Genomic organization of the mouse AZ1 gene that encodes the protein localized to preacrosomes of spermatids.

The AZ1 protein is localized to the preacrosome region of spermatids. Previous developmental studies suggested that AZ1 gene transcription begins in pachytene spermatocytes and that expression of the gene is induced in cultivated fibroblasts on treatment with 5-azacytidine, which is known to lead to the demethylation of genomic DNA. In the present study, we cloned the gene coding AZ1 cDNA and elucidated its genomic organization. AZ1 cDNA was encoded by 25 exons distributed within 25 kb of genomic DNA. The transcription started at nucleotide positions -312 and -311 of the cDNA, with the A of the ATG codon specifying the initiator methionine assigned as nucleotide position +1. Exon 1 and a part of intron 1 of the AZ1 gene constituted a typical CpG island, and an about 0.2-kb sequence of the 5'-proximal region exhibited a G + C content and CpG ratio higher than the averages for the mammalian genomic sequence.