| Abstrakt: |
In an effort to produce a more complete transcription map of the short (∼5 Mb) arm of the mouse Y chromosome, we have initiated exon trapping from Yp-derived YACs. Sequence analysis of the trapped products has identified exons of previously cloned mouse Y-located genesZfyandSStyand potential exons homologous to the human Y-locatedTspygene family. In addition, a family of three Yp-located transcripts that show close homology to humanRHOA(locus designation ARHA), a member of the Ras family of small GTPases, has been identified. To determine whether these Yp sequences had been transposed from an autosomal ancestor, we used this trapped product to isolate a full-length autosomal mouseRhoAcDNA that is 80% identical at the nucleotide level and 98% identical at the amino acid level to humanRHOAand maps to mouse Chromosome 2 (locus designationArhA). Sequence analysis indicates that the Y-linked copies have diverged from the autosomal form, with small deletions precluding maintenance of a significant open reading frame in all Yp copies. Yet RT-PCR analysis indicates that two of these pseudogenes,RhoAy1and3,are expressed in a testis-specific manner, in sharp contrast to the nearly ubiquitous expression pattern of the autosomal ancestor. The data indicate that the Y copies ofRhoAhave been transposed from an autosome, followed by subsequent duplication, sequence divergence, and acquisition of a testis-specific promoter/enhancer. |
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