Possible functional role of NSPs in cancer.

Since the discovery of several distinct yet similar cDNA clones encoding novel structural proteins an initiative was taken to investigate their role in tumorigenesis. Sequence analysis revealed that these cDNAs correspond to locus HCMOGT-1 located at chromosome 17p11.2. A total of four isoforms had been isolated. Sequence homology revealed slight similarity to SMC/SbcC ATPase motifs for all isoforms and a CH domain (Calponin-like) in particular for the two 3B isoforms. Sequence analysis of the 3B isoforms, predict a carboxyl terminus with a potential Calcium-dependent actin-binding domain. Expression of NSP 5a3a was high in certain cancer cell lines in-vitro while in others levels were low. Interestingly, in normal tissues, NSP5a3a was found highly expressed in testicular tissue while very low to null in other body tissues. In this study we find most importantly, through siRNA silencing of HCMOGT-1 and proteomic analysis we show that nucleolar phosphoprotein B23, which is involved in mitosis, interacts with both NSP 5a3a and 5a3b, supporting early assumptions of the potential role of these NSP isoforms in cell division for cancer cells and lastly through FACS analysis and siRNA silencing of HCMOGT-1 and NPM1 we elucidate possible roles of NSP 5a3a and 5a3b in cell proliferation and apoptosis with respect to B23.