REGULATORY REARRANGEMENTS AND SMG-SENSITIVE ALLELES OF THE C-ELEGANS SEX-DETERMINING GENE TRA-1

The tra-1 gene is the terminal regulator in the sex determination path way in C. elegans, directing all aspects of somatic sexual differentia tion. Recessive loss-of-function (lf) mutations in tra-1 masculinize X X animals (normally somatically female), while dominant gain-of-functi on mutations feminize XO animals (normally male). Most tra-1 (lf) muta tions can be fitted into a simple allelic series of somatic masculiniz ation, but a Small number of If alleles do not fit into this series. H ere we show that three of these mutations are associated with DNA rear rangements 5' to the coding region. One allele is an inversion that ma y be subject to a position effect. We also report the isolation of a n ew class of tra-1 alleles that are responsive to mutations in the smg system of RNA surveillance. We show that two of these express RNAs of aberrant size. We suggest that the smg-sensitive mutations may identif y a carboxy-terminal domain required for negative regulation of tra-1 activity. (C) 1994 Wiley-Liss, inc.