Specific phosphoproteins are targets of numerous extracellular signals received by astrocytes. One such target, which we previously described, is PEA-15, a protein kinase C substrate associated with microtubules. Two cDNAs differing in the length of their 3'-untranslated region (3'UTR) were cloned from a mouse astrocytic library. Accordingly, Northern blots revealed two transcripts (1.7 and 2.5 kilobase pairs) abundant brain regions but also found in peripheral tissues. PEA-15-deduced protein sequence (130 amino acids) shared no similarity with known proteins but is 96% identical to its human counterpart. In addition, several regions of the 3'UTR share more than 90% identity between mouse and human. Different potential regulatory sequences are found in the 3'UTR, which also completely includes the proto-oncogene MAT1. The high level of conservation of both the coding and the untranslated regions and the differential tissular distribution of the two transcripts of this major brain phosphoprotein suggest that not only the protein but also the 3'UTR of PEA-15 mRNA play a role in astrocytic functions.