By subtractive hybridization using single-stranded phagemids with directional inserts, we isolated a mouse cDNA clone, LSM-1, from temperature-sensitive Abelson virus-tranformed immature B cells whose differentiation was being induced after the shift from the permissive (35°C) to the non-permissive temperature (39°C). LSM-1, which encodes an as yet unknown peptide of 197 amino acids, has a putative signal sequence and a trans-membrane region, and is expressed in B- and T-cell lines, in spleen, thymus, and bone marrow of adult mice, and in embryos.
