Figure 4.

Comparison of full length and short form Stk. The Mst1r gene generates a full length transcript which encodes Stk, a tyrosine kinase that serves as the cell surface receptor for macrophage stimulating protein (MSP). The Mst1r gene also uses an internal promoter (Pro2) to encode a short form of Stk (sf-Stk), which lacks the MSP binding domain and whose function is unknown. Strains of mice resistant to SFFV-induced erythroleukemia do not encode sf-Stk due to a 3 bp deletion in the internal promoter. Although sf-Stk lacks a signal sequence, it is shown in the membrane for comparison.