CHARACTERIZATION OF A PROLACTIN-INDUCIBLE GENE, CLONE-15, IN T-CELLS

To examine how PRL regulates lymphocyte proliferation, a number of PRL -activated genes were identified from a PRL-dependent rat T lymphoma c ell line, Nb2. One of the downstream genes in the PRL signaling cascad e was identified as clone 15 (c15). PRL stimulation of quiescent Nb2 T cells results in the expression of a 1.7-kilobase c15 mRNA, which rea ches maximum levels between 8 and 10 h after stimulation. Correspondin g [H-3]thymidine incorporation experiments show that the maximum level of c15 mRNA expression correlates with the G1/S transition phase of t he cell cycle. Sequencing of approximately 1.3-kilobase cDNA revealed one open reading frame that predicts a 332-amino acid protein. In vitr o transcription/ translation of c15 cDNA resulted in the production of a 45-kilodalton protein. Sequence analysis revealed that the c15 open reading frame contains a potential nuclear localization signal, a ver y acidic region, and a carboxy-terminal region of 94 amino acids which are 68% identical and 78% similar to the nuclear movement protein, NU DC, found in Aspergillus nidulans. Such a high degree of conservation suggests that the NUDC-like motif in c15 has been conserved through ev olution for an important structure and/or function.