p210BCR/ABL-induced alteration of pre-mRNA splicing in primary human CD34+ hematopoietic progenitor cells.

Chronic myelogenous leukemia (CML) is a malignancy of the human hematopoietic stem cell (HSC) caused by the p210BCR/ABL oncoprotein. Although alternative splicing of pre-mRNA is a critical determinant of a cell's protein repertoire, it has not been associated with CML pathogenesis. We identified a BCR/ABL-dependent increase in expression of multiple genes involved in pre-mRNA splicing (eg SRPK1, RNA Helicase II/Gu, and hnRNPA2/B1) by subtractive hybridization of cDNA from p210BCR/ABL-eGFP vs eGFP-transduced umbilical cord blood CD34+ cells. beta1-integrin signaling is important to HSC maintenance and proliferation/differentiation, and is abnormal in CML. As an example of how changes in pre-mRNA processing might contribute to CML pathogenesis, we observed alternative splicing of a gene for a beta1-integrin-responsive nonreceptor tyrosine kinase (PYK2), resulting in increased expression of full-length Pyk2 in BCR/ABL-containing cells. Treatment of p210BCR/ABL-positive cells with the Abl-specific tyrosine kinase inhibitor STI571 reverted PYK2 splicing to a configuration more consistent with normal cells, and correlated with decreased expression of BCR/ABL-induced proteins involved in pre-mRNA processing. Whether altered PYK2 splicing contributes to CML pathogenesis remains undetermined; however, we propose that generic changes in pre-mRNA splicing as a result of p210BCR/ABL kinase activity may contribute to CML pathogenesis.