Cloning and characterisation of Ifi206: a new murine HIN-200 family member

HIN-200 proteins are interferon-inducible proteins capable of regulating cell growth, senescence, differentiation and death. Using a combination of in silico analysis of NCBI EST databases and screening of murine C57BL/6 cDNA libraries we isolated novel murine HIN-200 cDNAs designated Ifi206S and Ifi206L encoding two putative mRNA splice variants. The p206S and p206L protein isoforms have a modular domain structure consisting of an N-terminal PAAD/DAPIN/Pyrin domain, a region rich in serine, threonine and proline residues and a C-terminal 200 B domain characteristic of other HIN-200 proteins. Ifi206 mRNA was detected only in the spleen and lung of BALB/c and C57BL/6 mice and expression was up-regulated by both types I and II IFN subtypes. p206 protein was predominantly expressed in the cytoplasm and addition of LMB, a CRM1 dependent nuclear export inhibitor, caused p206 to accumulate in the nucleus. Unlike other human and mouse HIN-200 proteins that contain only a single 200 amino acid domain, overexpression of p206 impaired the clonogenic growth of tumour cell lines. Thus, p206 represents the newest HIN-200 family member discovered. It has distinct and restricted pattern of expression however maintains many of the hallmarks of HIN-200 proteins including the presence of a characteristic 200 X domain, induction by interferon and an ability to suppress tumour cell growth.