Arrested development: understanding v-abl. 
The protein tyrosine kinase activity of the v-abl oncogene has been demonstrated to subvert the normal second messenger systems used by lymphoid cells for growth and differentiation. Transformation of bone marrow with the Abelson murine leukemia virus results in the appearance of B cell lineage cells arrested at the pre-B cell stage. Recent reports have characterized these cells expressing high v-abl kinase activity as deficient in detectable NF-kappaB DNA binding activity and low level RAG gene expression. These observations suggest that v-abl may be inhibiting the differentiation of B cells by blocking these two crucial elements in the maturation pathway.