The interaction and colocalization of Sam 68 with the splicing associated factor YT 521 B in nuclear dots is regulated by the Src family kinase p 59 ( fyn ) . ^^^ The Src family kinase p 59 ( fyn ) mediated tyrosine phosphorylation of Sam 68 negatively regulates its association with YT 521 B , and overexpression of p 59 ( fyn ) dissolves nuclear dots containing YT 521 B . ^^^