The mRNA Encoding τCstF‐64 Is Expressed Ubiquitously in Mouse Tissues

Polyadenylation is a process of endonucleolytic cleavage of the mRNA, followed by addition of up to 250 adenosine residues to the 3′ end of the mRNA. Polyadenylation is essential for eukaryotic mRNA expression, and CstF‐64 is a subunit of the CstF polyadenylation factor that is required for accurate polyadenylation. We discovered that there are two forms of the CstF‐64 protein in mammalian male germ cells, one of which (CstF‐64) is expressed in all tissues, the other of which (τCstF‐64) is expressed only in male germ cells and in brain (albeit at significantly lower levels in the brain). Therefore, we were surprised to find that, using reverse transcription‐PCR, cDNA cloning, and RNA blot analyses, τCstF‐64 mRNA was expressed at higher levels in brain than in testis. Also, τCstF‐64 mRNA was expressed at lower but detectable levels in all tissues tested, including epididymis, heart, kidney, liver, lung, muscle, ovary, spleen, thymus, and uterus. These results suggest the hypothesis that τCstF‐64 mRNA is regulated at the translational or post‐translational level.