% of cases (64 of 69) treated by Nd-YAG laser. However, in cases in which the tumor was located in lobar or segmental bronchi, the tumor response was effective in 76% (42 of 55) of PDT-treated patients and 73% (79 of 108) of Nd-YAG laser-treated patients. With a mortality rate of 0%, the greatest advantage of PDT over Nd-YAG treatment was safety. Considering complications, PDT seems to be useful for obstruction of lobar and segmental bronchus. Nevertheless, when deciding among alternative therapies, physicians treating patients with advanced lung carcinoma should give careful consideration to the benefit and complications of both laser therapies and decide the most suitable modality