Atce1: A Novel Mouse Cyclic Adenosine 3′,5′-Monophosphate-Responsive Element-Binding Protein-Like Gene Exclusively Expressed in Postmeiotic Spermatids

Members of the ATF/CREB family of transcription factors are involved in gene activation in various physiological systems ranging from metabolite homeostasis, through regulation of cell cycle, to learning and memory. Two members of this family, cAMP-responsive element binding protein (CREB), and cAMP-responsive element modulator (CREM) are active during mammalian spermatogenesis and are required for this process, as has been shown by knockout and dominant negative experiments. In an effort to identify mouse proteins that interact with the testis-specific protein Tctex2, a mouse testis expression library was screened via the two-hybrid system, using the carboxyl-terminal portion of this protein as bait. A clone containing two overlapping open reading frames, related by a frameshift of one nucleotide, was subsequently isolated. The peptide that interacted with Tctex2 does not initiate from a consensus AUG codon, and it is not clear whether it exists physiologically. However, the other reading frame, initiating from an AUG codon, encodes a 315-amino acid peptide with significant sequence homology to a subfamily of the CREB genes whose prototype is the mouse LZIP peptide. This novel CREB-like peptide, designated Atce1, is specifically expressed in the testis. A developmental study using Northern hybridization and in situ hybridization analyses revealed that Atce1 transcripts begin to accumulate in testes of mice 24 d after birth, reflecting expression in mid/late round spermatids. Interestingly, EMSAs revealed that in vitro translated Atce1 binds specifically to a nuclear factor-κB-binding element rather then to a CRE element. Potential roles for Atce1 are discussed.