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Zinc finger genes represent a large multigene family present in mammalian and other genomes. A subgroup of these genes contain a conserved motif, the KRAB domain, at the NH2-terminal region, which was recently shown to posses a potent transcriptional repression activity. For one such gene, ZNF45, we determined the complete coding sequence, along with the exon/intron arrangement and the splice junctions. Exon 2 codes exclusively for the KRAB-A element of 42 amino acids, and exon 4 contains the 19 zinc finger repeats. In addition, we generated an EST (expressed sequence tag) from the 3’-end of ZNF45 that we used for polymerase chain reaction screening of a Pl-derived genomic library. We isolated a 65-kb clone that was used for localizing this gene on chromosome 19ql 3.2 by fluorescence in situ hybridization.

We have developed a procedure for efficient in situ hybridization of bacterial recombinants created with various types of large-insert cloning vectors. Minimal quantities of crude DNA are amplified and labeled during the degenerate-oligonucleotide-primed polymerase chain reaction. The resulting probes generate high-intensity fluorescent hybridization signals on metaphase chromosomes and on interphase nuclei.