| Activation of pre mRNA splicing by human RNPS 1 is regulated by CK 2 phosphorylation . ^^^ RNPS 1 is phosphorylated in vivo and interacts with the CK 2 ( casein kinase 2 ) protein kinase . ^^^ Serine 53 ( Ser 53 ) of RNPS 1 was identified as the major phosphorylation site for CK 2 in vitro , and the same site is also phosphorylated in vivo . ^^^ We propose that RNPS 1 is a splicing regulator whose activator function is controlled in part by CK 2 phosphorylation . . ^^^ |