The LYL-1 oncoprotein is ubiquitously expressed in the mouse

The lyl-1 gene encodes a protein that belongs to the basic helix-loop-helix (bHLH) family of transcription factors. In humans lyl-1 was first identified as a fusion gene due to a chromosomal translocation found in a subset of T-ALL. Expression of lyl-1 in humans is restricted to hematopoietic cells where it parallels the expression of two related bHLH proteins: SCL/tal-1 and tal-2, both involved in leukemogenesis as well. Expression of lyl-1 in mice and humans is similar. To investigate the role of lyl-1 in mice we first performed a refined analysis of lyl-1 expression by RT-PCR. We examined the following cell lines: two embryonic (NIH-3T3, ES) and one adult (MEL), and the following tissues: lung, kidney, liver, spleen, brain, muscle, heart, ovary, and testis, normal whole embryo and peripheral blood lymphocytes. A 192-bp lyl-1 fragment was amplified in all analyzed samples, suggesting that lyl-1 is ubiquitously expressed in mice. Northern blot analysis confirmed this pattern of expression and evidenced a larger amount of lyl-1 mRNA in the embryo. Furthermore, we performed an antisense oligomer treatment against the starting codon of the translation region of lyl-1 mRNA in MEL cells and embryonic fibroblasts. After 35/48 hours of treatment the cells underwent growth arrest in a dose dependent manner. Taken together these findings show for the first time that lyl-1 is ubiquitously expressed in the mouse, and participates in the control of cell proliferation, suggesting a new role for this transcription factor.