Bloom syndrome and Werner syndrome are genetic disorders in which an increased rate of chromosomal abnormality is observed. The genes responsible for these diseases, BLM and WRN, have been cloned and identified as homologs of the Escherichia coli recQ genes. We studied the effect of recQ mutations on illegitimate recombination, which is an aberrant biological event related to the chromosomal abnormality in humans, and found that a variety of recQ mutations increased spontaneous illegitimate recombination by 20-to 300-fold and increased UV light-induced illegitimate recombination by 10-to 100-fold. Most bio or pro transducing phages are formed by the recombination events at several hot spots, which are enhanced by the recQ mutation. The analysis of nucleotide sequences at the recombination junction in the transducing phages indicates that recombination at the hot spot sites as well as the non-hot spot sites takes place between short homologous sequences. Enhancement of the recombination in the recQ mutants also occurs in the recA, recBC sbcBC, or recBC sbcA backgrounds, indicating that these recombination events are mediated by none of the known recombination pathways, RecBC, RecF, and RecE. We therefore concluded that the RecQ function suppresses illegitimate recombination that depends on short homologous regions. We discuss a model, based on the 3-to-5 helicase activity of RecQ, to explain the role of this protein as a suppressor of illegitimate recombination.

In connection with the chemical modification of protein, the photooxidation of histidine and N-benzoylhistidine was investigated. It was confirmed that histidine is photooxidized to aspartic acid and urea via several intermediate compounds. The isolation of the intermediates as pure compounds, however, was difficult because of their instability during the purification. In the photooxidation of N-benzoylhistidine also, besides the final products, many kinds of intermediate products were detected and among them 17 compounds were isolated in pure state and characterized. The structures of five compounds were determined, and those of other five compounds were proposed. The same products were obtained when riboflavin or rose bengal instead of methylene blue was used as the photosensitizer in the photooxidation of N-benzoylhistidine though their relative

Several attempts have been made to detect and retrieve fetal nucleated cells including nucleated erythrocytes (NRBCs), leukocytes, and trophoblasts in maternal blood. We have recently developed a new method for non-invasive fetal DNA diagnosis from maternal blood. Peripheral blood granulocytes including NRBCs were isolated by a discontinuous density gradient method using Percoll (Pharmasia). NRBCs were found and retrieved at a single cell level using a micromanipulator under a microscope. To determine whether the origin of the NRBCs was maternal or fetal, the NRBCs were analysed by polymerase chain reaction (PCR) amplification to determine the presence of a Y-chromosome-specific repeat sequence in mothers carrying male fetuses. We were successful in predicting fetal sex accurately in 10 out of 11 samples taken from maternal blood. This new technique opens up fetal DNA diagnosis from maternal blood during the first trimester of pregnancy to the whole population because there is no risk to the fetus or the mother.

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