Identification of chURP, a nuclear calmodulin-binding protein related to hnRNP-U

In a screen for myosin-like proteins in embryonic chicken brain, we have id entified a novel nuclear protein structurally related to hnRNP-U (heterogen eous nuclear ribonuclear protein U). We have called this protein chURP, for chicken U-related protein. In this screen, chURP was immunoreactive with t wo myosin antibodies and, in common with the unconventional myosins, bound calmodulin in vitro in both the presence and absence of calcium ions. Deter mination of 757 amino acids of the chURP sequence revealed that it shares 4 1% amino acid identity with human and rat hnRNP-U, although chURP and hnRNP -U appear not to be orthologous proteins. ChURP is ubiquitously expressed i n the nuclei of all chick tissues and, as one of a growing number of calmod ulin-binding proteins to be identified in the nucleus, further highlights t he potential of calmodulin as a regulator of nuclear metabolism.