Developmental Defects and Male Sterility in Mice Lacking the Ubiquitin-Like DNA Repair Gene mHR23B

Abstract

mHR23B encodes one of the two mammalian homologs of Saccharomyces cerevisiae RAD23, a ubiquitin-like fusion protein involved in nucleotide excision repair (NER). Part of mHR23B is complexed with the XPC protein, and this heterodimer functions as the main damage detector and initiator of global genome NER. While XPC defects exist in humans and mice, mutations for mHR23A and mHR23B are not known. Here, we present a mouse model for mHR23B. Unlike XPC-deficient cells, mHR23B^−/− mouse embryonic fibroblasts are not UV sensitive and retain the repair characteristics of wild-type cells. In agreement with the results of in vitro repair studies, this indicates that mHR23A can functionally replace mHR23B in NER. Unexpectedly, mHR23B^−/− mice show impaired embryonic development and a high rate (90%) of intrauterine or neonatal death. Surviving animals display a variety of abnormalities, including retarded growth, facial dysmorphology, and male sterility. Such abnormalities are not observed in XPC and other NER-deficient mouse mutants and point to a separate function of mHR23B in development. This function may involve regulation of protein stability via the ubiquitin/proteasome pathway and is not or only in part compensated for by mHR23A.

We thank C. Vermeij-Keers for helpful discussions on mHR23B mutant embryos and R. Hendriks for enzyme-linked immunosorbent assay and fluorescence-activated cell sorter experiments.

This work was partially supported by The Netherlands Organization for Scientific Research (NWO) (grant SIR 15-2777 and grant TF004 for Diseases of the Elderly), NIH (grant AG17242-02), KWF (EUR 98-1774), and the Dutch Foundation “Vereniging Trustfonds Erasmus Universiteit Rotterdam.” This work was also supported by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan and by the Biodesign Research Program and the Bioarchitect Research Project from RIKEN.