GENERATION OF A TRANSCRIPTION MAP AT THE HSD17B LOCUS CENTROMERIC TO BRCA1 AT 17Q21

A detailed transcription map of the 320-kb region containing the HSD17 B locus on chromosome 17 was generated. Thirty unique cDNA fragments, retrieved following the hybridization of immobilized YACs to primary p ools of cDNAs prepared from RNA of mammary gland, ovary, placenta, and the Caco-2 cell line, were aligned into 10 transcription units by phy sical mapping and hybridization to RNAs of a series of tissues. The cD NAs were then further characterized by sequencing and used to screen m ammary gland cDNA libraries. Fragments corresponding to the broadly ex pressed gamma-tubulin and Ki antigen genes were identified. A full-len gth cDNA clone encoding a 117-amino-acid protein homologous 60 the rat ribosomal protein L34 was isolated. Portions of genes with restricted patterns of expression were also obtained, including the previously c haracterized HSD17B1. One new gene, for which a full-length cDNA was i solated, was found to have an interesting tissue-specific pattern of e xpression with abundant mRNA in both the colon and the testis and in t he mammary carcinoma cell line BT-474. This contrasted with the barely detectable level observed in several tissues including normal mammary gland. Of the five additional transcription units identified, one sho wed no similarity, two showed identity to human expressed sequences, a nd two displayed similarity to genes of animal species by amino acid a lignment. These latter cDNA clones include potential homologues of a r at nuclear tyrosine phosphatase and of a factor of Drosophila that is known to be involved in the negative regulation of transcription of se gment identity genes. (C) 1995 Academic Press, Inc.