A gene mapping to the sex-determining region of the mouse Y chromosome is deleted in a line of XY female mice mutant for Tdy, and is expressed at a stage during male gonadal development consistent with its having a role in testis determination. This gene is a member of a new family of at least five mouse genes, related by an amino-acid motif showing homology to other known or putative DNA-binding domains.

The testis-determining gene Siy is located on the short arm of the mouse Y chromosome in a region known to have undergone duplications and rearrangements in comparison with the equivalent portion of the human Y chromosome. Detailed analysis of the Sry genomic locus reveals a further difference in that the mouse Sry open reading frame lies within 2.8 kilobases of unique sequence at the center of a large inverted repeat. This repeat, which is found in both Mus musculus musculus and Mus musculs domesticus Y chromosomes, is not present at the human SRY locus. Recombination involving the repeat region may have led to an lI-kilobase deletion, precisely excising Sry in a line of XY female mice.

SUMMARYThe intact terminal protein genes (TP1 and TP2) of Epstein-Barr virus (EBV) are created upon infection by circularization of the linear viral genome at its terminal repeats. The structure of the 1.7 kb TP2 latent mRNA has been determined by cDNA analysis and Northern blotting, revealing its close relation to TP1 mRNA. The 1.7 kb transcript is expressed from a different promoter and has a different 5' exon from TP1 but is also spliced across the terminal repeats. The last eight exons are common to the TP1 and TP2 RNAs. The TP2 promoter is 3.3 kb downstream of the TP1 promoter and is part of a bidirectional latent EBV promoter region transcribing the TP2 and the latent membrane protein RNAs in opposite directions.

initiate cell migration. We show that, when overexpressed, Cv-2 can weakly antagonise BMP4 activity in Xenopus embryos, but that in other in vitro assays Cv-2 can increase the activity of co-expressed BMP4. Furthermore, we find that increased expression of Cv-2 causes premature onset of trunk neural crest cell migration in the chick embryo, indicative of Cv-2 acting to promote BMP activity at an endogenous site of expression. We therefore propose that BMP signalling is modulated both by antagonists and by Cv-2 that acts to elevate BMP activity.

Five DNA-binding sites for the Epstein-Barr virus BZLF1 protein have been identified within three of the early viral promoters, and four of these binding sites contain a consensus AP-1 site. The part of the BZLF1 protein required for sequence-specific DNA binding to one of these AP-1-like sites was identified by deletion mapping. Site-directed mutagenesis of this DNA target suggests that BZLF1 may work partly by overcoming a cellular repressor of viral transcription.