Characterization of the testes-specific pim-1 transcript in rat

The plm-1 proto-oncogene encodes a serine/threonine protein klnase and is expressed in cells of hematolymphoid origin and in the germ cell lineages. In somatic cells, the plm-1 gene is expressed as a 2.8 kb transcript while a shorter sized transcript (2.3 kb) is expressed in rat testes. We have determined that the shorter testes-specificplm-1 transcript arises through the use of an alternate polyadenylation signal present in the 3′ untranslated region of the gene. This alternate polyadenylation event results in the removal of an A/U-rich regulatory element located in the 3′ untranslated region of the plm-1 gene. This A/U-rlch motif has been shown by a number of laboratories to destabilize the transcripts of genes that contain this sequence. Consistent with these findings, we have demonstrated that the shortened testes-specific plm-1 transcript is more stable than the longer A/U-rich containing somatic transcript. We suggest that the functional significance of different sized plm-1 transcripts may be directly related to their different stabilities and that the greater stability of the testes-specific transcript may be essential for the translational delay observed in postmeiotlc male germ cells.