The 5′-upstream region of the mouse CPO gene. The nucleotide sequence of the first exon (uppercase letters) and 5′ -upstream regions (−1.2 kb) is demonstrated. White and black arrows indicate the major and the minor transcription initiation sites, respectively. The putative cis-acting GATA, CACCC, and SP-1–like elements are boxed and underlined. The initiating codon is shown in bold and underlined. The intronic sequence is expressed in lowercase letters.