Search

Szumskyj, Benjamin, ed. Fritz Leiber: Critical Essays. Jefferson: McFarland, 2008. 207 pp. Sofftcover. ISBN 978-0-7864-2972-1. $35. A new analysis of the body of work of speculative fiction grand master Fritz [...]

Nucleotide excision repair proteins have been implicated in genetic recombination by experiments in Saccharomyces cerevisiae and Drosophila melanogaster, but their role, if any, in mammalian cells is undefined. To investigate the role of the nucleotide excision repair gene ERCC1, the hamster homologue to the S. cerevisiae RADIO gene, we disabled the gene by targeted knockout. Partial tandem duplications of the adenine phosphoribosyltransferase (APRT) gene then were constructed at the endogenous APRT locus in [ERCC1.sup.-] and [ERCC1.sup.+] cells. To detect the full spectrum of gene-altering events, we used a loss-of-function assay in which the parental [APRT.sup.+] tandem duplication could give rise to [APRT.sup.-] cells by homologous recombination, gene rearrangement, or point mutation. Measurement of rates and analysis of individual [APRT.sup.-] products indicated that gene rearrangements (principally deletions) were increased at least 50-fold, whereas homologous recombination was affected little. The formation of deletions is not caused by a general effect of the ERCC1 deficiency on gene stability, because [ERCC1.sup.-] cell lines with a single wild-type copy of the APRT gene yielded no increase in deletions. Thus, deletion formation is dependent on the tandem duplication, and presumably the process of homologous recombination. Recombination-dependent deletion formation in [ERCC1.sup.-] cells is supported by a significant decrease in a particular class of crossover products that are thought to arise by repair of a heteroduplex intermediate in recombination. We suggest that the ERCC1 gene product in mammalian cells is involved in the processing of heteroduplex intermediates in recombination and that the misprocessed intermediates in [ERCC1.sup.-] cells are repaired by illegitimate recombination.

The XpF/Ercc1 structure‐specific endonuclease performs the 5′ incision in nucleotide excision repair and is the apparent mammalian counterpart of the Rad1/Rad10 endonuclease from Saccharomyces cerevisiae. In yeast, Rad1/Rad10 endonuclease also functions in mitotic recombination. To determine whether XpF/Ercc1 endonuclease has a similar role in mitotic recombination, we targeted the APRT locus in Chinese hamster ovary ERCC1+ and ERCC1− cell lines with insertion vectors having long or short terminal non‐homologies flanking each side of a double‐strand break. No substantial differences were evident in overall recombination frequencies, in contrast to results from targeting experiments in yeast. However, profound differences were observed in types of APRT+ recombinants recovered from ERCC1− cells using targeting vectors with long terminal non‐homologies—almost complete ablation of gap repair and single‐reciprocal exchange events, and generation of a new class of aberrant insertion/deletion recombinants absent in ERCC1+ cells. These results represent the first demonstration of a requirement for ERCC1 in targeted homologous recombination in mammalian cells, specifically in removal of long non‐homologous tails from invading homologous strands. [ABSTRACT FROM AUTHOR]

Discusses the influences of author M.R. James on the writings of Fritz Leiber. James' stories as the impetus for writing the short story `The Pale Brown Thing'; Utilization of philosophy on the writing of spectral stories first expounded by James.