Two unique 5' untranslated regions in mRNAs encoding human 14-3-3 zeta: differential expression in hemopoietic cells.

In this report, we describe the identification and characterization of a novel 14-3-3 cDNA using the polymerase chain reaction and the screening of a human bone marrow cDNA library. This cDNA encodes the zeta isoform of 14-3-3 and contains a novel 5' untranslated region (UTR) that is G + C rich and only 50% identical to the 5' UTR in the human placental 14-3-3 zeta cDNA, suggesting that 14-3-3 zeta is encoded by at least two mRNAs. Using specific probes to the 5' UTRs of bone marrow and placental 14-3-3 zeta cDNAs, we studied the expression of each transcript in human hemopoietic cells at various stages of differentiation in the myeloid and lymphoid lineages. Differences in the expression of the bone marrow and placental 14-3-3 zeta transcripts were found, the most notable being the markedly decreased expression of both 14-3-3 zeta transcripts in HL-60 myeloid leukemic cells. Western blot analysis of 14-3-3 zeta levels in HL-60 cells revealed correspondingly decreased levels of 14-3-3 zeta protein compared to Jurkat cells. The differences among cell types of relative expression of the two 14-3-3 transcripts may reflect normal regulatory patterns, while the strikingly decreased expression of both types in HL-60 are more likely to be reflective of its multiple genetic abnormalities which contribute to its transformed phenotype.